AU724714B2 - Methods and compositions of (+) doxazosin for the treatment of hypertension and benign prostatic hyperplasia - Google Patents

Description

aI S F Ref: 299950D1

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECFICATION FOR A STANDARD PATENT

ORIGINAL

Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: Sepracor, Inc.

33 Locke Drive Marlborough Massachusetts 01752 UNITED STATES OF AMERICA Nancy M. Gray Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Methods and Compositions of Doxazosin for the Treatment of Hypertension, Benign ProDtatic HUyprplaia and Atherosclerosis i and benT prosAcic hpprplctsio p.

The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845 Methods and Compositions of (+)Doxazosin for the Treatment of Hypertension and Benign Prostatic Hyperplasia Background of the Invention This invention relates to novel compositions of matter containing optically pure (+)doxazosin. These compositions possess potent long lasting anti-hypertensive activity while avoiding adverse effects associated with the administration of the racemic mixture of doxazosin including but not limited to orthostatic hypotension, nausea, lethargy, fatigue and dizziness. These compositions are of utility in the treatment of patients with benign prostatic hyperplasia (BPH) or in the treatment of patients with elevated serum low density lipoprotein (LDL) levels. Pure (+)doxazosin exhibits little of the hypotensive activity associated with the (-)enantiomer and is therefore superior to racemic doxazosin for these indications.

Also disclosed are methods for treating hypertension in a human while avoiding adverse effects that are associated with the racemic mixture of doxazosin by administering the isomer of doxazosin to said human. Also disclosed are methods for treating BPH and elevated LDL in a human while avoiding the hypotensive effects that are associated with the racemic mixture of doxazosin by administering the isomer of doxazosin to said human.

The active compound of these compositions and methods is an optical isomer of doxazosin, which is described by Young and Brogden in Drugs 35, 525-541 (1988) and US 4 188 390. Chemically, the active compound is the isomer of 4amino-2-[4-(1, 4 -benzodioxan-2-carbonyl)piperazin-1 -yl]- 6 ,7-dimethoxyquinazoline also known as 1-( 4 -amino-6,7-dimethoxy-2-quinazolinyl)-4-[(2,3-dihydro-1,4benzodioxan-2-yl)carbonyl]piperazine hereinafter referred to as doxazosin.

5 (+)Doxazosin, which is the subject of the present invention, is available commercially only as the 1:1 racemic mixture. That is, (+)doxazosin is available only as a mixture of optical isomers, called enantiomers. The racemic mixture of doxazosin is commercially available for administration as a methanesulfonate o (mesylate) salt, but extensive pharmacology has been published on the hydrochloride salt as well.

Many organic compounds exist in optically active forms, ie. they have the ability to rotate the plane of plane-polarised light. In describing an optically active compound, the prefixes D and L or R and S are used to denote the absolute configuration of the molecule about its chiral centre(s). The prefixes d and I or and are employed to designate the sign of rotation of plane-polarised light by the compound, with or I meaning that the compound is laevorotatory. A compound prefixed with or d is dextrorotatory. There is no correlation between nomenclature for the absolute stereochemistry and for the rotation of an enantiomer. Thus, D-lactic acid is the same as lactic acid, and L-lactic acid is S2 For a given chemical structure, these compounds, called stereoisomers, are identical except that they are mirror images of one another. A specific stereoisomer may also be referred to as an enantiomer, and a mixture of such isomers is often called an enantiomeric or racemic mixture.

Doxazosin is a representative of a group of drugs that block a, adrenoceptors. al receptors are innervated by postganglionic sympathetic neuronal fibres and are located in many body systems, including the cardiovascular system, where they are found primarily on smooth muscle cells in arterioles and venous capacitance vessels and the urinary tract. Activation of these receptors by the physiological neurotransmitter substance, norepinephrine, increases peripheral arteriolar resistance and decreases venous capacitance. Specific al antagonists act to lower blood pressure and this is their primary current clinical indication.

Historically, al antagonists such as phenoxybenzamine and phentolamine were not particularly useful as antihypertensive agents largely because of the 15 substantial tachycardia which accompanied their use. The tachycardic effect was however due primarily to the concomitant presynaptic a 2 receptor blocking activity of the early a antagonists. Inhibition of a 2 receptors acts presynaptically to augment the release of norepinephrine from adrenergic neurons. This stimulated the postjunctional sympathetic adrenoreceptors in the heart which are predominantly of the 20 p adrenergic type. New, more specific, a, receptor antagonists produce much less tachycardia than the older compounds. During long term therapy the vasodilatation persists with the newer a antagonists, but the remaining tachycardia, renin release and increased cardiac output, which are all reflex mediated, return to normal. In addition, there may be a component to al receptor inhibition that contributes to the amelioration of the reflex mediated mechanisms.

