WO2001068082A1

WO2001068082A1 - Treatment and/or prevention of ocular pain

Info

Publication number: WO2001068082A1
Application number: PCT/AU2001/000284
Authority: WO
Inventors: Paul Mendell Erickson; Timo Martti Tapio Tervo; Carlos Belmonte; Juana Gallar
Original assignee: Unisearch Limited
Priority date: 2000-03-15
Filing date: 2001-03-15
Publication date: 2001-09-20
Also published as: AUPQ622600A0

Abstract

The present invention provides a pharmaceutical composition for the treatment and/or prevention of ocular pain and/or inflammatory reactions in the eye of a vertebrate, wherein said composition comprises capsaicin or an analogue thereof, or mixture thereof, and at least one anaesthetic. There is also provided a method for the treatment and/or prevention of ocular pain and/or inflammatory reactions in the eye of a vertebrate, wherein said method comprises administering to said eye a therapeutically effective amount of capsaicin or an analogue thereof or a mixture thereof, wherein prior to the administration of said capsaicin or an analogue thereof or mixture thereof, the eye is pretreated with a therapeutically effective amount of at least one anaesthetic.

Description

Treatment and/or Prevention of Ocular Pain

Technical Field

The present invention relates to the treatment and or prevention of pain, discomfort, itch or inflammatory reaction of the eye and conjunctiva, particularly those derived of ocular surgery, contact lens wearing, dry eye and inflammatory processes of the front of the eye.

Background Art

Pain is a well known phenomenon as an indicator of injury or tissue damage due to inflammation, ischaemia, mechanical or other irritation. The first step leading to the sensation of pain is the activation of nociceptive primary afferents by intense thermal, mechanical or chemical stimuli. Indirect studies of nociceptive transduction (activation) indicate that it involves chemical mediators that are released or synthesised in response to tissue damage (Fields & Levine, 1984).

Anaesthetics block neuronal transmission and affect sensation as well as pain. For example, analgesics act by interfering with the activity of chemical mediators without affecting sensory input. Local anaesthetics are substances that block ion channels in nerve terminals and/or parent axons of nociceptor nerve fibres blocking the conduction of pain nerve impulses to the central nervous system. Most local anaesthetics are tertiary amines that block the sodium channels in the nerve interrupting the production of action potentials by nerve fibres in the tissues that are directly exposed to the anaesthetic.

Capsaicin (trøπs-8-Methyl-N-vanillyl-6-nonenamide) is the pungent ingredient of red peppers. In the vertebrate eye, low concentrations of capsaicin produces a strong activation of ocular sensory nerves, accompanied by intense pain and ocular irritation. Capsaicin has the unique ability to induce intense excitation of nociceptor nerve fibres, and a subsequent long-term impairment of the mechanism for transmitting chemosensitive and thermal pain in vertebrates (desensitisation).

These effects of capsaicin have been used for acute reduction of pain in the skin and joints in humans by topical application of creams containing capsaicin (Νolano, et al. 1999) or injection of the substance into the joint (Brady, et al. 1997). However, whilst local anaesthetics and capsaicin have been used to acutely reduce existing pain in skin and joints, nowhere is it suggested, nor would it be expected, that in the presence of a blockade of nerve activation with a local anaesthetic (an agent which prevents the generation of nerve impulses in sensory nerve terminals), that the neuropeptide depleting and desensitising effects of capsaicin would still persist. The present invention allows the combination of a local anaesthetic with capsaicin to produce a temporal functional denervation which will prevent pain and neurogenic inflammation the eye and ocular adnexa that are expected to occur by application of surgical or other therapeutical procedures, while the acute pain-producing effects of capsaicin are blocked by pretreatment with a local anaesthetic.

Accordingly, the present invention resides in the unexpected finding that blockade of nerve signals evoked by capsaicin with a local anaesthetic, although preventing the acute pain producing effect of capsaicin, does not eliminate its long term desensitising effects, nor the depletion of neuropeptides contained in nerve terminals which cause neurogenic inflammation. This allows the combination of a local anaesthetic with capsaicin to produce a temporal functional denervation which will prevent pain and neurogenic inflammation of the eye and ocular adnexa, symptoms that are associated with ocular pain.

Therefore, the present invention provides a useful therapeutic in the treatment and/or prevention of pain, discomfort, itch or inflammatory reaction of the eye and conjunctiva, particularly those derived of ocular surgery, contact lens wearing, dry eye and inflammatory processes of the front of the eye.

Disclosure of the Invention

According to a first embodiment of the invention, there is provided a pharmaceutical composition for the treatment and/or prevention of ocular pain and/or inflammatory reactions in the eye of a vertebrate, wherein said composition comprises capsaicin or an analogue thereof or mixture thereof, together with at least one anaesthetic.

In one form of the invention, when administering the composition as defined in accordance with the first embodiment of the invention for the treatment and/or prevention of ocular pain and/or inflammatory reactions, the composition is typically administered to the front of the eye, ocular adnexa or conjunctiva of the vertebrate.

Typically, the pharmaceutical composition as defined in accordance with the first embodiment of the invention further comprises a pharmaceutically acceptable carrier, adjuvant and/or diluent. According to a second embodiment of the invention, there is provided a method for the treatment and/or prevention of ocular pain and/or inflammatory reactions in the eye of a vertebrate in need of said treatment and or prevention, wherein said method comprises administering to said eye a therapeutically effective amount of capsaicin or an analogue thereof or a mixture thereof, wherein prior to the administration of said capsaicin or an analogue thereof or mixture thereof, the eye is pre-treated with a therapeutically effective amount of at least one anaesthetic.

According to a third embodiment of the invention, there is provided capsaicin or an analogue thereof or mixture thereof, when used in the treatment and or prevention of ocular pain and/or inflammatory reactions in the eye of a vertebrate in need of said treatment and/or prevention, wherein prior to administration of said capsaicin or an analogue thereof or mixture thereof to said eye, the eye is pre-treated with a therapeutically effective amount of at least one anaesthetic.

According to a fourth embodiment of the invention, there is provided the use of capsaicin or an analogue thereof or mixture thereof, for the manufacture of a medicament for the treatment and/or prevention of ocular pain and/or inflammatory reactions in the eye of a vertebrate in need of said treatment and/or prevention, wherein prior to administration of said medicament to said eye, the eye is pre-treated with a therapeutically effective amount of at least one anaesthetic. According to a fifth embodiment of the invention, there is provided the use of capsaicin or an analogue thereof or mixture thereof, together with at least one anaesthetic for the manufacture of a medicament for the treatment and/or prevention of ocular pain and/or inflammatory reactions in the eye of a vertebrate in need of said treatment and or prevention. According to a sixth embodiment of the invention, there is provided a method for the treatment and/or prevention of ocular pain and/or inflammatory reactions in the eye of a vertebrate in need of said treatment and/or prevention, wherein said method comprises administering to said eye a therapeutically effective amount of the composition as defined in accordance with the first embodiment of the invention. According to a seventh embodiment of the invention, there is provided the composition as defined in accordance with the first embodiment of the invention when used in the treatment and/or prevention of ocular pain and/or inflammatory reactions in the eye of a vertebrate in need of said treatment and/or prevention.

According to an eighth embodiment of the invention, there is provided the use of the composition as defined in accordance with the first embodiment of the invention in the manufacture of a medicament for the treatment and/or prevention of ocular pain and/or inflammatory reactions in the eye of a vertebrate in need of said treatment and/or prevention.

Typically, the present invention acts to prevent discomfort, pain, itch and/or inflammation derived of ocular and palpebral surgery, eye manipulations and/or fitting of contact lenses. Also, the procedure of the present invention can additionally be used for treatment of pain and or discomfort accompanying chronic diseases that produce irritation and pain arising from the anterior segment of the eye and conjunctiva such as dry eye, allergic conjunctivitis and other ocular diseases that course with these symptoms, together with pain, itch and/or inflammation derived of ocular and palpebral surgery, eye manipulations and/or fitting of contact lenses.

