MXPA01000447A - Topical compositions comprising an opioid analgesic and an nmda antagonist - Google Patents

Abstract

A topical opioid paradigm was developed to determine analgesic peripheral effects of morphine. Topical morphine as well as peptides such as [D-Ala2,MePhe4,Gly(ol)5]enkephalin (DAMGO) produced a potent, dose-dependent analgesia using the radiant heat tailflick assay. The topical drugs potentiated systemic agents, similar to the previously established synergy between peripheral and central sites of action. Local tolerance was rapidly produced by repeated daily topical exposure to morphine. Topical morphine tolerance was effectively blocked by the N-Methyl-D-Aspartate (NMDA) receptors antagonist MK801 and ketamine given either systemically or topically. NMDA receptor antagonists reversed pre-existing morphine tolerance. The activity of topical NMDA antagonists to block local morphine tolerance suggests that peripheral NMDA receptors mediate topical morphine tolerance. Morphine was cross tolerant to [D-Ala2,MePhe4,Gly(ol)5]enkephalin (DAMGO), but not to morphine-6&bgr;-glucuronide, implying different mechanisms of action. These observations have great importance in the design and use of opioids clinically. Topical pharmaceutical compositions comprising an analgesic that functions through an opiate receptor and an NMDA receptor antagonist for producing analgesia without inducing tolerance are described.

Description

TOPICAL COMPOSITION COMPRISING AN OPIOID ANALGESIC AND AN NMDA ANTAGONIST FIELD OF THE INVENTION The invention is directed to topical pharmaceutical compositions of an N-methyl-D-aspartate receptor antagonist alone or in combination with an analgesic that functions through an opioid receptor for peripheral analgesia and uses of topical pharmaceutical compositions. for the treatment of pain, with or without minimum development of tolerance to the analgesic.

BACKGROUND OF THE INVENTION Morphine is a potent mu opioid receptor agonist with important central sites of action (Reisine and Pasterna, 1996). Peripheral mechanisms have also been reported and their importance is being increasingly appreciated (Stein et al., 1995, Barber and Gottschlich, 1992, Joris et al., 1987, Junien and ettstein, 1992). Peripheral analgesics have a number of potential advantages in the chemical treatment of pain, particularly limitation of side effects such as constipation and sedation which are typically observed with systemic administration. Given locally in the queue, Ref: 126568 Morphine and other opioids are effective analgesics, working either peripherally or synergistically in central sites (Kolesnikov et al., 1996). In many respects, these studies are similar to chemical investigations (Stein, 1993, Dahl et al., 1990, Dalsgaard et al., 1994, Heard et al., 1992, Joris et al., 1987, Khoury et al., 1992; Mays et al, 1987; Raja et al., 1992). Peripheral mechanisms in tolerance to systemic morphine have also been implicated (Kolesnikov et al., 1996). Early studies reported that tolerance to systemic morphine does not alter sensitivity to given morphine either spinally or supraspinally (Roerig et al., 1984). Although we have also found that the remaining unchanged potency for spinal or supraspinal morphine after chronic morphine dosing, a profound reduction in peripheral potency was observed (Kolesnikov et al., 1996).

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to methods and compositions for providing receptor antagonists of N-methyl-D-aspartate (NMDA) administered topically to obtain a more efficient peripheral analgesia using an analgesic that works through an opioid receptor and for the inhibition of tolerance and / or reversal of tolerance to the analgesic. The present invention provides a topical pharmaceutical composition comprising a N-methyl-D-aspartate receptor antagonist alone or in combination with at least one analgesic that functions through an opioid receptor and a pharmaceutically acceptable topical excipient. Another aspect of the invention is a method for providing analgesia to a mammal, comprising the systemic or topical administration of an analgesic that functions through an opioid receptor, analgesic which is administered before, with, or after topical administration to the patient. mammal of a tolerance reducing or inhibiting amount of tolerance of at least one N-methyl-D-aspartate receptor antagonist. Another aspect of the invention is a method for reversing tolerance in a mammal treated with an analgesic that works through an opioid receptor comprising topical administration of an effective amount to reverse the tolerance of at least one NMDA receptor antagonist. The present invention further provides an analgesic kit that reduces tolerance or inhibits pharmaceutical tolerance, comprising: (A) a pharmaceutical or systemic composition comprising at least one analgesic that functions through an opioid receptor; and (B) a topical pharmaceutical composition comprising at least one N-methyl-D-aspartate receptor antagonist that reduces tolerance or inhibits tolerance.

BRIEF DESCRIPTION OF THE FIGURES Figures la and Ib: topical opioid analgesia in the mouse la) Groups of mice received a topical exposure of 2 minutes to morphine (15 mM; n = 20), DAMGO (2 mM; n = 10) or M6G (20 mM; n = 10) and were tested in the rapid tail test. Ib) The dose response curves were generated for each of the compounds applied topically for 1 min, as described in the Methods. Each drug dose had at least 10 mice / group.

Figures 2a and 2b: Effects of topical Mu opioid antagonists 2a) Groups of mice (n> 10) received morphine (15 mM), DAMGO (2 mM) or M6G (20 mM) topically for 1 minute alone or with naloxone (1 mg / kg, sc) injected subcutaneously in the back 20 minutes before the analgesic agonists. Naloxone, a Mu receptor antagonist, significantly reduced the responses for all agonists. 2b) Groups of mice (n> 10) received morphine (15 mM), DAMGO (2 mM) or M6G (20 mM) topically for 1 minute alone or with 3-methoxynaltrexone (3-MeONtx, 0.25 mg / kg, sc ) injected subcutaneously in the back 20 minutes before the agonists. 3-MeONtx significantly decreased the response only for M6G.