A troublesome cardiovascular problem related to the use of ai receptor antagonists is orthostatic hypotension. Symptomatic orthostatic hypotension is most likely to occur with high initial doses of al antagonists or may occur when the dose is increased rapidly. A modest degree of fluid retention which is another result of vasodilatation may also be observed when a, antagonists are used as single agents.

Doxazosin is a selective al adrenergic receptor blocking agent structurally related to prazosin. Its oral bioavailability is good and the plasma half life in man is approximately 10 hours following both oral and intravenous administration.

Evidence is now beginning to accumulate that there are subtypes of ai receptors, making ai adrenergic receptors a family of recognition units rather than a monolithic element. Bylund [FASEB J. 6,832-839 (1992)] has presented evidence that there are at least three presently differentiable ai receptor subtypes. Prazosin an achiral analog of doxazosin, is reported to have similar affinities for each of these subtypes.

libc03478 3 0 0 N *0 N6- O MeO N N 0 MeO N N MeO MeO

NH

2

NH

2 I II Doxazosin has a single chiral centre (shown in formula I) located on the carbon adjacent to the carboxyl group. This gives rise to a pair of enantiomers which have been resolved by Ley et al. [Recent Advances in Chiral Separations, Steven and Wilson Editors, Plenum Press, New York (1991) pages 97-103] on an analytical scale. US 4 188 390 described the synthesis of the two enantiomers, but provided no data on their pharmacology. In a subsequent article, Campbell Med.

Chem. 30, 49-57 (1987)] discussed the pharmacology of the two enantiomers and 10 concluded that there did not appear to be a stereoselective interaction with the *receptor.

Campbell et al. Med. Chem. 30, 49-57 (1987)] discloses racemic doxazosin and each of its enantiomers. Campbell states that both enantiomers "showed similar activity, which does not support a stereoselective interaction with the receptor". Mandal and Vaidyanathan [Indian J. Urol. 6, 45-50 (1990)], in a discussion of non-operative management of BPH, disclose that clinical trials were being designed to evaluate the therapeutic efficacy of doxazosin for the treatment of symptomatic BPH. Chapple [British Med. J. 304, 1198-1199 (1992)] states that longer term studies have investigated a series of a-adregneric blockers for the treatment of benign prostatic hyperplasia. Doxazosin is included in the list, and a conclusory statement suggests that racemic doxazosin may have been among the agents that significantly improved urinary flow rate.

In a series of articles [Schweiz. Med. Wochenschr. 120, 131-134 (1990); Pharmaceutisch Weekblad 125, 552-5554 (1990); and Eur. J. Clin. Pharm. 41, 89- 93 (1991)] Prof. E.J. Ariens describes the concept of eutomers and distomers and urges that pharmacology be carried out and reported on single enantiomers. He further suggests that regulatory authorities should require the separate testing of enantiomers. Testa and Trager [Chirality 2, 129-133 (1990)] suggest a paradigm for determining whether a racemate or a single enantiomer should be developed as a drug. They indicate that a basis for deciding can be found by examining the stereoselectivity in wanted and unwanted effects.

Although the inventor does not wish to be bound by a theoretical construct, it is possible that the beneficial effects of (+)doxazosin in increasing urine flow and bladder evacuation and in improving serum lipid profiles with minimal effects on libc03478

I

4 such other cardiovascular parameters as blood pressure and heart rate arise from the selective inhibition of a specific subset of cc receptors by the isomer as compared to its enantiomer, which may preferentially inhibit those subsets involved in regulating blood pressure.

The racemic mixture of doxazosin is presently used primarily as an antihypertensive agent. Doxazosin's oral bioavailability is good and the plasma half life in man is approximately 10 hours following both oral and intravenous administration. In addition, there is a report that the administration of doxazosin leads to modestly decreased total cholesterol and LDL levels. [Young Brogden Drugs 35, 525-541 (1988) and references therein.] There is also a report of the use of prazosin (11) to treat BPH [Hedlund et al., J. Urology 140, 275-278 (1983)] However, neither of the drugs has enjoyed widespread use for either BPH or improvement of serum lipid profiles because of the cardiovascular effects that are the primary result of their administration.