More typically, the desensitising and anti-inflammatory effect of topical capsaicin is reversible.

In accordance with any one of the second, third, fourth or fifth embodiments of the invention, two compositions, a first composition comprising at least one anaesthetic followed by a second composition comprising at least capsaicin or a capsaicin analogue or mixture thereof, are administered to the front of the eye, ocular adnexa or conjunctiva of the vertebrate.

Typically, the first composition comprises a solution of local anaesthetic in a pharmaceutical acceptable medium for topical ocular application which is effective to suppress pain induced by capsaicin. Typically, the second composition comprises a solution of capsaicin or capsaicin analogue or mixture thereof, in a pharmaceutical acceptable medium suitable for topical ocular application, which is effective in a) depleting neuropeptides from corneal nerves in the isolated cornea, b) reducing sensitivity of the cornea to noxious mechanical and chemical stimulation. The administration of these compositions is typically done in an amount effective to reduce or eliminate pain or discomfort evoked by subsequent ocular surgery or contact lens fitting and to reduce, inhibit or eliminate conjunctival, lid and corneal inflammatory signs caused by these procedures. In a particularly preferred form of the invention a single composition is used, wherein the capsaicin topical formulation additionally contains the anaesthetic and the suitable topical vehicle for the anaesthetic, and this combined pharmaceutical composition is used to prevent and/or treat ocular pain. In this regard, the formulation comprises a topical vehicle for the administration to the vertebrate (particularly human) eye of capsaicin or capsaicin analogue or mixture thereof, together with a anaesthetic, wherein the components of the formulation are present in amounts effective to reduce or eliminate pain or discomfort evoked by subsequent ocular surgery or contact lens fitting and to reduce, inhibit or eliminate conjunctival, lid and corneal inflammatory signs caused by these procedures. Typically, capsaicin is in the form of tr n^-δ-Methyl-N-vanillyl-ό-nonenamide. Typically, the capsaicin analogues include those outlined in Wrigglesworth et al.

(1996), the disclosure of which is incorporated herein by reference. More typically, the capsaicin analogues include: N-(4-(2-Aminoethoxy)-3-methoxybenzyl)-N'-(2-(4- chlorophenyl)ethyl)thiourea and N-(4-(2-Aminoethoxy)-3-methoxybenzyl)-N'-(4-tert- butylbenzyl)thiourea.

Typically, the anaesthetic is a local anaesthetic. More typically, the anaesthetic is selected from the group consisting of: lidocaine, lignocaine, morphine, tetracaine, procaine, bupivacaine, oxybuprocaine, proparacaine, benzocaine, and cocaine.

Typically, in accordance with the first embodiment of the invention, the composition is formulated as a liquid, gel, cream, suspension or ocular colirium.

Similarly, in the capsaicin treatment and/or prevention as outlined in the second, third, fourth or fifth embodiments of the invention, the capsaicin or analogue or mixture thereof or anaesthetic is formulated as a liquid, gel, cream, suspension or ocular colirium.

Typically, the capsaicin treatment and/or prevention as outlined in the second through to eighth embodiments of the invention involves application to the vertebrate eye in the form of a lotion, cream, liposomes or drops. More typically, the capsaicin treatment and/or prevention as outlined in the second through to eighth embodiments of the invention, is applied to the vertebrate eye via a physical applicator, such as an eye drop device. Typically, the vertebrate is selected from the group consisting of human, non- human primate, murine, bovine, ovine, equine, caprine, leporine, avian, feline and canine. More typically, the vertebrate is human, non-human primate or murine. Even more typically, the vertebrate is human.

Definitions A "therapeutically effective amount", in reference to the prevention and/or treatment of ocular pain and/or inflammatory reactions in the eye of a vertebrate refers to an amount sufficient to result in the prevention, cessation or reduction in ocular pain and/or inflammatory reactions in the eye of a vertebrate. Typically, a therapeutic amount is sufficient to result in one or more or the following: prevention of discomfort, pain, itch and or inflammation derived of ocular and palpebral surgery, eye manipulations and fitting of contact lenses, or an amount sufficient to result in reduction or cessation of discomfort accompanying chronic diseases that produce irritation and pain arising from the anterior segment of the eye and conjunctiva such as dry eye, allergic conjunctivitis and other ocular diseases that course with these symptoms, or the reduction or cessation of pain, itch and/or inflammation derived of ocular and palpebral surgery, eye manipulations and fitting of contact lenses.

In the context of this specification, the term "comprising" means "including principally, but not necessarily solely". Furthermore, variations of the word "comprising", such as "comprise" and "comprises", have correspondingly varied meanings.

Brief Description of the Drawings Figure 1: illustrates the intensity-response curves for selective response to mechanical (A), chemical (B), hot (C) and cold (D) stimulation of the cornea 30 minutes after ocular capsaicin treatment (OC). Intensity was measured with a visual analogue scale (NAS) from 0 to 10 by control (squares) and capsaicin-treated (circles) subjects. Data are mean ± SEM, n=5. Inset: linear regression analysis of the data represented in each figure; thin line: control, thick line: after OC. Figure 2: illustrates the intensity-response curves for selective response to mechanical (A), chemical (B), hot (C) and cold (D) stimulation of the cornea one day after ocular capsaicin treatment (OC). Intensity was measured with a visual analogue scale (NAS) from 0 to 10 by control (squares) and capsaicin-treated (circles) subjects. Data are mean ± SEM, n=5. Inset: linear regression analysis of the data represented in each figure; thin line: control, thick line: after OC. Figure 3: illustrates the intensity-response curves for selective response to mechanical (A), chemical (B), hot (C) and cold (D) stimulation of the cornea one week after ocular capsaicin treatment (OC). Intensity was measured with a visual analogue scale (NAS) from 0 to 10 by control (squares) and capsaicin-treated (circles) subjects. Data are mean ± SEM, n=5. Inset: linear regression analysis of the data represented in each figure; thin line: control, thick line: after OC.

Figure 4: illustrates the calcitonin-gene-related peptide (CGRP) release induced by two applications of capsaicin (33 mM) repeated with one hour interval. One drop of 5% lignocaine was applied to the eye 10 minutes before the first capsaicin application. Data are mean ± SD, n = 8 corneas.

Best Mode of Performing the Invention

Pain is a well known phenomenon as an indicator of injury or tissue damage due to inflammation, ischaemia, mechanical or other irritation. The first step leading to the sensation of pain is the activation of nociceptive primary afferents by intense thermal, mechanical or chemical stimuli. Indirect studies of nociceptive activation indicate that it involves chemical mediators that are released or synthesised in response to tissue damage (Fields & Levine, 1984). These chemical mediators include acid, hypertonic saline, 5- hydroxytryptamine, potassium chloride, acetylcholine, purines or bradykinin, and are referred to as algesic agents, recent years it has been shown that prostaglandins and leukotrienes can contribute to the activation of primary afferent nociceptors (Fields & Levine, 1984). Prostaglandins are distinguished from the other chemical mediators in that they induce a state of hyperalgesia by elevating the sensitivity of pain receptors to other painful or algesic stimuli thus enhancing the pain signals sent to the central nervous system.

The stimulation of primary afferents leads to action potentials in their axons, which propagate to the spinal cord. In addition, excited primary afferents release neuropeptides such as substance P (SP), calcitonin-gene-related peptide (CGRP) and neurokinin A (NKA) at their peripheral terminals. Neuropeptides enhance inflammatory reactions in the injured tissue, contributing to vasodilatation, oedema, and increased vascular permeability; this phenomenon is called 'neurogenic inflammation'. The development of pain and its intensity and the degree of neurogenic inflammation are roughly proportional to the number of nerve impulses fired by individual nociceptive fibres and to the number of fibres recruited by the stimulus. In the spinal cord, the nociceptors enter the gray matter of the superficial dorsal horn to synapse on nerve cells contributing to pain-transmission pathways such as the spinothalamic and spinoreticulothalamic tracts, which terminate in two separate regions in the thalamus. The two thalamic regions in turn project to different cortical sites (Fields & Levine, 1984). Anaesthetics block neuronal transmission and affect sensation as well as pain.