Figures 3a and 3b: Interactions between topical and systemic or spinal morphine 3a) Groups of mice (n> 10) received topical morphine (15 mM, 2 min) alone, or with spinal (100 ng, it) or systemic morphine ( 1 mg / kg, sc). The dose of spinal morphine alone had no observable action and the systemic dose produced only a 10% response. At 30 minutes, when the response to the topical drug was only lost, the responses of the combinations were significantly higher. 3b) Left: Groups of mice (n> 10) received topical morphine (15 mM, 2 min) alone, or with spinal morphine (100 ng, i.t.) alone or both together. The test was performed 10 minutes after the administration of the drug. At this point in time, topical morphine alone had a 30% response. The combined dosage was significantly more active than the sum of the two individual routes alone. Right: Groups of mice (n> 10) received topical morphine (15 mM) alone, or with systemic morphine (1 mg / kg s.c.) alone or both together. The test was performed 30 minutes after the administration of the drug. At this point in time, topical morphine alone did not have an observable response. The combined dosage was significantly greater than the sum of the two individual routes alone.

Figure 4: Tolerance to systemic and topical morphine Groups of mice (n> 10) received morphine systemically (5 mg / kg, s.c.) or topically (15 mM, 1 min).

DMSO alone had no observable effect on days 1, 2 or 3.

On day 3, the response in the systemic group was significantly greater than in the topical group.

Figure 5: Cross tolerance between morphine, and DAMGO and M6G Groups of mice (n> 10) received morphine (5 mg / kg, s.c.) or saline daily for 5 days. On the sixth day, the mice were tested after local exposure (1 min) to morphine (15 mM), M6G (20 mM) or DAMGO (2 mM). The response to morphine and DAMGO after chronic treatment with morphine decreased significantly (p < 0.01). There was no change in the response to M6G.

Figures 6a, 6b and 6c: Effect of MK801 on tolerance to topical morphine. 6a) Groups of mice (n> 10) received topical morphine (15 mM, 1 min) alone or with MK801 given either topically (3 mM), systemically (0.1 mg / kg, sc) or intrathecally (1 μg, it ). After three days the response to morphine alone was lost (p <0.01), as was the response to morphine with the intrathecal MK801 (p <0.01). The combination of morphine with systemic or topical MK801 remained essentially unchanged for 5 days. 6b) Groups of mice (n> 10) received topical morphine (15 mM, 1 min) alone, topical MK801 alone (3 mM) or topical morphine (15 mM) with topical MK801 at the indicated concentration (0.15, 0.3 or 3). mM). After three days, the response to morphine alone was lost (p <0.01). The two higher doses of MK801 prevented the loss of response (p <0.01) while the lower doses had an intermediate response. 6c) Groups of mice (n _> 10) received topical morphine (15 mM, 1 min) alone for 3 days. Starting on the fourth day, they received topical morphine with topical MK801 at either 0.3 or 3 mM. Co-administration of MK801 with topical morphine reversed the previously established tolerance (p <0.01).

Figures 7a and b: Effect of ketamine on tolerance to topical morphine 7a: Groups of mice (n = 20) were treated topically once a day for 3 days with morphine (15 M) alone (closed circles) or with morphine with ketamine at 3.6 mM (triangles) or 36mm (open circles). Ketamine alone (36 mM) did not produce significant analgesia in this model.

After three days, the response to morphine alone was lost (p <0.001). The lowest dose of ketamine (3.6 mM) significantly decreased the loss of the analgesic response of morphine after three days (p <0.05). The highest dose of ketamine (36 mM) prevented tolerance up to six days (p <0.0001) 7b. Groups of mice (n = 20) received topical morphine (15 mM) alone (closed circles) for two days. Starting on day 3, the two groups of mice received daily doses of morphine together-with ketamine at 3.6 (triangles) or 36 mM (squares) until day 6. The highest dose of ketamine (36 mM) completely restored the analgesia of morphine (p < 0.0001) DETAILED DESCRIPTION OF THE INVENTION The present invention provides a topical pharmaceutical composition comprising at least one N-methyl-D-aspartate (NMDA) receptor antagonist alone or in combination with at least one analgesic that functions through an opioid receptor and a pharmaceutically acceptable topical excipient. Antagonists of the N-methyl-D-aspartate receptor for use in the present invention include but are not limited to morphinan such as dextromethorphan ((+) - 3-hydroxy-N-methylmorphinan) and dextrofan ((+) - 3 -hydroxy-N-methylmorphinan), MK-801 (acid maleate of ((5R, 10S) - (+) - 5-methyl-10, 11-dihydro-5H-dibenzo [a, d] cyclohapten-5, 10- imine), ketamine (2- (2-chlorophenyl) -2- (methylamino) ciciohexanone), pyroloquinoline quinone and cis-4- (phosphonomethyl) -2-piperidine carboxylic acid, memantine (3,5-dimethyl-9- hydrochloride) adamantanamine), mixtures thereof, and pharmaceutically acceptable salts thereof and the like. "Except for dextromethorphan, many current NMDA receptor antagonists have not been suitable for systemic clinical use because of the profound psychomimetic side effects such as NMDA receptor antagonists. however, they can be used in the present invention in topical formulations.The topical use of these antagonists of the NMDA receptor allows the interference and attenuation of the development of tolerance to analgesics without producing side effects limiting. NMDA receptor antagonists that can be used in topical formulations include but are not limited to MK 801, dextromethorphan, ketamine, memantine, dextrofan, mixtures thereof and pharmaceutically acceptable salts thereof, pyroloquinolin quinone, cis-4- (phosphonomethyl) acid. ) -2-piperidine carboxylic acid, their mixtures and pharmaceutically acceptable salts thereof, and the like. Analgesics that can be used in the present invention are those that provide analgesia through the activation of at least one type of opioid receptor. Opioid receptors that can be activated by the analgesic component of the present invention include but are not limited to any or combinations of opiate receptors delta (d), kappa opioid receptors (K) and Mu opioid receptors. Analgesics include but are not limited to opioids, opioid derivatives, and synthetic opioids, endogenous or opioid peptides. synthetics such as the enkephalins, endorphins and their pharmaceutically acceptable salts. Specific examples include ethylmorphine, hydromorphone, morphine, codeine, oxymorphine, [D-Ala2, MePhe4, Glycol) J] encephalomyelitis (DAMGO), propoxyphene, buprenmorphine, oxycodone, hydromorphone, hydromorphine, phenanthyl, sufentanil, pentazocine, nalbuphine, nalorphine, heroin, levorphanol, levalorfan, methadone, meperidine, cocaine, dihydrocodeine, hydrocodone, nalmefan, naloxone, naltrexone, butorphanol and the pharmaceutically acceptable salts and the like. Optionally, the topical pharmaceutical composition of the present invention may further comprise a local anesthetic, including, but not limited to lidocaine, bupivacaine, mepivacaine ropivacaine, tetracaine, benzocaine, and the like. As used herein, a mammal that can benefit from the methods of treatment of the present invention is any warm-blooded animal in need of pain management. Mammals include but are not limited to humans, primates, dogs, cats, rodents, horses, cattle, sheep and the like. The analgesic is provided to a mammal in need of pain relief. The pain can be acute or chronic pain. Diseases or conditions that may require analgesia include but are not limited to pain associated with trauma, amputation, neuropathy, fibrimyalgia, burns, abrasions, infections, lacerations, incisions, and the like. This invention provides the attenuation or prevention of the development of tolerance associated with the administration of narcotic analgesics. Consequently, NMDA receptor antagonists can be administered in amounts which are effective in attenuating or preventing the development of tolerance. As used herein, the term "dose" to prevent tolerance, inhibit tolerance, or revert tolerance is an amount of an NMDA receptor antagonist effective to maintain and / or restore, or at least partially restore, the analgesic effect of the narcotic analgesic. . In a method for providing periphery analgesia to a mammal, a dose to attenuate or prevent tolerance of at least one NMDA receptor antagonist is administered topically before, concurrently or after topical administration of at least one analgesic that works through a receptor. opiate. In one embodiment of the method for providing analgesia to a mammal, a dose of NMDA receptor antagonist, ketamine which attenuates or inhibits tolerance, is administered topically, concurrently or after. topical administration of the opioid analgesic, morphine.