15 A troublesome cardiovascular problem related to the use of previously known al receptor antagonists for the treatment of BPH and the improvement of serum lipid profiles is their hypotensive activity, which is particularly reflected in the problem of orthostatic hypotension. Symptomatic orthostatic hypotension is most likely to occur with high initial doses of earlier al antagonists or may occur when the S 20 dose is increased rapidly. A modest degree of fluid retention, which is another result of vasodilation, may be observed. Reflex tachycardia is also occasionally observed.

Many of the cc antagonists cause somewhat similar adverse effects. The incidence of reported side effects associated with racemic doxazosin-treated patients has varied among studies. The incidence of total side effects associated S* with doxazosin in patients treated for hypertension has ranged between 0 and but has generally been similar to that seen with other anti-hypertensive agents at dosages producing a similar reduction in blood pressure. The most frequently reported side effects have been postural hypotension, nausea, lethargy, fatigue and dizziness.

Thus it would be particularly desirable to find a compound with the advantages of the racemic mixture of doxazosin which would not have the aforementioned disadvantages.

It would be particularly desirable to find an al antagonist that exhibited the beneficial effect on serum lipids hinted at by the racemic mixture of doxazosin but which would not have effects on blood pressure and heart rate. It would also be desirable to find a superior and selective al antagonist for the treatment of BPH.

libc03478 Summary of the Invention It has now been discovered that the optically pure (+)isomer of doxazosin is an effective antihypertensive that avoids adverse effects associated with the administration of the racemic mixture, including but not limited to postural hypotension, nausea, lethargy, fatigue and dizziness. The present invention also includes methods for treating hypertension in a human while avoiding the adverse effects that are associated with the racemic mixture of doxazosin, by administering the optically pure (+)isomer of doxazosin to said human.

It has now been discovered that the optically pure (+)isomer of doxazosin is an effective agent ior the treatment of BPH that avoids the hypotensive effects of racemic doxazosin. It is also an it effective agent for the improvement of serum lipid profiles that avoids the adverse effects associated with the administration of the racemic mixture. The present invention also includes methods for treating BPH in a human while avoiding the cardiovascular effects that are associated with the racemic mixture of doxazosin, by administering the optically pure (+)isomer of doxazosin to said human.

Accordingly, a first aspect of the present invention provides a method for eliciting an increase in urine flow in a human and at the same time reducing or eliminating undesirable side effects associated with racemic doxazosin, which method comprises administering to a human in need of increased urine flow a therapeutically effective amount of (+)doxazosin, or a pharmaceutically acceptable salt thereof, containing less than 10% by weight of (-)doxazosin.

20 A second aspect of the present invention provides a method of eliciting an increase in urine flow in a human while avoiding the concomitant liability of hypotensive effects associated with racemic doxazosin, which comprises administering to a human an amount of (+)doxazosin, or a pharmaceutically acceptable salt thereof, substantially free of its (-)stereoisomer, said amount being *to* sufficient to increase urine flow but insufficient to cause said hypotensive effects.

25 A third aspect of the present invention provides a method of eliciting an increase in urine flow in a human and at the same time reducing or eliminating the concomitant liability of hypotensive effects •associated with racemic doxazosin, which comprises administering to a human in need of increased

A

urine flow a therapeutically effective amount of (+)doxazosin, or a pharmaceutically acceptable salt thereof, containing less than 10% by weight of (-)doxazosin.

A fourth aspect of the present invention provides the use of (+)doxazosin, containing less than by weight of (-)doxazosin, for the manufacture of a medicament for eliciting an increase in urine flow in a human and at the same time reducing or eliminating the concomitant liability of hypotensive effects associated with racemic doxazosin.

[R:\LIBA]02943.doc:TLT A fifth aspect of the present invention provides the use of (+)doxazosin, containing less than by weight of (-)doxazosin, for the manufacture of a medicament for the treatment of benign prostatic hyperplasia in a human and at the same time for reducing or eliminating undesirable side effects associated with racemic doxazosin.

A sixth aspect of the present invention provides (+)doxazosin containing less than 10% by weight of (-)doxazosin when used for eliciting an increase in urine flow in a human and at the same time reducing or eliminating undesirable side effects associated with racemic doxazosin.