Analgesics act by interfering with the activity of chemical mediators without affecting sensory input. According to Remington's Pharmaceutical Sciences, 17th Ed., analgesics can be classified as falling into at least three loose groups: 1) the opiate-based (narcotic) analgesics; 2) the non-opiate analgesics; and 3) analgesics and antipyretics. The opiate-based analgesics include opium derived alkaloids, including morphine, codeine, and their various derivatives, opiate antagonists, the several morphine derivatives which have morphine antagonist activity, but have analgesic activity. Since these narcotic type drugs are addictive, a number of non-addictive, non-opiate analgesics have been developed in an attempt to produce an analgesic, which is highly efficient but not addictive. In the third broad category, the analgesics and antipyretics, are the salicylates and acetaldehyde-containing compounds and the so-called non-steroidal anti- inflammatory drugs. They are non-addictive painkillers. As to their mode of action, drugs that block perception of pain may be said to act either centrally (such as narcotics) or peripherally. Centrally acting narcotic drugs are true analgesics because they can relieve pain regardless of the aetiology.

The non-steroidal anti-inflammatory agents (NSAIAS) have been described as peripheral pain relievers. The action of NSAIAs as pain relievers is associated with the biosynthesis of prostanoids. Inflammation or trauma and resultant tissue injuries cause the release of arachidonic acid, which is degraded by cyclo-oxygenase and lipoxygenase. The cyclo-oxygenase pathway leads to the synthesis of prostaglandin E2 (PGE2) and other mediators. PGE2 release increases the cyclic AMP and ionic calcium levels at the nociceptor membrane resulting in a lowered activation threshold, resulting in the relay to the central nervous system of augmented pain perception (hyperalgesia). Inhibitors of prostaglandin synthesis, such as NSAIAs, act avoiding the sensitising effects of prostaglandins on nociceptive endings and therefore, the decrease in pain threshold.

Local anaesthetics are substances that block ion channels in nerve terminals and or parent axons of nociceptor nerve fibres blocking the conduction of pain nerve impulses to the central nervous system. Most local anaesthetics are tertiary amines that block the sodium channels in the nerve interrupting the production of action potentials by nerve fibres in the tissues that are directly exposed to the anaesthetic.

As described above, capsaicin (trαns-8-Methyl-N-vamllyl-6-nonenamide) induces intense excitation of nociceptor nerve fibres and a subsequent long-tenn impairment of the mechanism for transmitting chemosensitive and thermal pain in animals. Low concentrations of capsaicin in the vertebrate eye, produces a strong activation of ocular sensory nerves, accompanied by intense pain and ocular irritation. This is followed by an acute desensitisation to further applications of capsaicin (Behnonte, et al, 1991). At very high concentrations, capsaicin produces nerve desensitisation to other types of stimuli (Buck, et al., 1983). The effects of capsaicin are due to activation by this substance of a vanilloid receptor (NR1) (Caterina, 1997), which leads to the entrance of calcium ions into the nerve endings. This in turn produces an inactivation of the ionic mechanisms involved in the generation of action potentials by the nerves and the induction of an acute release of SP, CGRP and ΝKA from sensory nerve terminals, leading to long-lasting depletion of their neuropeptide content (Maggi, 1995).

Whilst these effects of capsaicin have been used for acute reduction of pain in the skin and joints by topical application of creams containing capsaicin (Νolano, et al., 1999), or the chronic neuralgia associated with the herpes zoster opthalmicus (Liesegang, 1991) in humans injection of the substance into the joint (Brady, et al, 1997), nowhere is it disclosed, nor would it be expected that in the presence of a blockade of nerve activation with an anaesthetic, an agent which prevents the generation of nerve impulses in sensory nerve terminals, that the neuropeptide depleting and desensitising effects of capsaicin still persist.

This unexpected finding that blockade of nerve signals evoked by capsaicin with a local anaesthetic, although preventing the acute pain producing effect of capsaicin, does not eliminate its long term desensitising effects, nor the depletion of neuropeptides contained in nerve terminals which cause neurogenic inflammation, allows the combination of a local anaesthetic with capsaicin to produce a temporal functional denervation. This temporal functional denervation prevents pain and neurogenic inflammation the eye and ocular adnexa that are expected to occur by application of surgical or other therapeutical procedures, while the acute pain-producing effects of capsaicin are blocked by pretreatment with a local anaesthetic.

The present invention reflects the unexpected finding that local anaesthesia which prevents the activation of nerves and acute pain evoked by topical capsaicin, does not interfere with the capsaicin-induced depletion of neuropeptides in corneal nerves. The preventive reduction of nerve excitability and of the neurogenic inflammatory response evoked by subsequent noxious stimuli will also prevent the development of pain and inflammation following injurious manipulations of ocular tissues and ocular adnexa.

Therefore, in one form, the invention is directed to the use of the acute, reversible desensitising and anti-inflammatory effect of topical capsaicin after preventing its acute pain-producing action via the application of local anaesthetic, either as a separate application or in combination with capsaicin in the form of a composition, as a method to prevent ocular pain and inflammatory reactions induced by processes such as surgery on the anterior segment of the human eye and conjunctiva or discomfort associated with the fitting of corneal lenses. The procedure can additionally be used for treatment of discomfort accompanying chronic diseases that produce irritation and pain arising from the anterior segment of the eye and conjunctiva such as dry eye, allergic conjunctivitis and other ocular diseases that course with these symptoms.

Accordingly, the application of the composition of the present invention produces a temporal functional denervation of the front of the eye of mammals to induce a reduced sensitivity and a reduced ocular inflammatory reaction of the front of the eye to external or internal noxious stimuli. In one form of the invention, this is carried out by administering to vertebrate subjects a topical anaesthetic drug that prevents the acute pain caused by capsaicin and capsaicin analogues followed by, or simultaneously with, topical capsaicin or a capsaicin analogue or mixture thereof, at a dose effective to reduce sensory responses in ocular nerves leading to pain and neurogenic inflammation resulting of the liberation of neuropeptides consecutive to the excitation of the said nerves.

In one example, human clinical trials undertaken in connection with the present invention have established that capsaicin is effective with prior topical anaesthetic application to the eye in appropriate concentrations and vehicle in reducing the intensity of pain and irritative components of the sensation evoked by controlled mechanical and chemical stimuli applied to the cornea one to six days after capsaicin administration. Accordingly, in one form of the invention, topical application of oxybuprocaine in appropriate concentrations and vehicle prior to the ocular application of capsaicin prevents the severe stinging, burning and itching acutely induced by capsaicin application. Typically, in another form of the invention, compositions of the invention are administered to a patient already experiencing ocular pain, in an amount sufficient to cure or at least partially arrest the pain and discomfort. Single or multiple administrations of the pharmaceutical compositions can be carried out with dose levels and pattern being selected by the treating physician. Regardless, the pharmaceutical composition of the present invention should provide a quantity of capsaicin or an analogue thereof, sufficient to effectively treat the patient.

The therapeutically effective dose level for any particular patient will depend upon a variety of factors including: the disorder being treated and the severity of the disorder; activity of the capsaicin or an analogue thereof employed; the composition employed; the age, body weight, general health, sex and diet of the patient; the time of administration; the route of administration; the duration of the treatment; drugs used in combination or coincidental with the capsaicin or an analogue thereof, together with other related factors well known in medicine. For example, it is well known in the art to begin doses of a therapeutic compound, at levels lower than those required to achieve the desired therapeutic effect and to gradually increase the dosage until the desired effect is achieved.