In another embodiment of the method for providing analgesia to a mammal, a dose that inhibits tolerance or reverses the tolerance of the NMDA receptor antagonist, dextromethorphan, is administered topically before, concurrently or after topical administration of the opioid analgesic, morphine. The administration of a topical pharmaceutical composition of the invention may be in the form of a single unit dose comprising the NMDA receptor antagonist alone or in combination with the analgesic in a topical formulation in effective amounts. The concentration of the topical NMDA receptor antagonist in the pharmaceutical composition is in the range of about 0.1% to about 5% by weight in admixture but can vary in amounts depending on the particular antagonist used and the particular analgesic that is being administered to the mammal. The concentration of the topical NMDA receptor antagonist provides an effect that decreases the dose over the concentration of the analgesic necessary to provide effective analgesia. For example, an analgesic concentration, when used in combination with a topical NMDA receptor antagonist in a range of about 1.0 to about 10% by weight for topical administration of the analgesic, in a range of about 0.1 to about 0.2 mg / kg of body weight for the systemic administration of the analgesic in the range of approximately 1-5 mg for intrathecal administration of the analgesic. A particular dose of the topical composition may be provided for example, 2-3 times per day, or any period sufficient to prevent, inhibit or reverse tolerance in the mammal receiving an analgesic that works through an opioid receptor.

Topical pharmaceutical compositions can be formulated as an aqueous solution, lotion, gel, cream, ointment, adhesive film and the like, with pharmaceutically acceptable excipients such as aloe vera (aloe), propylene glycol, DMSO, lecithin base and the like. DMS, as used in the present invention, does not provide the systemic adsorption of the therapeutic agent. A carrier in the form of a gel may comprise one or more of the following - petrolatum, lanolin, polyethylene glycols, beeswax, mineral oil, diluents, such as water and alcohol, and emulsifiers and stabilizers. Aqueous suspensions may contain the composition in admixture with pharmaceutically acceptable excipients such as suspending agents, for example, sodium carboxymethylcellulose, methyl cellulose, hydroxypropylmethylcellulose, sodium alginate, polyvinylpyrrolidone, gum tragacanth and acacia gum; dispersing or wetting agents such as natural phosphatides, for example, lecithin or condensation products of an alkylene oxide with fatty acids, for example polyoxyethylene stearate or condensation products of ethylene oxide with long chain aliphatic alcohols, for example, heptadecaethyleneoxycetanol , or condensation products of ethylene oxide with partial esters derived from fatty acids and hexitol, for example, polyoxyethylene sorbitol monoleate or condensation products of ethylene oxide with partial esters derived from fatty acids and hexitol anhydrides, for example, monooleate of polyoxyethylene sorbitan. Such aqueous suspensions may also contain one or more preservatives, for example ethyl or n-propyl-p-hydroxybenzoate. Dispersible powders and granules suitable for the preparation of an aqueous suspension by the addition of water provide the composition in admixture with a dispersing or wetting agent, a dispersing agent and one or more preservatives. The dispersing or wetting agents and suitable suspending agents are exemplified by those already mentioned above. The composition of this invention or any of its main active ingredients can be provided in sustained release dosage formulations that are known in the art. A topical formulation of the present invention produces a therapeutic effect on peripheral opiate receptors and is not required to release the active ingredients in the topical formulation to the central opiate receptors (brain and spinal cord). The topical formulations of the present invention provide for the local release of the active ingredients and are not required to provide the systemic release of the active ingredients in the formulation in the treated mammals. Topical administration of the pharmaceutical composition can be achieved by the application of a solution, gel, lotion, ointment, cream or other vehicle used topically to release therapeutic agents to a local site. One of the means of application is by spraying the composition on the area to be treated. In another embodiment, a patch that provides a sustained release of topical formulation to administer the topical therapeutic agent may also be used. The patch can be one of the reservoir or porous membrane type or a solid matrix as is well known in the art. The active agents can be in a plurality of microcapsules distributed through the permeable adhesive layer. In another embodiment of the method for providing analgesia to a mammal with preexisting tolerance to an analgesic, a dose that reverses the tolerance of at least one NMDA receptor antagonist concurrently or after topical or systemic administration of at least one analgesic is administered topically. that works through an opioid receptor. The pharmaceutical composition of the NMDA receptor antagonist for topical administration may also be provided in the form of a kit, together with at least one topical or systemic pharmaceutical composition comprising an analgesic that functions through an opioid receptor. The present invention also encompasses a method for providing analgesia to a mammal, comprising topically administering at least one analgesic that functions through an opioid receptor prior to, concurrently, or following systemic or intrathecal administration of at least one analgesic. . The combination of topical administration with systemic or intrathecal administration of an analgesic provides effective and therapeutic analgesia at low doses of the topical analgesic and low doses of systemic or intrathecal analgesic with the concomitant decrease in the side effects of the analgesic. The doses used in combination therapy are doses that lower the dose required to achieve a therapeutic level of analgesia using any analgesic, alone. The concentration of the topical analgesic in a pharmaceutical composition for use in the combined analgesic therapy ranges from about 1 to about 10% by weight. The concentration of the analgesic in a pharmaceutical composition for use in the combined analgesic therapy is in a range such that it provides about 0.1 to about 0.2 mg / kg of body weight. In the case of intrathecal administration of the analgesic, in combination with a topical analgesic, the concentration of the intrathecal analgesic is in the range of about 1 to about 5 mg. The therapy can be supplemented by administration of a dose that attenuates tolerance or prevents tolerance of at least one topical NMDA receptor antagonist. The topical NMDA receptor antagonist may be provided in a concentration range of about 0.1% to about 5% by weight of the formulation. In one embodiment of a method for providing analgesia to a mammal, topical morphine is administered before, concurrently or after systemic or intrathecal administration of morphine. The above description of the specific modalities will fully reveal the general nature of the invention that others, applying the current understanding, can easily modify and / or adapt for various applications such as specific modalities without departing from the generic concept, and therefore it is intended that such adaptations and modifications are within the meaning and scope of equivalents of the described modalities. All references and patents referred to are incorporated herein by reference.