A seventh aspect of the present invention provides (+)doxazosin containing less than 10% by weight of (-)doxazosin when used for the treatment of benign hyperplasia in a human and at the same time a for reducing or eliminating undesirable side effects associated with racemic doxazosin.

Detailed Description of the Invention The present invention encompasses a method of treating hypertension in a human, which comprises administering to a human in need of such antihypertensive therapy, an amount of (+)doxazosin, or a pharmaceutically acceptable salt thereof, substantially free of its (-)stereoisomer, said amount being sufficient to alleviate hypertension. The method avoids the concomitant liability of adverse effects associated with the administration of racemic doxazosin by providing an amount of (+)doxazosin which is insufficient to cause the adverse effects associated with the racemic mixture of doxazosin.

The present invention also encompasses an antihypertensive composition for the treatment of a 20 human in need of antihypertensive therapy, which comprise an amount of (+)doxazosin, or a I"4: pharmaceutically acceptable salt thereof, substantially free of its (-)stereoisomer, said amount being sufficient to alleviate said hypertension but insufficient to cause the adverse effects associated with racemic doxazosin.

The present invention encompasses a method of eliciting an increase in urine flow in a human, 25 while avoiding the concomitant liability of hypotensive effects associated with the administration of racemic doxazosin, which comprises administering to a human an amount of (+)doxazosin, or a pharmaceutically acceptable salt thereof, substantially free of its (-)stereoisomer, said amount being sufficient to increase urine flow, but insufficient to cause the hypotensive effects associated with the racemic mixture of doxazosin.

[R:\LIBA]02943.doc:TLT tI( 6 The present invention also encompasses a composition for increasing urine flow in a human, which comprises an amount of (+)doxazosin, or a pharmaceutically acceptable salt thereof, substantially free of its stereoisomer, said amount being sufficient to increase urine flow but insufficient to causes the hypotensive effects associated with racemic doxazosin.

The present invention also encompasses a method of lowering plasma cholesterol and low density lipoprotein levels in a human while avoiding the concomitant liability of adverse effects associated with racemic doxazosin, which comprises administering to a human an amount of (+)doxazosin, or a pharmaceutically acceptable salt thereof, substantially free of its stereoisomer, said amount being sufficient to lower the cholesterol and LDL levels but insufficient to cause the adverse effects associated with racemic doxazosin.

The present invention also encompasses a composition for lowering serum cholesterol and low density lipoprotein in humans, which comprises an amount of S 15 (+)doxazosin or a pharmaceutically acceptable salt thereof, substantially fee of its stereoisomer, said amount being sufficient to lower serum low density lipoproteins, but insufficient to cause adverse effects associated with the administration of racemic doxazosin.

The available racemic mixture of doxazosin (ie. a 1:1 racemic mixture of the 20 two enantiomers) possesses antihypertensive activity and provides therapy and a reduction of symptoms in conditions and disorders related to hypertension; however, this racemic mixture, while offering the expectation of efficacy, causes adverse effects. Utilising the substantially optically pure or optically pure isomer of doxazosin results in clearer dose related definitions of efficacy, diminished adverse effects, and accordingly, an improved therapeutic index. It is therefore more S* desirable to administer the isomer of doxazosin than racemic doxazosin.

In addition, racemic doxazosin has been shown to improve the profile of serum lipoproteins in humans. Epidemiological studies have indicated that high concentrations of high density lipoprotein (HDL) cholesterol are a negative risk factor for coronary artery disease, while high concentrations of low density lipoprotein (LDL) cholesterol are a positive risk factor. During doxazosin administration to hypertensive patients there has been a trend to an increase in high density lipoprotein cholesterol and in HDL/total cholesterol ratio and to a decrease in plasma total cholesterol and triglycerides. Changes relative to baseline were occasionally significant for HDL/total cholesterol ratio, triglycerides and total cholesterol. The effect was evident after 12 weeks' treatment and was maintained for up to 1 year. Unfortunately, the strong hypotensive effects of racemic doxazosin make the presently available drug unattractive for the purpose of improving lipoprotein profiles in the prevention and treatment of coronary artery disease. The use of the substantially pure isomer makes possible the desired favourable libc03478 effect on serum lipoprotein profiles while eliciting diminished cardiovascular activity.