Therefore, one skilled in the art would be able, by routine experimentation, to determine an effective, non-toxic amount of capsaicin or an analogue thereof or mixture thereof, which would be required to treat or prevent ocular pain and or inflammatory reactions. Generally, however, an effective dosage of capsaicin or an analogue thereof or mixture thereof is expected to be in a concentration range of between the following ranges: about O.OlmM to about 400mM, about O.OlmM to about 300mM, about O.OlmM to about 250mM, about O.OlmM to about 200mM, about O.OlmM to about 175mM, about O.OlmM to about 150mM, about O.OlmM to about 125mM, or about O.OlmM to about lOOmM; more typically, about 0.05mM to about 400mM, about 0.05mM to about 300mM, about 0.05mM to about 250mM, about 0.05mM to about 200mM, about 0.05mM to about 175mM, about 0.05mM to about 150mM, about 0.05mM to about 125mM, or about 0.05mM to about lOOmM; even more typically, about O.lmM to about 400mM, about O.lmM to about 300mM, about O.lmM to about 250mM, about O.lmM to about 200mM, about O.lmM to about 175mM, about O.lmM to about 150mM, about O.lmM to about 125mM, or about O.lmM to about lOOmM; yet even more typically, about 0.5 to about 400mM, about 0.5mM to about 300mM, about 0.5mM to about 250mM, about 0.5mM to about 200mM, about 0.5mM to about 175mM, about 0.5mM to about 150mM, about 0.5mM to about 125mM, or about 0.5mM to about lOOmM; still more typically, about lmM to about 400mM, about ImM to about 300mM, about ImM to about 250mM, about ImM to about 200mM, about ImM to about 175mM, about ImM to about 150mM, about ImM to about 125mM, or about ImM to about lOOmM; yet still more typically, about 5mM to about 175mM, about 5mM to about 300mM, about 5mM to about 250mM, about 5mM to about 200mM, about 5mM to about 175mM, about 5mM to about 150mM, about 5mM to about 125mM, or about 5mM to about lOOmM; even more typically, about lOmM to about 400mM, about lOmM to about 300mM, about lOmM to about 250mM, about lOmM to about 200mM, about lOmM to about 175mM, about lOmM to about 150mM, about lOmM to about 125mM, or about lOmM to about lOOmM; still more typically, about 15mM to about 400mM, about 15mM to about 300mM, about 15mM to about 250mM, about 15mM to about 200mM, about 15mM to about 175mM, about 15mM to about 150mM, about 15mM to about 125mM, or about 15mM to about lOOmM; and even more typically, about 30mM to about 400mM, about 30mM to about 300mM, about 30mM to about 250mM, about 30mM to about 200mM, about 30mM to about 175mM, about 30mM to about 150mM, about 30mM to about 125mM, or about 30mM to about lOOmM. Typically, an effective dosage of capsaicin or an analogue thereof or mixture thereof is between the following ranges: about 2 to about 12 drops, about 2 to about 10 drops, about 2 to about 8 drops, about 2 to about 6 drops, about 2 to about 4 drops. More typically, an effective dosage of capsaicin or an analogue thereof or mixture thereof is about 2 drops. Further, if desired, the effective dose of the capsaicin or a capsaicin analogue or mixture thereof may be divided into multiple doses for purposes of administration.

Typically the treatment would be for the duration of the condition, and contact times would typically be for the duration of the condition. Further, it will be apparent to one of ordinary skill in the art that the optimal quantity and spacing of individual dosages of a composition of the present invention will be determined by the nature and extent of the condition being treated, the form, route and site of administration, and the nature of the particular vertebrate being treated. Also, such optimum conditions can be determined by conventional techniques. It will also be apparent to one of ordinary skill in the art that the optimal course of treatment, such as, the number of doses of the compound of the present invention given per day for a defined number of days, can be ascertained by those skilled in the art using conventional course of treatment determination tests.

Typically, the duration of the desensitising and anti-inflammatory effect of the present invention is ideally suited for example to the time course of acute pain which follows photorefractive keratectomy (El-Maghraby, et al, 1999) and to the time course of substantial discomfort associated with the adaptation to rigid gas permeable contact lenses (Bennett, et al., 1997). Further, examples of the duration of the desensitising and anti- inflammatory effect of the present invention are provided in Table 1. Typically, the duration of the desensitising and anti-inflammatory effect of the present invention lasts about 20 days; more typically, the duration is about 14 days; even more typically, about 10 days; and still more typically, about 7 days.

The topical formulations of this invention typically contain a) the compound capsaicin, a chemical derivative of vanillyl amide (8-methyl-N-vanillyl-6-nonenamide) in a concentration effective to reduce the sensitivity of the eye, palpebral conjunctiva and lids to noxious stimulation induced by surgical procedures or application of contact lenses. The pharmaceutical formulation preferably contains this substance in a suitable topical vehicle in the concentrations outlined above. These preferred concentration ranges correspond to bioavailable forms of capsaicin within the formulation as outlined above. If other capsaicin-analogue substances are included in the formulation then different concentrations may be utilised. Clinical studies have shown that such concentrations of capsaicin in a single application are generally effective to desensitise the cornea and conjunctiva for several days without causing any significant visible damage to the eye or conjunctiva. Furthermore, routine clinical testing of corneal and conjunctival sensitivity and exploration of inflammatory signs in the surface of the eye described below can be readily used to optimise capsaicin and anaesthetic concentrations and to establish if lower or higher concentrations are appropriate for a given formulation.

Typically, the amount of anaesthetic present in the composition in accordance with the first, sixth, seventh or eighth embodiments of the invention, or when pre-applied separately to the eye in accordance with the second, third, fourth or fifth embodiments of the invention, is an amount capable of preventing pain induced by capsaicin. Typically, the anaesthetic is present in an amount of between the following ranges: about 0.05 to about 30% w/w, 0.05 to about 25% w/w, 0.05 to about 20% w/w, 0.05 to about 15% w/w, or 0.05 to about 10% w/w; more typically, between about 0.1 to about 30% w/w, 0.1 to about 25% w/w, 0.1 to about 20% w/w, 0.1 to about 15% w/w, or 0.1 to about 10% w/w; even more typically, between about 0.5 to about 30% w/w, 0.5 to about 25% w/w, 0.5 to about 20% w/w, 0.5 to about 15% w/w, or 0.5 to about 10% w/w; still even more typically, between about 1 to about 30% w/w, 1 to about 25% w/w, 1 to about 20% w/w,

1 to about 15% w/w, or 1 to about 10% w/w. Typically, an effective dosage of anaesthetic is between the following ranges: about

2 to about 12 drops, about 2 to about 10 drops, about 2 to about 8 drops, about 2 to about 6 drops, about 2 to about 4 drops. More typically, an effective dosage of anaesthetic is about 2 drops.

Typically, in undertaking the method of the present invention in accordance with the second, third or fourth embodiments of the invention, the pre-treatment of the eye with a therapeutically effective amount of anaesthetic is performed between about 1 to about 20 minutes before the administration of the capsaicin or a capsaicin analogue or mixture thereof. More typically, between about 1 to about 15 minutes. Even more typically, between about 2 to about 15 minutes. Still more typically, between about 2 to about 10 minutes. Yet still more typically, between about 3 to about 10 minutes. Yet even still more typically, between about 3 to about 6 minutes, and even more typically, between about 3 to about 4 minutes.

Also included within the scope of the present invention are prodrugs of the inventive compound. Typically, prodrugs will be functional derivatives of capsaicin or an analogue thereof, which are readily converted in vivo to the required composition for use in the present invention as described herein. Typical procedures for the selection and preparation of prodrugs are known to those of skill in the art and are described, for instance, in H. Bundgaard (Ed), Design of Prodrugs, Elsevier, 1985, the contents of which are incorporated herein by reference. The pharmaceutical composition of the invention can be administered by standard routes, fn general, the combinations may be administered by the topical route. The pharmaceutical composition of the invention may be in the form suitable for administration in the form of an ointment, cream or lotion suitable for topical administration, or in a form suitable for delivery as an eye drop.