Example 1 Materials and Methods Male Crl: CD1 (ICR) BR mice (25-30 g, Charles River Breeding Laboratories, Bloomington, MA) were maintained in a 12 h light / dark cycle with feed and water available ad libi tum. The mice were housed in groups of five until tested. The [125I] NaI (1680 Ci / mmol) was purchased from New England Nuclear (Boston, MA). Morphine, morphine-6β-glucuronide (M6G) and [D-Ala2, MePhe4, Gly (ol) 5] enkephalin (DAMGO) were generously provided by the Research Technologies Division of the National Institute of Drug Abuse (Rockville, MD ). The MK801 was purchased from Research Biochemicals, Inc. (Natick, MA). The systemic drugs were given subcutaneously (s.c.) in the middle capsular region of the back. Intracerebroventricular (i.c.v.) and intrathecal injections were performed under mild halothane anesthesia 30 and 15 minutes before the test, respectively, as reported previously (Kolesnikov et al., 1996). The injections i.c.v. 2 mm caudal and 2 mm lateral to the bregma were administered at a depth of 3 mm, while intrathecal injections were made by lumbar puncture. The drugs were given topically on the glue by immersion of the glue in dimethylsulfoxide (DMSO) solutions containing the indicated drugs. The distal portion of the tail (3 cm) was immersed in DMSO solution for 1 minute. The latencies were then determined by tapping the tail on the region of the tail immersed in the drug, unless otherwise stated. To ensure a local effect, the test was also performed with a more proximal segment of the tail not exposed to the drug solution. The analgesia was evaluated with the test of hitting the tail, as previously reported (Kolesnikov et al., 1996). The tail was exposed to a focused beam of light and the latency of the exposure was determined. The latencies of the baseline fluctuated from 2.5 to 3.5 seconds. A latency of 10 seconds maximum cut was used to minimize tissue damage in analgesic animals. The test was carried out 30 minutes after the systemic administration, 15 minutes after the i.c.v. injections. or i.t. or immediately after finishing topical administration in the queue. Antinociception, or analgesia, was defined quantitatively as a latency by tapping the tail for an individual mouse which used at least twice its latency in the baseline. The group comparisons were made using Fisher's exact test. The ED50 values were determined using the Bliss program, as previously reported (Pick et al., 1993). To ensure local action, in all studies we examined a region of the tail which was immersed in DMSO as well as a more proximal segment that was not exposed. The latencies when striking the tail of the unexposed portion of the tail were similar to the latencies of the baseline. DMSO itself did not have activity in this model. The tail test regions exposed and not exposed to DMSO did not reveal a significant antinociceptive effect at any location. [125I] Morphine and [125I] DAMGO were synthesized at room temperature using the chloramine T method with equimolar amounts of [125I] NaI and either morphine or DAMGO. The reaction was terminated with sodium metabisulfite after 1 minute and the radioactively labeled opioid separated from the unreacted N125I by a C18 reverse phase SepPak (Chien et al., 1997). The radiolabelled compounds were not further separated from the non-iodinated precursors.

Example 2 Analgesia with morphine and topical DAMGO Previous studies in our group demonstrated a potent local analgesic activity of morphine administered subcutaneously in the tail (Kolesnikov et al., 1996). Morphine was also a potent analgesic when it was applied topically. The analgesic response to a morphine solution (7.5 mM) increased progressively over time, going from only 25% after 30 seconds to 50% in 1 minute and to 80% after 2 minutes (data not shown). The appearance of the response was very rapid. The analgesia was detectable within 1 minute after the removal of the tail of the opioid solution, the shortest time tested (Figure la). However, the duration of response to morphine was relatively short, typically lasting less than 30 minutes. Using a fixed exposure time, the effect produced by morphine depended on the dose (Figure Ib).; Table 1). Similar results were observed with DMSO opioid peptide DMSO solutions, which was 5 times more potent (Figure Ib, Table 1).