"Cardiovascular" activity encompasses hypotension, vasodilation, tachycardia, and increased cardiac output.

The smooth muscles of the human bladder neck, bladder base, urethra and prostatic capsule are innervated sympathetically, and contraction-mediating aadrenoceptors have been demonstrated in these structures. It has been suggested c that urinary retention as the result of increasing outlfow obstruction in benign prostatic hyperplasia may be caused partly by stimulation of prostatic aadrenoceptors. Supporting this view, favourable results have been reported during treatment with the a-adrenoceptors blocker phenoxybenzamine and prazosin.

Isolated human urethra contracted by noradrenaline is relaxed completely by prazosin. Furthermore, prazosin exerts an a-adrenoceptor blocking effect on both human prostatic adenoma tissue and prostatic capsule tissue in vitro. Thus if stimulation of a-adrenoceptors contributes to the obstruction of benign prostatic 15 hyperplasia, their blockade ought to be effective therapeutically, and, in fact, prazosin has been shown to improve urinary flow and bladder evacuation in patients suffering from benign prostatic hyperplasia. There are no reports of the use of doxazosin for this indication. The use of substantially pure (+)doxazosin makes possible the improvement in urinary flow and bladder evacuation without the 20 concomitant cardiovascular activity of classical ac antagonists and racemic doxazosin. It is therefore, more desirable to administer the isomer of doxazosin than racemic doxazosin.

The term "adverse effects" includes, but is not limited to postural hypotension, nausea, lethargy, fatigue and dizziness. Other side effects that have been reported with doxazosin include headache, blurred vision, oedema, chest discomfort, constipation, dry mouth, sexual dysfunction, anxiety or nervousness, insomnia, palpitations, tachycardia, rash, paraesthesia, muscle cramps, increased sweating, conjunctivitis, diarrhoea, flatulence, dyspnoea, neutropenia, leucopoenia, rhinitis and increased frequency of micturition.

The term "substantially free of its stereoisomer" as used herein means that the compositions contain a greater proportion of the isomer of doxazosin in relation to the isomer. In a preferred embodiment, the term "substantially free of its isomer" as used herein means that the composition is at least 90% by weight of (+)doxazosin and 10% by weight or less of (-)doxazosin. In a more preferred embodiment the term "substantially free of the stereoisomer" means that the composition contains at least 99% by weight of (+)doxazosin, and 1% or less of (-)doxazosin. In the most preferred embodiment, the term "substantially free of its stereoisomer" as used herein means that the composition contains greater than 99% by weight of (+)doxazosin. These percentages are based upon the total amount of doxazosin in the composition. The terms "substantially optically pure libc03478 18 isomer of doxazosin or "substantially optically pure (+)doxazosin" and "optically pure isomer of doxazosin and "optically pure (+)doxazosin" are also encompassed by the above-described amounts.

The chemical synthesis of the racemic mixture of doxazosin can be performed by the method described in US 4 188 390. The individual enantiomers of doxazosin may be obtained by resolution of the racemic mixture of enantiomers using conventional means. The doxazosin may be resolved with an optically active acid such as tartaric acid at the N-(1,4-benzodioxan-2-carbonyl)piperazine intermediate stage or at the final product. Alternatively the benzodioxan- carboxylic acid intermediate can be resolved with an optically active base such as brucine or aphenethylamine. Other standard methods of resolution known to those skilled in the art, including but not limited to simple crystallisation and chromatographic resolution, can be used. [See for example, Stereochemistry of Carbon Compounds, E.L. Eliel, McGraw Hill (1962); "Tables of Resolving Agents" Wilen and Lochmuller, 15 J. Chromatography 113, 283-302 (1975).] Additionally, the optically pure isomer can be prepared from the racemic mixture by enzymatic biocatalytic resolution. See for example, US 5 057 427 and 5 077 217, the disclosures of which are 9 .incorporated herein by reference.