The capsaicin component of the invention is typically incorporated into the pharmaceutical compositions by mixing an appropriate amount of a powder presentation of the substance into the chosen formulation vehicle, along with a local anaesthetic drug as desired. The carriers, diluents and adjuvants must be "acceptable" in terms of being compatible with the other ingredients of the formulation, and not deleterious to the recipient thereof. Examples of pharmaceutically and veterinarily acceptable carriers or diluents are demineralised or distilled water; saline solution; vegetable based oils such as peanut oil, safflower oil, olive oil, cottonseed oil, maize oil, sesame oils such as peanut oil, safflower oil, olive oil, cottonseed oil, maize oil, sesame oil, arachis oil or coconut oil; silicone oils, including polysiloxanes, such as methyl polysiloxane, phenyl polysiloxane and methylphenyl polysolpoxane; volatile silicones; mineral oils such as liquid paraffin, soft paraffin or squalane; cellulose derivatives such as methyl cellulose, ethyl cellulose, carboxymethylcellulose, sodium carboxymethylcellulose or hydroxypropylmethylcellulose; lower alkanols, for example ethanol or iso-propanol; lower aralkanols; lower polyalkylene glycols or lower alkylene glycols, for example polyethylene glycol, polypropylene glycol, ethylene glycol, propylene glycol, 1,3- butylene glycol or glycerin; fatty acid esters such as isopropyl palmitate, isopropyl myristate or ethyl oleate; polyvinylpyrridone; agar; carrageenan; gum tragacanth or gum acacia, and petroleum jelly. Suitable topical vehicles for use with the formulations of the invention are well known in pharmaceutical arts and include such vehicles and vehicle components as water; organic solvents such as alcohols, glycols (such as glycerin), mixtures of water and organic solvents (such as water and alcohol) and mixtures of organic solvents (such as alcohol and glycerine); lipid-based materials such as fatty acids, acylglycerols (including oils such as mineral oil and fats of natural or synthetic origin), phosphoglycerides. sphingolipids and waxes; protein-based materials such as collagen and gelatin; silicone- based materials (both non-volatile and volatile) such as cyclomethicone. demethiconol and dimethicone copolyol (Dow Corning); hydrocarbon-based materials such as petrolatum and squalane; anionic, cationic and amphoteric surfactants and soaps; sustained-release vehicles such as microsponges and polymer matrices; stabilising and suspending agents; emulsifying agents; and other vehicles and vehicle components that are suitable for administration to the eye as well as mixtures of topical vehicle components as identified above or otherwise known to the art. The vehicle may further include components adapted to improve the stability or effectiveness of the applied formulation, such as preservatives, antioxidants, cornea penetration enhancers, sustained release materials and the like. Examples of such vehicles and vehicle components are well known in the art and are described in such reference works as Martindale- The Extra Pharmacopoeia (Pharmaceutical Press. London 1993) and Martin (ed.). Remington's Pharmaceutical Sciences, the disclosure of which is incorporated herein by reference. Typically, the carrier or carriers will form from about 10% to about 99.9% by weight of the composition. Still more typically, from 20% to about 99.9% by weight of the composition. Even more typically, from 30% to about 99.9% by weight of the composition. Yet more typically, from 35% to about 99.9% by weight of the composition. Yet still more typically, from 40% to about 99.9% by weight of the composition. Still more typically, from 45% to about 99.9% by weight of the composition, and even more typically, from 50% to about 99.9% by weight of the composition.

The choice of a suitable vehicle will depend on the particular physical form and mode of delivery that the formulation is to achieve. Examples of suitable forms include liquids (including dissolved forms of the substances of the invention as well as suspensions, emulsions and the like) solids and semisolids such as gels, foams, pastes, creams, ointments and the like; formulations containing liposomes or other delivery vesicles

For example, drops according to the present invention may comprise sterile aqueous or oily solutions or suspensions. These may be prepared by dissolving the active ingredient in an aqueous solution of a bactericidal and/or fungicidal agent and/or any other suitable preservative, and optionally including a surface active agent. The resulting solution may then be clarified by filtration, transferred to a suitable container and sterilised. Sterilisation may be achieved by: autoclaving or maintaining at 90°C-100°C for half an hour, or by filtration, followed by transfer to a container by an aseptic technique. Examples of bactericidal and fungicidal agents suitable for inclusion in the drops are phenylmercuric nitrate or acetate (0.002%), benzalkonium chloride (0.01%>) and chlorhexidine acetate (0.01%). Suitable solvents for the preparation of an oily solution include glycerol, diluted alcohol and propylene glycol.

Lotions according to the present invention include those suitable for application to the eye. An eye lotion may comprise a sterile aqueous solution optionally containing a bactericide and may be prepared by methods similar to those described above in relation to the preparation of drops.

Creams, ointments or pastes according to the present invention are semi-solid formulations of the active ingredient for external application. They may be made by mixing the active ingredient in finely-divided or powdered form, alone or in solution or suspension in an aqueous or non-aqueous fluid, with a greasy or non-greasy basis. The basis may comprise hydrocarbons such as hard, soft or liquid paraffin, glycerol, beeswax, a metallic soap; a mucilage; an oil of natural origin such as almond, corn, arachis, castor or olive oil; wool fat or its derivatives, or a fatty acid such as stearic or oleic acid together with an alcohol such as propylene glycol or macrogols.

The pharmaceutical compositions of the invention may incorporate any suitable surfactant such as an anionic, cationic or non-ionic surfactant such as sorbitan esters or polyoxyethylene derivatives thereof. Suspending agents such as natural gums, cellulose derivatives or inorganic materials such as silicaceous silicas, and other ingredients such as lanolin, may also be included.

The pharmaceutical compositions of the invention may also be administered in the foπn of liposomes. Liposomes are generally derived from phospholipids or other lipid substances, and are formed by mono- or multi-lamellar hydrated liquid crystals that are dispersed in an aqueous medium. Any non-toxic, physiologically acceptable and metabohsable lipid capable of forming liposomes can be used. The formulations of the present invention in liposome form may contain, in addition to a compound of the present invention, stabilisers, preservatives, excipients and the like. The preferred lipids are the phospholipids and the phosphatidyl cholines (lecithins), both natural and synthetic. Methods to form liposomes are known in the art, and in relation to this specific reference is made to: Prescott, Ed., Methods in Cell Biology, Nolume XIN, Academic Press, New York, N.Y. (1976), p. 33 et seq., the contents of which is incorporated herein by reference.

In a preferred form the pharmaceutical composition of the invention comprises an effective amount of the capsaicin or a capsaicin analogue or mixture thereof and at least one anaesthetic, together with a pharmaceutically acceptable carrier, diluent and/or adjuvant as shown in Examples 1 to 5.

The invention will now be described in greater detail by reference to specific Examples, which should not be construed as in any way limiting the scope of the invention. The pain reducing and anti-inflammatory efficacy of the formulations of the present invention were tested and confirmed in numerous clinical trials and experimental studies, the results of which are described in the examples below. While these examples further illustrate various aspects and preferred embodiments of the invention as described herein, they are examples only, and should not be considered as limiting the scope of the invention. Examples

Example 1

Effect of capsaicin on human corneal sensitivity

Capsaicin exposure

A mixture of 5.5% (183 n M) oleoresin capsicum (OC), 30.5% isobutane and 64% isopropylalcohol (pepper spray, Capstum^®, Zarc International Inc., Maryland, USA) was sprayed onto the face of five police officers who served as volunteers at a distance of 1.5 to 2.5 meters. The exposure lasted for 0.5 to 1.5 seconds. After the OC exposure the face was washed with cold water and soap during 5 to 15 minutes. This first aid reduced the intensity of the pain. A medical doctor was available during the exposure and first aid periods.