Table 1: Analgesic activity of topical opioids in CD-1 mice The ED50 values of the analgesic with 95% confidence limits were determined using at least three doses of the drug in groups of mice (n = 10-20 / dose) in the tapping test. All drugs were administered topically for 1 minute, as described in the Methods. The ratio of M6G and DAMGO was determined against morphine. In addition to its greater power, the DAMGO also had a longer duration of action, lasting almost an hour (Figure la). Like morphine, the DAMGO peak actions were observed immediately after the removal of the DMSO solution. These analgesic responses were easily reversed by systemic naloxone (1 mg / kg s.c.), confirming the opioid selectivity of the response (Fig. 2a). In addition, no analgesic response was observed with these agents in the proximal portions of the tail not exposed to opioid solutions. To further confirm the selectivity of the method, we observed the distribution of radioactivity after immersion in a solution containing [125I] morphine or the [125I] DAMGO (Table 2). The region of the tail exposed to the solution had high levels of radioactivity. A nearer portion of the tail that was not exposed directly to the solution had radioactivity levels < 1% of those in the distal portion of the tail immersed in the solution. In addition, no detectable levels of radioactivity were observed in the tail, brain or spinal cord.

Table 2: Distribution of [125I] DAMGO after topical administration The distal part of the tail (4-4.5 cm) was immersed in morphine or DAMGO labeled with [1251] (100 μCi / ml) in DMSO and exposed for 3 minutes. The brain, spinal cord, blood samples as well as segments of the exposed and unexposed portions of the tail were obtained within 5 minutes of exposure, weighed and counted directly on a Packard 5500 Gamma Spirometer. The unexposed tail was less than 1 cm from the exposed region. The radioactivity was expressed in cpm per gram of tissue (cpm / g). The results are the means ± s.e.m. of three animals for each radioactively labeled drug.

Example 3 Analgesia of topical morphin-6β-glucuronide Morfin-6β-glucuronide (M6G) administered locally by subcutaneous injection into the tail was analgesic, but had a ceiling effect of 30% at doses of 10 or 30 μg (not shown). data). In the topical paradigm, the M6G with a complete analgesic response with a peak effect immediately after the removal of the solution (Figure la) and a potency similar to that of morphine (Figure Ib; Table 1) . As with morphine, the proximal tail segments did not present analgesia and the response to M6G was rapidly reversed by systemic naloxone (Figure 2a). The duration of action of M6G after topical administration was similar to that of DAMGO and more prolonged than that of morphine (Figure la). The selective 3-methoxy naltrexone antagonist (3MeONtx) (Brown et al., 1997) of the M6G also significantly decreased the response to M6G (Figure 2b). in contrast, the same dose of 3MeONtx was inactive against the analgesic actions of morphine or DAMGO (Figure 2b). In addition to supporting the 3MeONtx selectivity for M6G receptors, these receptors strongly supported the presence of functional peripheral M6G receptors.

Example 4 Peripheral / central synergy The previous work of our laboratory has suggested a powerful synergy between the peripheral and central morphine systems. We also examined those interactions after topical administration. Typically, the actions of morphine dissipated rapidly, falling from 80% in one minute to only 30% in 10 minutes. No analgesia was observed at 30 minutes. Minimally active doses of intrathecal or subcutaneous morphine potential to the response of topical morphine (Figure 3). This is more dramatic to team points to the signal in 30 minutes point at which the topical response alone was completely lost. In those longer team points, the analgesic responses of the combinations were significantly greater than their additive effects (Figure 3b).

Next, we observed the effects of a fixed dose of topical morphine on the values of the ED50 and the spinal and systemic morphine (Table 3).

Table 3: Effects of topical morphine on analgesia in systemic and spinal morphine The ED50 values and the 95% confidence limits were determined for systemically given morphine alone or in conjunction with a fixed dose of topical morphine (15mM). The test was performed 30 minutes after the treatments, at which point there were no observable effects of topical morphine alone. The ED50 values and the 95% confidence limits were determined for morphine given intrathecally alone and with a fixed dose of topical morphine (15 mM). The test was performed 15 minutes after the treatment, at which point the topical morphine had only a limited response (15%). Topical morphine potentiated the analgesic potency of systemic morphine almost 7 times, although it did not have activity alone at the point in time examined (30 minutes). Topical morphine also increased the potency of intrathecal morphine by almost 12-fold. In this way, these results support the first suggestions for potentiation between the peripheral and central morphine analgesic systems.

Example 5 Tolerance to peripheral morphine Peripheral systems are important in the production of tolerance after. systemic administration of morphine (Kolesnikov et al., 1996). The tail immersion method allows repeated local administration of drugs without tissue damage, facilitating the study of tolerance to peripheral morphine. Topical daily morphine (15 mM) produced a deep tolerance on the third day (Figure 4), deviating the value of the DE5o from morphine more than 9 times (Table 4). Topical tolerance developed rapidly and to a lesser degree than that observed with the systemic drug daily, where 5 days of treatment only diverted the response to the dose of morphine by approximately 2-fold.

Table 4: Tolerance to systemic and topical morphine The ED50 values after topical or systemic administration were determined in candid mice or in groups of mice that had received morphine chronically. The ED50 values and the 95% confidence limits were determined using at least three doses of drug (n = 10-20 / dose). In the systemic group, the mice received morphine (5 mg / kg, sc) daily for 4 days before the test while the topical group was treated with a morphine solution (15 mM) daily for two days and the value of the DE50 was determined on the third day. At least three doses of morphine were used to calculate ED50 values.

Mice given systemic morphine showed significant tolerance to topical morphine as well as mu DAMGO peptide (Figure 5). However, the analgesic activity of topical M6G in these mice remained unchanged, confirming the absence of the cross-tolerance reported previously (Rossi et al., 1996).

Example 6 Blockade of tolerance to peripheral morphine by NMDA antagonists, or MK 801 The NMDA / nitric oxide cascade plays an important role in the production of morphine tolerance (Kolesnikov et al., 1993). Blocking this system results in the development of tolerance of morphine without interfering with analgesia. The NMDA antagonist MK 801 given systemically also prevented the development of tolerance to topical morphine (Figure 6a). Topical MK 801 also blocked tolerance to morphine as effectively as the systemic drug (Figure 6a), but intrathecal MK 801 was not effective. The actions of the topical MK 801 were dose dependent, with 0.3 mM effectively blocking tolerance (Figure 6b).