Non-contact gas esthesiometry

Corneal sensitivity was tested unilaterally in human volunteers with a gas esthesiometer that allows selective mechanical, chemical and thermal stimulation of the cornea (Belmonte, 1999). Gas jets of 3s-duration were applied to the corneal surface with 2-min intervals. Mechanical stimulation consisted of a series of pulses of warmed air applied at variable flow rates (0 to 300 ml/min). Chemical stimulation was performed with series of pulses of a warmed mixture of air and CO₂ at different concentrations (0 to 80% CO₂). Selective thermal stimulation consisted of pulses of air, warmed or cooled up to different temperatures in the nozzle of the probe (from -10° to +80°C, inducing changes in corneal surface temperature between -5°C and +3°C). To prevent mechanical stimulation during selective chemical and thermal stimulation, flows below mechanical threshold of each subject were used. To avoid changes in basal corneal temperature during selective mechanical and chemical stimulation, the gas stream was heated up to 50°C at the tip of the probe.

Subjects seated in front of a slit lamp, with the head supported at the head holder. With the slit lamp table commands, the tip of the gas esthesiometer was adjusted at a distance of 5 mm perpendicular to the centre of the cornea. The subject was asked to blink immediately before each stimulus. A click produced by the opening of the valve in the probe identified the onset of the stimulus. Selective mechanical, chemical and thermal stimulation was performed in the left eye in each session. The protocol included three sessions, performed 30 min, 24 hours and 1 week after OC exposure.

Immediately after each stimulation pulse, subjects judged the intensity of the sensation in a 10-cm continuous horizontal scale (visual analog scale, NAS) (Price, 1994), were 0 was assigned to "no sensation" and 10 to "maximal sensation ever experienced". Results: Sensation threshold

Thirty minutes after OC, mechanical sensitivity was still present in all studied subjects, but the average mechanical threshold was significantly higher than control (Table 1) and remained slightly higher 1 day and 1 week after OC.

Threshold for CO stimulation was not significantly modified 30 min after OC

(Table 1). One day later, sensitivity to CO₂ pulses was present only in 3 out of 5 subjects.

In these 3 subjects, CO₂ threshold was significantly higher than control values (Table 1). One of the two subjects with no response to CO₂ recovered chemical sensitivity one week after OC.

Sensitivity to heat had disappeared in 2 out of 5 subjects 30 min after OC, but threshold for hot stimulation of the remaining 3 individuals was normal (Table 1). Similar results were obtained one day and one week after capsaicin (Table 1). Cold sensitivity and cold threshold were unaffected by OC (Table 1).

Stimulus-response curves

Mechanical stimulation. The NAS values of intensity of the sensation reported for increasing stimulus forces were lower than control 30 min after OC (Fig. 1A). One day and 1 week after capsaicin, the intensity curve for mechanical stimulation was still deviated to the right in comparison with control conditions (Figs. 2A and 3A).

Chemical stimulation, hi control conditions, values given to the intensity of the sensation increased with the concentration of CO₂ in the applied stimulus (Fig. IB). Thirty minutes after OC, subjects reported higher NAS values for all values of CO₂ concentration (Fig. IB). Twenty four hours after capsaicin, there was no response in two individuals whereas the intensity-response curve to chemical stimulation of the remaining three remained shifted to the left for the highest CO₂ concentration values (Fig. 4B), and was back to control values one week after OC (Fig. 3B).

Hot air. Thirty minutes after OC exposure, no response to hot stimulation was obtained in 2 out of 5 subjects. NAS values reported by the remaining three subjects were similar to control values (Fig. IC). Twenty four hours after OC, responsiveness to hot air was present in 2 out of 5 subjects, being the average NAS values lower than in control situation (Fig. 2C). One week after capsaicin, values of the response to hot air were slightly lower than in control (Fig. 3C).

Cold air. Intensity-response curves obtained with cold stimulation of the cornea were not modified by OC exposure (Figs. ID, 2D, 3D).

Example 2 Irritative effects of capsaicin in the human eye following pretreatment with a local anaesthetic

Local anaesthetic exposure Four drops of an ophthalmic colirium containing 0.4% oxybuprocaine were applied to both eyes of 3 volunteer subjects. Capsaicin exposure

Three to four min after topical application of the local anaesthetic a mixture of 5.5% (183 mM) oleoresin capsicum (OC), 30.5% isobutane and 64% isopropylalcohol (pepper spray, Capstum^®, Zarc International Inc., Maryland, USA) was sprayed onto the face of five police officers who served as volunteers at a distance of 1.5 to 2.5 metres. The exposure lasted for 0.5 to 1.5 seconds. After the OC exposure the face was washed with cold water and soap during 5 to 15 minutes. This first aid reduced the intensity of the pain. A medical doctor was available during the exposure and first aid periods. Νon-contact gas esthesiometry

Corneal sensitivity was tested unilaterally in human volunteers with a gas esthesiometer that allows selective mechanical, chemical and thermal stimulation of the cornea (Belmonte, 1999). Gas jets of 3s-duration were applied to the corneal surface with 2-min intervals. Mechanical stimulation consisted of a series of pulses of warmed air applied at variable flow rates (0 to 300 ml/min). Chemical stimulation was performed with series of pulses of a warmed mixture of air and CO₂ at different concentrations (0 to 80% CO₂). Selective thermal stimulation consisted of pulses of air, warmed or cooled up to different temperatures in the nozzle of the probe (from -10° to +80°C, inducing changes in corneal surface temperature between -5°C and +3°C). To prevent mechanical stimulation during selective chemical and thermal stimulation, flows below mechanical threshold of each subject were used. To avoid changes in basal corneal temperature during selective mechanical and chemical stimulation, the gas stream was heated up to 50°C at the tip of the probe. Subjects seated in front of a slit lamp, with the head supported at the head holder. With the slit lamp table commands, the tip of the gas esthesiometer was adjusted at a distance of 5 mm perpendicular to the centre of the cornea. The subject was asked to blink immediately before each stimulus. A click produced by the opening of the valve in the probe identified the onset of the stimulus. Selective mechanical, chemical and thermal stimulation was performed in the left eye in each session. The protocol included three sessions, performed 30 min, 24 hours and 1 week after OC exposure.

Immediately after each stimulation pulse, subjects judged the intensity of the sensation in a 10-cm continuous horizontal scale (visual analog scale, NAS) (Price, 1994), were 0 was assigned to "no sensation" and 10 to "maximal sensation ever experienced". Results: Acute effects of capsaicin

No blepharospasm was induced by OC in subjects pre-treated with the local anaesthetic and subjects were able to maintain the eyes open for more than 10 seconds after applying the drug. A second OC exposure performed in one subject 15 minutes later evoked an intense ocular pain, tearing and redness. Subjects were not able to maintain the eyes open and first aid care was applied. Sensation threshold

Sixty minutes after OC, mechanical sensitivity was still present in all studied subjects, but the average mechanical threshold was significantly higher than control and remained slightly higher 1 day and 1 week after OC. Threshold for CO₂ stimulation was significantly higher than control values. Cold sensitivity and cold threshold were unaffected by OC. Stimulus-response curves Mechanical stimulation. The NAS values of intensity of the sensation reported for increasing stimulus forces were lower than control 60 min after OC. One day and 1 week after capsaicin, the intensity curve for mechanical stimulation was still deviated to the right in comparison with control conditions.

Chemical stimulation. Sixty minutes after OC, subjects reported higher NAS values for all values of CO₂ concentration. Twenty-four hours later, there was no response the intensity-response curve to chemical stimulation remained shifted to the left.

Hot air. Sixty minutes after OC exposure, response to hot stimulation was greatly diminished. Twenty-four hours after OC the average NAS values were lower than in control situation. Cold air. Intensity-response curves obtained with cold stimulation of the cornea were not modified by OC exposure.

Example 3 In vitro CGRP release induced by capsaicin in anaesthetised mice corneas Mice were topically treated with 5% lidocaine in both eyes. Five minutes later, they were anaesthetised with 80 mg/Kg ketamine and 10 mg/Kg xylacine i.p. Under microscope, corneas were excised. Mice were sacrificed afterwards. Corneas were placed in tubes containing buffered saline solution (SS) for 5 min. Then, corneas were incubated for 5 min in tubes containing 33 mM capsaicin and changed thereafter to SS. Sixty minutes later, corneas were again exposed to 33 mM capsaicin for 5 min and kept in SS for 10 additional min. At established times, 100 μl samples were taken from the incubation fluid. Concentration of CGRP (calcitonin-gene-related peptide) in the samples was measured by enzyme immunometric assay (EIA)

Detennination of CGRP: One hundred microlitres of samples and CGRP standards (7.81-1000 pg/ml) were added to 96 well-plates coated with monoclonal antibody specific to CGRP. An Acetylcholinesterase-conjugated anti-CGRP antibody was used to selectively bind the CGRP molecules, which bind to the wells. The concentration of CGRP was determined by measuring the enzymatic activity of AChE acting on Ellman's reagent to form a yellow compound. The intensity of yellow colour was determined by spectrophotometry at 414 nm. All procedures were done at room temperature.

Basal CGRP release was 11.28 ± 7.49 pg/min (n = 8). CGRP release was significantly increased to 42.43 ± 18.3 pg/min (p=0.003, paired t-test) 5 min after exposure to 33 mM capsaicin, representing an average increase of 3.8 times the basal CGRP release. CGRP concentration decreased gradually after afterwards, reaching basal values 20 min after capsaicin.

One hour after capsaicin application, CGRP release was 0.10 ± 0.01 pg/min. A second exposure to capsaicin for 5 min induced a CGRP release of 0.6 ± 0.01 pg/min (p=0.001, paired t-test).

Example 4 Capsaicin or an analogue thereof or a mixture thereof may be administered alone, although it is preferable that it be administered as a pharmaceutical formulation. The active ingredient may comprise, for topical administration, from 0.001% to 10% by weight, eg., from 1% to 5% by weight of the formulation, although it may comprise as much as 10% by weight but preferably not in excess of 5% by weight, and more preferably from 0.1% to 1% by weight of the formulation. Further, prior to administration of the capsaicin formulation to the eye, the eye is pre-treated with an effective amount of a local anaesthetic, preferably, proparacaine.

In accordance with the detailed description of the invention provided herein specific preferred pharmaceutical compositions of the present invention are provided hereinafter. The following specific formulations are to be construed as merely illustrative examples of formulations and not as a limitation of the scope of the present invention in any way.

Example 4(a) - Topical Cream Composition

A typical composition for delivery as a topical cream is outlined below: 8-methyl-N-vanillyl-6-noneamide 1.0 g

Polawax GP 200 28.0 g

Lanolin Anhydrous 2.50 g

White Beeswax 4.8 g

Methyl hydroxybenzoate 0.2 g Isotonic saline to 100.0 g

The polawax, beeswax and lanolin are heated together at 60°C, a solution of methyl hydroxybenzoate is added and homogenisation is achieved using high speed stirring. The temperature is then allowed to fall to 50°C. 8-methyl-N-vanillyl-6-noneamide is then added and dispersed throughout, and the composition is allowed to cool with slow speed stirring.

Example 4(b) - Topical Lotion Composition

A typical composition for delivery as a topical lotion is outlined below: 8-methyl-N-vanillyl-6-noneamide 1.2 g

Sorbitan Monolaurate 1.0 g Polysorbate 20 0.7 g

Cetostearyl Alcohol 2.0 g

Glycerin 7.5 g

Methyl Hydroxybenzoate 0.5 g

Sterilised isotonic saline to about 100.00 ml The methyl hydroxybenzoate and glycerin are dissolved in 70 ml of the isotonic saline at 75°C. The sorbitan monolaurate, polysorbate 20 and cetostearyl alcohol are melted together at 75°C and added to the aqueous solution. The resulting emulsion is homogenised, allowed to cool with continuous stirring and 8-methyl-N-vanillyl-6- noneamide are added as a suspension in the remaining water. The whole suspension is stirred until homogenised.

Example 4(c) - Eye Drop Composition

A typical composition for delivery as an eye drop is outlined below: 8-methyl-N-vanillyl-6-noneamide 0.3 g

Methyl Hydroxybenzoate 0.003 g

Propyl Hydroxybenzoate 0.08 g

Purified isotonic saline to about 100.00 ml. The methyl and propyl hydroxybenzoates are dissolved in 70 ml isotonic saline at

75°C, and the resulting solution is allowed to cool. 8-methyl-N-vanillyl-6-noneamide is then added, and the solution sterilised by filtration through a membrane filter (0.22 μm pore size), and aseptically packed into sterile containers.

Example 4(d) - Ointment Composition A typical composition for delivery as an ointment includes 1.5g of 8-methyl-N- vanillyl-6-noneamide, together with white soft paraffin to 100.0 g, is dispersed to produce a smooth, homogeneous product.

Example 5

8-methyl-N-vanillyl-6-noneamide may also be administered as a composition also comprising a therapeutically effective amount of a local anaesthetic, either alone, or more preferably as a pharmaceutical formulation. The following specific formulations are to be construed as merely illustrative examples of formulations and not as a limitation of the scope of the present invention in any way.

Example 5(a) - Topical Cream Composition A typical composition for delivery as a topical cream is outlined below:

8-methyl-N-vanillyl-6-noneamide 1.0 g

Lidocaine 0.8g

Polawax GP 200 28.0 g

Lanolin Anhydrous 2.50 g White Beeswax 4.8 g

Methyl hydroxybenzoate 0.2 g

Isotonic saline to 100.0 g The polawax, beeswax and lanolin are heated together at 60°C, a solution of methyl hydroxybenzoate is added and homogenisation is achieved using high speed stirring. The temperature is then allowed to fall to 50°C. 8-methyl-N-vanillyl-6-noneamide and lidocaine is then added and dispersed throughout, and the composition is allowed to cool with slow speed stirring.

Example 5(b) - Topical Lotion Composition

Proparacaine 0.8g Sorbitan Monolaurate 1.0 g

Polysorbate 20 0.7 g

Cetostearyl Alcohol 2.0 g

Glycerin 7.5 g

Methyl Hydroxybenzoate 0.5 g Sterilised isotonic saline to about 100.00 ml

The methyl hydroxybenzoate and glycerin are dissolved in 70 ml of the isotonic saline at 75°C. The sorbitan monolaurate, polysorbate 20 and cetostearyl alcohol are melted together at 75°C and added to the aqueous solution. The resulting emulsion is homogenised, allowed to cool with continuous stirring and 8-methyl-N-vanillyl-6- noneamide and proparacaine are added as a suspension in the remaining water. The whole suspension is stirred until homogenised.

Example 5(c) - Eye Drop Composition

A typical composition for delivery as an eye drop is outlined below: 8-methyl-N-vanillyl-6-noneamide 0.3 g Proparacaine 0.8g

Methyl Hydroxybenzoate 0.005 g

Propyl Hydroxybenzoate 0.06 g

Purified isotonic saline to about 100.00 ml.