In addition, the topical MK801 can revert the preset tolerance (Figure 6c). After treating the mice with topical morphine only for three days the analgesic response was eliminated. The addition of MK801 to the treatment regimen restored the analgesic sensitivity during the following two days despite the continuous administration of morphine. The highest doses of MK801 were significantly more effective than the lowest. The low rate of reversion without effect after the first dose argued strongly against a simple potentiation of morphine potency.

EXAMPLE 7 Blockade of tolerance to peripheral morphine by the NMDA antagonist, ketamine Daily topical morphine (15 mM) led to tolerance with complete loss of analgesia on the third day (Figure 7A and B). The NMDA receptor antagonist ketamine given systemically prevented the development of tolerance to topical morphine, but ketamine was not effective (data not shown). Topical ketamine was coadministered with morphine blocked tolerance as effectively as the systemic drug in a dose-dependent manner (Figure 7A). The lower dose (3.6 mM) delayed the onset of tolerance, but the higher dose (36 mM) effectively blocked tolerance. Ketamine alone had no appreciable effect in this trial. Topical ketamine also reversed the pre-established tolerance (Figure 7B). After treating the mice with a fixed concentration of topical morphine alone for 3 days the mice did not show analgesia. Ketamine added to the treatment regimen restored analgesic sensitivity over the following 3 days despite continuous administration of morphine. The ability of topical ketamine to prevent and / or reverse tolerance to morphine implies a peripheral mechanism of action and is similar to the previous experiment with dizocilpine (MK-801). Mechanistically, these observations are consistent with the possibility that peripheral tolerance is mediated through peripheral NMDA receptors, possibly on the same ganglionic neurons of the dorsal root that contains the opioid receptors.

Discussion Peripheral opioid actions are becoming increasingly important in our understanding of Opioid actions, as demonstrated by the role of peripheral and central synergy in the actions of systemic morphine (Kolesnikov et al., 1996). In addition, peripheral sites of action play a major role in the development of tolerance to systemic drugs. The exploration of peripheral mechanisms is not simple. The first studies used local injections in the tail to examine the peripheral mechanisms. Although useful, this method has a number of disadvantages, particularly when observed at repeated doses. In an effort to avoid this problem, we developed a topical method which is generally applicable to both alkaloids and peptides. The technique of immersing the tail has numerous advantages. The first is the ability to repeatedly treat mice without damage to tissue secondary to injections. The paradigm was selective for local mechanisms. Proof of the proximal regions of the tail failed to "reveal any analgesic response, confirming the distribution studies with 125I-opioid which documented the location of the radioactive label only in the regions submerged in the drug solution and the absence of any detectable uptake in the blood or central nervous system Equally important, DMSO alone had no effect in the tapping tests Presumably, the activity of this method was not limited to DMSO and other solvents or creams could be used We do not anticipate that peptide topical solutions are active, but a number of different mu and delta peptides are effective in this paradigm Clearly, topical methods open new clinical possibilities for those peptides which are not systemically very effective. This way, the topical method provides a useful method for the examination of op peripheral ioids and as a therapeutic agent in pain management. Peripherally, all. Proven opioids were effective analgesics. Of the three, DAMGO was the most effective. The similar potencies of morphine and M6G peripherally contrast with their central actions, where M6G is approximately 100 times more active than morphine. In all cases, the proximal segments of the tail that were not exposed to the opioid solution were not analgesic, confirming the peripheral site of action of the submerged sites in the opioid solution. The responses were easily antagonized by naloxone. Centrally, 3-MeONtx selectively reverses analgesia of M6G without interfering with morphine analgesia, consistent with the different mechanisms of receptor action (Brown et al., 1997). 3MeONtx also reversed the analgesia of the peripheral M6G without affecting the actions of DAMGO or morphine. Thus, the peripheral analgesia of the M6G showed the same antagonistic selectivity observed centrally.

Previous studies have documented synergy between the actions of peripheral and central morphine. Current studies confirmed those early observations. t'3 combination of topical morphine with systemically or spinally given formamide revealed a remarkable enhancement of the response beyond that expected for simple additive interactions. Thus, if topical opioids can be used clinically, the results would suggest that they would be more effective in combination with systemic dosing. By lowering the necessary doses of the systemic drug, topical opioids can greatly reduce the side effects currently associated with opioid analgesics. Chronic dosing with treatment with systemic morphine leads to tolerance. Locating the site of tolerance to morphine has been difficult. Mice tolerant to systemic morphine show normal sensitivities to given spinal or supraspinal morphine (Roering et al., 1984), but not peripherally (Kolesnikov et al., 1996). In fact, the 19-fold deviation in the dose-response curves of local morphine far exceeded the deviation after systemic administration. Our current studies support a role for peripheral sites in tolerance to morphine. Chronic topical morphine produced tolerance very quickly, decreasing the response to undetectable levels for three days corresponding to a 9-fold deviation in the dose-response curve. Chronic dosing with DMSO had no effect. The rate of development of tolerance to the equianalgesic dose of the systemic drug decreased to a lesser degree, deviating the dose-response curve over 2 times after 5 days. Peripheral morphine tolerant mice showed cross tolerance to DAMGO, but not to M6G. This lack of cross-tolerance is consistent with the selective reversal of M6G analgesia by 3-MeONtx and is consistent with the mechanism of action of single receptor M6G. Antagonists of the N-methyl-D-aspartate receptor (MDA) or inhibitors of nitric oxide synthase (NOS) prevents the production of tolerance to morphine (Trujillo and Akil, 1994, Gutstein and Trujillo, 1993, Bén-Eliyahu et al., 1992, Kolesnikov et al., 1993) . In view of the importance of peripheral opioid mechanisms in the tolerance of these paradigms, we observed the role of peripheral NMDA antagonists. Tolerance to topical morphine was effectively blocked by systemically or topically given MK801, but not spinally. It would be expected that the systemic MK801 would have access through the animal including the peripheral sites, while the intrathecal drug would be restricted to central sites. Similarly, topical ketamine prevented and / or reversed tolerance to morphine. Thus, only treatments with access to peripheral sites were active in this model, implying that peripheral NMDA receptors are responsible for mediating tolerance to topical morphine. Recent evidence supports the presence of excitatory amino acid receptors (EAA) on peripheral skin axons (Carlton et al., 1995, Davidson et al., 1997, Zhou et al., 1996). Additional studies are necessary to verify the site of action. However, the activity of topical NMDA antagonists opens many clinical possibilities in the administration of pain. Many of the current NMDA receptor antagonists are not suitable for clinical use due to profound psychomimetic side effects. Restricting its use to topical formulations may provide a way to use its ability to interfere with the development of tolerance without producing side-limiting effects. Peripheral opioids clearly have important roles in analgesia and tolerance. The ability of topical opioids to produce analgesia only and potentiate systemic drugs offers a new method that can prove clinical utility. The activity of topical peptides further improves this method since it opens the way for many highly selective agents to act through non-mu opioid receptor mechanisms. Finally, the ability to block topical tolerance with peripherally acting NMDA antagonists is another exciting advance in the clinical management of pain.

References Barber, A and Gottschlich, R (1992) Opioid agonists and antagonists: an evaluation of their actions in inflanimation. Med Res Reviews 12: 525-562. Ben-Eliyahu, S, Marek, P, Vaccarino, AL, Mogil, JS, Stemberg, WF and Liebeskind, JC (1992) The NMDA receptor antagonist MK-801 prevents long-lasting non-associative morphine tolerance in the rat. Brain Res 575: 304-308. Brown, GP, Yang, K, King, MA, Rossi, OC, Leventhal, L, Chang, A and Pasternak, GW (1997) 3-Methoxynaltrexone, a selective heroin / morphine-6 ß-glucuronide antagonist. FEBS Lett 412: 35-38. Carlton, SM, Hargett, GL and Coggeshall, RE (1995) Localization and activation of glutamate receptors in unmyelinated axons of rat glabrous skin. Neurosci Let t 197: 25-28. Chien, C-C, Carroll, Fl, Brown, GP, Pan, Y-X, Bowen, W and Pasternak, GW (1997) Synthesis and characterization of [125I] 3 '(-) -iodopentazocine, a selective to receptor ligand. Eur J Pharmacol 321: 361-368.

Dahl, MR, Dasta, JF, Zuelzer, W and McSweeney, TD (1990) Lidocaine local anesthesia for arthroscopic knee surgery. Anesth Analg 71: 670-674. Dalsgaard, J, Felsby, S, Juelsgaard, P and Froekjaer, J (1994) Low-dose infra-articular morphine analgesia in day case knee arthroscopy: A randomized double-blinded prospective study. Pain 56: 151-154. Davidson, EM, Coggeshall, RE and Carlton, SM (1997) Peripheral NMDA and non-NMDA glutamate receptors contribute to nociceptive behaviors in the rat formalin test. Neuroreporr 8: 941-946. Gutstein, HB and Trujillo, KA (1993) MK-801 inhibits the development of morphine tolerance at spinal sites. Brain Res 626: 332-334. Heard, SO, Edwards, T, Ferrari, D, • Hanna, D, Wong, PD, Liland, A and Willock, MM (1992) Analgesic effect of intraarticular bupivacaine or morphine after arthroscopic knee surgery: a randomized, prospective, double-blind study. Anest Analg 74: 822-826. Joris, JL, Dubner, R and Hargreaves, KM (1987) Opioid analgesia at peripheral sites: a target for opioids released during stress and inflammation? Anesth Analg 66: 1277-1281.