The methyl and propyl hydroxybenzoates are dissolved in 70 ml isotonic saline at 75°C, and the resulting solution is allowed to cool. 8-methyl-N-vanillyl-6-noneamide and proparacaine are then added, and the solution sterilised by filtration through a membrane filter (0.22 μm pore size), and aseptically packed into sterile containers. The foregoing examples are not intended to limit the scope of the present invention, h particular various equivalents and substitutions will be recognised by those skilled in the art in view of the foregoing disclosure and these are contemplated to be within the scope of the invention. Industrial Applicability

The present invention provides a pharmaceutical composition for the treatment and or prevention of ocular pain and/or inflammatory reactions in the eye of a vertebrate, wherein said composition comprises capsaicin or an analogue thereof, or mixture thereof, and at least one anaesthetic. There is also provided a method for the treatment and/or prevention of ocular pain and/or inflammatory reactions in the eye of a vertebrate, wherein said method comprises administering to said eye a therapeutically effective amount of capsaicin or an analogue thereof or a mixture thereof, wherein prior to the administration of said capsaicin or an analogue thereof or mixture thereof, the eye is pre- treated with a therapeutically effective amount of at least one anaesthetic. References

1. Bennett, E.S., et al, Lens care and patient education, ch. 25 in Bennett, E.S. and Weissman, B.A. eds., Clinical Contact Lens Practice. Philadelphia: Lippincott- Raven (1997)

2. Belmonte, C. et al., Excitation by irritant chemical substances of sensory afferent units in the cat's cornea. J. Physiol (London) 437, 709-725 (1991)

3. Belmonte, C. et al, Measurement of corneal sensitivity to mechanical and chemical stimulation with a CO2 esthesiometer. Invest. Ophihalmol. Vis. Sci. 40, 513-519 (1999)

4. Brady, S J. et al. Pharmacotherapy and osteoarthritis. Baillieres Clin. Rheumatol. 11, 749-768 (1997)

5. Buck, S.H. et al. Characterization of the peptide and sensory neurotoxic effects of capsaicin in the guinea pig. J Neurosci. 3, 2064-2074 (1983)

6. Caterina, M. J. et al. The capsaicin receptor: a heat-activated ion channel in the pain pathway. Nature 389, 816-824 (1997) 7. El-Maghraby, A., et al, Randomised bilateral comparison of excimer laser in situ keratomileusis and photorefractive keratectomy for 2.50 to 8.00 diopters of myopia, Ophthalmology 106, 447-457 (1999) 8. Fields, H. and Levine, , Pain- mechanisms and management, Western Medical J. 141, 347-357 (1984) 9. Liesegang, TJ. Diagnosis and therapy of herpes zoster opthalmicus. Opthalmol. 98, 1216-1229 (1991)

10. Maggi, C.A. Prog. Neurobiol. 45, 1-98 (1995)

11. Nolano M. et al Topical capsaicin in humans: parallel loss of epidermal nerve fibres and pain sensation. Pain 81, 135-145, (1999)

12. Price, D.D. Psychophysical measurement of normal and abnormal pain processing. in: Touch, temperature, and pain in health and disease: mechanisms and assessment. Progress in Pain Research and Management, vol. 3, Boivie, J. et al, eds. IASP Press (1994) 13. Wrigglesworth, et al. Analogues of capsaicin with agonist activity as novel analgesic agents. Structure-activity studies, J. Medical Chem., 39, 4942-4951 (1996)

Table 1: Sensation thresholds for mechanical, chemical, heat and cold stimulation determined at different times after capsaicin application.

Data are mean ± SEM, n = number of explored subjects. * No. of responding subjects/No. of explored subjects. § p<0.05, f ρ<0.01 and J pO.OOl; Student t-test, differences from control.

Claims

1. A pharmaceutical composition for the treatment and/or prevention of ocular pain and/or inflammatory reactions in the eye of a vertebrate, wherein said composition comprises capsaicin or an analogue thereof, or mixture thereof, and at least one anaesthetic.

2. The composition of claim 1, wherein the ocular pain and/or inflammatory reactions in the eye is derived of: ocular and palpebral surgery, eye manipulations and/or fitting of contact lenses.

3. The composition of claim 1, wherein the ocular pain and/or inflammatory reactions in the eye is derived of: pain and/or discomfort accompanying chronic diseases that produce irritation and pain arising from the anterior segment of the eye and conjunctiva.

4. The composition of any one of claims 1-3, wherein the capsaicin or analogue or mixture thereof is formulated as a liquid, gel, cream, suspension or ocular colirium.

5. The composition of any one of claims 1-4, wherein said capsaicin is trans-8-

Methyl-N-vanillyl-6-nonenamide.

6. The composition of any one of claims 1-5, wherein said capsaicin analogue is

Ν-(4-(2-Aminoethoxy)-3-methoxybenzyl)-Ν'-(2-(4-chlorophenyl)ethyl)thiourea and N-

(4-(2-Aminoethoxy)-3-methoxybenzyl)-N'-(4-tert-butylbenzyl)thiourea.

7. The composition of any one of claims 1-6, wherein the composition further comprises a pharmaceutically acceptable carrier, adjuvant and/or diluent.

8. A method for the treatment and/or prevention of ocular pain and/or inflammatory reactions in the eye of a vertebrate in need of said treatment and/or prevention, wherein said method comprises administering to said eye a therapeutically effective amount of capsaicin or an analogue thereof or a mixture thereof, wherein prior to the administration of said capsaicin or an analogue thereof or mixture thereof, the eye is pre-treated with a therapeutically effective amount of at least one anaesthetic.

9. A method for the treatment and or prevention of ocular pain and/or inflammatory reactions in the eye of a vertebrate in need of said treatment and/or prevention, wherein said method comprises administering to said eye a therapeutically effective amount of the composition of any one of claims 1-7.

10. The method of claim 8 or 9, wherein the ocular pain and or inflammatory reactions in the eye is derived of: ocular and palpebral surgery, eye manipulations and/or fitting of contact lenses.

11. The method of claim 8 or 9, wherein the ocular pain and/or inflammatory reactions in the eye is derived of: pain and/or discomfort accompanying chronic diseases that produce irritation and pain arising from the anterior segment of the eye and conjunctiva.

12. The method of claim 8, wherein said anaesthetic and capsaicin or an analogue thereof or a mixture thereof, are sequentially administered to the front of the eye, ocular adnexa or conjunctiva of the vertebrate.

13. The method of claim 9, wherein the composition is administered to the front of the eye, ocular adnexa or conjunctiva of the vertebrate.

14. The method of any one of claims 8-13, wherein the anaesthetic is a local anaesthetic.

15. The method of claim 14, wherein the anaesthetic is selected from the group consisting of: lidocaine, lignocaine, morphine, tetracaine, procaine, bupivacaine, oxybuprocaine, proparacaine, benzocaine, and cocaine.

16. The method of claim 8, wherein said capsaicin or an analogue thereof or a mixture thereof, is applied to the vertebrate eye in the form of a lotion, cream, liposomes or drops.

17. The method of claim 9, wherein said composition is applied to the vertebrate eye in the form of a lotion, cream, liposomes or drops.

18. The method of claim 16 or 17, wherein the composition is applied to the vertebrate eye via a physical applicator.

19. The method of claim 19, wherein the physical applicator is an eye drop device.

20. The method of any one of claims 8-19, wherein said capsaicin is trans-S- Methyl-N-vanillyl-6-nonenamide.

21. The method of any one of claims 8-20, wherein said capsaicin analogue is Ν- (4-(2-Aminoethoxy)-3-methoxybenzyl)-Ν'-(2-(4-chlorophenyl)ethyl)thiourea and N-(4- (2-Aminoethoxy)-3 -methoxybenzyl)-N' -(4-tert-butylbenzyl)thiourea.

22. The method of any one of claims 8-21, wherein the ocular pain and/or inflammatory reactions in the eye follows photorefractive keratectomy

23. The method of any one of claims 8-21, wherein the ocular pain and/or inflammatory reactions in the eye is associated with the adaptation to rigid gas permeable contact lenses.

24. The method of any one of claims 8-23, wherein the treatment and/or prevention of ocular pain and/or inflammatory reactions in the eye lasts up to 20 days.

25. The method of any one of claims 8-23, wherein the treatment and/or prevention of ocular pain and/or inflammatory reactions in the eye lasts about 7 days.

26. The method of any one of claims 8-25, wherein the vertebrate is selected from the group consisting of human, non-human primate, murine, bovine, ovine, equine, caprine, leporine, avian, feline and canine.