Junien, JL and Wenstein, JO (1992) Role of opioids in analgesia. Life Sci 51: 2009-2018. Khoury, GF, Chen, ACN, Garland, DE and Stein, C (1992) Intraarticular morphine, bupivacaine, and morphine / bupivacaine for pain control after knee videoarthroscopy. Anesthesiology 77: 263-266. Kolesnikov, YA, Jain, S, Wilson, R and Pasternak, GW (1996) Peripheral morphine analgesia: Synergy with central sites and a target of morphine tolerance. J Pharmacol Exp Ther 279: 502-506. Kolesnikov, YA, Pick, CG, Ciszewska, G and Pasternak, GW (1993) Blockade of tolerance to morphine but not to kappa opioids by a nitric oxide synthase inhibitor. Proc Na tl Acad Sci USA 90: 5162-5166. Mays, KS, Lipman, JJ and Schnapp, 'M (1987) Local analgesia without anesthesia using perineural morphine injections. Anesth Analg 66: 417-420. Pick, CG, Nejat, R and Pasternak, GW (1993) Independent expression of two pharmacologically distinct supraspinal mu analgesic systems in genetically different mouse strains. J Pharmacol Exp Ther 2265: 166-171. Raja, SN, Dickstein, RE and Johnson, CA (1992) Comparison of postoperative analgesic effects of intraarticular bupivacaine and morphine following arthroscopic knee surgery. Anesthesiology 77: 1143-1147. Reisine, T and Pasternak, GW (1996) Opioid analgesics and antagonists. In Goodman & Gilman's: The Pharmacological Basis of Therapeutics, ed. by JG Hardman and LE Limbird, PP. 521-556, McGraw-Hill. Roerig, SC, O'Brien, SM, Fujimoto, JA and Wilcox, GL (1984) Tolerance to morphine analgesia: increased multiplicative interaction between spinal and »supraspinal sites. Brain Res 308: 360-363. Rossi, GC, Brown, OP, Levental, L, Yang, K and Pasternak, GW (1996) Novel receptor mechanisms for heroin and morphine-6β-glucuronide analgesia. Neurosci Lett 216: 1-4. Stein, C (1993) Peripheral mechanisms of opioid analgesia. Anesth Analg 76: 182-191. Stein, C, Scháfer, M and Hassan, AHS (1995) Peripheral opioid receptors. Ann Med 27: 219-221. Trujillo, KA and Akil, H (1994) Inhibition of opiate tolerance by non-competitive N-methyl-D-aspartate receptor antagonists. Brain Res 633: 178-188. Zhou, S, Bonasera, L and Carlton, SM (1996) Peripheral administration of NMDA, AMPA or KA results in pain behaviors in rats. Neuroreport 7: 895-900.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (18)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property. A topical pharmaceutical composition characterized in that it comprises at least one N-methyl-D-aspartate (NMDA) receptor antagonist and at least one analgesic that functions through an opiate receptor and a pharmaceutically acceptable topical excipient.
2. 2. The topical pharmaceutical composition according to claim 1, characterized in that it comprises at least one analgesic and wherein the analgesic is selected from the group consisting of an opioid, an opiate derivative, an opioid, encephalins, endorphins and synthetic opioid peptides.
3. 3. The topical pharmaceutical composition according to claim 2, characterized in that the opioid is selected from the group consisting of ethylmorphine, hydromorphine, morphine, oxymorphone, codeine, levorphanol, oxycodone, pentazocine, propoxyphene, fentanyl, sufentanil, lofentanil, morphine. 6-glucuronide and buprenorphine.
4. 4. The topical pharmaceutical composition according to claim 2, characterized in that the enkephalin is selected from the group consisting of [D-Ala2, MePhe4, Gly (ol) 5] enkephalin, and endomorphins.
5. 5. The topical pharmaceutical composition according to claim 1, characterized in that the analgesic is morphine.
6. 6. The topical pharmaceutical composition according to claim 1, characterized in that the NMDA receptor antagonist is selected from the group consisting of dextramethorphan, dextrofan, ketamine, pyroloquinoline quinone, cis-4- (phosphonomethyl) -2-piperidine acid carboxylic acid, MK801, memantine, and mixtures thereof and pharmaceutically acceptable salts thereof.
7. 7. The topical pharmaceutical composition according to claim 1, characterized in that it also comprises a local anesthetic.
8. 8. The topical pharmaceutical composition according to claim 7, characterized in that the local anesthetic is selected from the group consisting of lidocaine, bupivacaine, mepivacaine, ropivacaine, tetracaine and benzocaine.
9. 9. A method for providing peripheral analgesia to a mammal, characterized in that it comprises topical administration of a dose to attenuate or prevent tolerance of at least one NMDA receptor antagonist before, concurrently, or after topical administration of at least one an analgesic that works through an opioid receptor.
10. 10. The method according to claim 9, characterized in that the NMDA receptor antagonist is selected from the group consisting of dextromethorphan, dextrorphan, ketamine, pyroloquinoline quinone, cis-4- (phosphonomethyl) -2-piperidine carboxylic acid, MK801, memantine. , and mixtures thereof and pharmaceutically acceptable salts thereof.
11. The method according to claim 9, characterized in that the analgesic is selected from the group consisting of an opioid, an opiate derivative, an opioid, encephaliñas and endorphins.
12. The method according to claim 11, characterized in that the opioid is selected from the group consisting of ethylmorphine, hydromorphine, morphine, oxymorphone, codeine, levorphanol, oxycodone, pentazocine, propoxyphene, fentanyl, sufentanil, lofentanil, morphin-6. glucuronide and buprenorphine.
13. The method according to claim 9, characterized in that the enkephalin is selected from the group consisting of [D-Ala2, MePhe4, Gly (ol) 5] enkephalin, and ertdomorphins.
14. The method according to claim 9, characterized in that the NMDA receptor antagonist is administered in a dose of about 0.1% up to about 5%.
15. 15. A method for producing --analgesia to a mammal with preexisting tolerance to an analgesic, characterized in that it comprises the topical administration of an effective dose to reverse the tolerance of at least one NMDA receptor antagonist concurrently or after topical or systemic administration of at least one analgesic that works through an opioid receptor.
16. 16. A pharmaceutical, analgesic, inhibiting tolerance device, characterized in that it comprises: (a) a topical or systemic pharmaceutical composition comprising at least one analgesic that functions through an opioid receptor; and (b) a topical pharmaceutical composition comprising at least one NMDA receptor antagonist that inhibits tolerance.
17. 17. A method for providing analgesia to a mammal, characterized in that it comprises the topical administration of at least one analgesic that functions through the opioid receptor prior to, concurrently, or following the systemic or intrathecal administration of a second analgesic that functions through of the opioid receptor.
18. 18. The method according to claim 17, characterized in that it further comprises the topical administration of a dose to attenuate or prevent the tolerance of at least one NMDA receptor antagonist. SUMMARY OF THE INVENTION A topical opioid paradigm was developed to determine the peripheral analgesic effects of morphine. Topical morphine as well as peptides such as [D-Ala2, MePhe4, Gly (ol) 5] enkephalin (DAMGO) produced a potent, dose-dependent analgesia, using the tail blow test of radiant heat. Topical drugs potentiated the systemic agents, in a similar way to the previously established synergy between peripheral and central sites of action. Local tolerance quickly resulted from repeated daily topical exposure to morphine. Tolerance to topical morphine was effectively blocked by antagonists of the N-Methyl-D-Aspartate (NMDA) MK801 and ketamine receptors given either systemically or topically. The NMDA receptor antagonists reversed tolerance to pre-existing morphine. The activity of topical NMDA antagonists to block tolerance to local morphine suggests that peripheral NMDA receptors mediate tolerance to topical morphine. Morphine was cross-tolerant to [D-Ala2, MePhe4, Gly (ol) 5] enkephalin (DAMGO) but not morphin-6β-glucuronide, implying different mechanisms of action. Those ot / ni l- 48 observations are of great importance in the design and use of opioids clinically. Topical pharmaceutical compositions are described which comprise an analgesic that functions through an opioid receptor and an antagonist NMDA receptor to produce analgesia without inducing tolerance.