The magnitude of a prophylactic or therapeutic dose of (+)doxazosin in the 20 acute or chronic management of disease will vary with the severity of the condition to be treated, and the route of administration. The dose, and perhaps the dose frequency, will also vary according to the age, body weight, and response of the individual patient. In general, the total daily dose range, for (+)doxazosin, for the conditions described herein, is from about 0.1mg to about 20mg, in single or divided doses. Preferably, a daily dose range should be between about 0.1mg to about or between about 0.1mg to about 8mg, in single or divided doses, while most preferably, a daily dose range should be between about 0.5mg to about 5mg, in single or divided doses. In managing the patient, the therapy should be initiated at a lower dose, perhaps about 0.5mg to about 1mg, and increased up to about 8mg or higher depending on the patient's global response. It is further recommended that children, and patients over 65 years, and those with impaired renal, or hepatic function, initially receive low doses, and that they be titrated based on individual response(s) and blood level(s). It may be necessary to use dosages outside these ranges in some cases as will be apparent to those skilled in the art. Further, it is noted that the clinician or treating physician will know how and when to interrupt, adjust, or terminate therapy in conjunction with individual patient response. The term "an amount sufficient to alleviate hypertension but insufficient to cause said adverse effects" is encompassed by the above-described dosage amounts and dose frequency schedule. The terms "an amount sufficient to increase urine flow but insufficient to cause said hypotensive effects" and "an amount sufficient to lower libc03478 cholesterol and LDL levels but insufficient to cause adverse effects" are encompassed by the above-described dosage amounts and dose frequency schedule.

Any suitable route of administration may be employed for providing the patient with an effective dosage of (+)doxazosin. For example, oral, rectal, parenteral (subcutaneous, intramuscular, intravenous), transdermal, and like forms of administration may be employed. Dosage forms include tablets, troches, dispersions, suspensions, solutions, capsules, patches, and the like.

The pharmaceutical compositions of the present invention comprise (+)doxazosin as the active ingredient, or a pharmaceutically acceptable salt thereof, and may also contain a pharmaceutically acceptable carrier, and optionally, other therapeutic ingredients.

The terms "pharmaceutically acceptable salts" or "a pharmaceutically acceptable salt thereof" refer to salts prepared from pharmaceutically acceptable non-toxic acids or bases including inorganic acids and bases and organic acids and bases. Since the compound of the present invention is basic, salts may be prepared from pharmaceutically acceptable non-toxic acids including inorganic and organic acids. Suitable pharmaceutically acceptable acid addition salts for the compound of the present invention include acetic, benzenesulfonic (besylate), benzoic, S 20 camphorsulfonic, citric, ethenesulfonic, fumaric, gluconic, glutamic, hydrobromic, hydrochloric, isethionic, lactic, maleic, malic, mandelic, methanesulfonic (mesylate), mucic, nitric, pamoic, pantothenic, phosphoric, succinic, sulfuric, tartaric, ptoluenesulfonic, and the like.

The compositions of the present invention include compositions such as suspensions, solutions, elixirs, aerosols, and solid dosage forms. Carriers such as starches, sugars, microcrystalline cellulose, diluents, granulating agents, lubricants, binders, disintegrating agents, and the like, are commonly used in the case of oral solid preparations (such as powders, capsules, and tablets), with the oral solid preparations being preferred over the oral liquid preparations. The most preferred oral solid preparation is tablets.

Because of their ease of administration, tablets and capsules represent the most advantageous oral dosage unit form, in which case solid pharmaceutical carriers are employed. If desired, tablets may be coated by standard aqueous or nonaqueous techniques.

In addition to the common dosage forms set out above, the compounds of the present invention may also be administered by controlled release means and/or delivery devices such as those described in US 3 845 770; 3 916 899; 3 536 809; 3 598 123; and 4 008 719; the disclosures of which are hereby incorporated by reference.

libc03478 4 Pharmaceutical compositions of the present invention suitable for oral administration may be presented as discrete units such as capsules, cachets, or tablets, or aerosol sprays, each containing a predetermined amount of the active ingredient, as a powder or granules, or as a solution or a suspension in an aqueous S 5 liquid, a non-aqueous liquid, an oil-in-water emulsion, or a water-in-oil liquid emulsion. Such compositions may be prepared by any of the methods of pharmacy, but all methods include the step of bringing into association the active ingredient with the carrier which constitutes one or more necessary ingredients. In general, the compositions are prepared by uniformly and intimately admixing the active ingredient with liquid carriers or finely divided solid carriers or both, and then, if necessary, shaping the product into the desired presentation.

For example, a tablet may be prepared by compression or moulding, optionally, with one or more accessory ingredients. Compressed tablets may be prepared by compressing in a suitable machine the active ingredient in a free- S 15 flowing form such as powder or granules, optionally mixed with a binder, lubricant, inert diluent, surface active or dispersing agent. Moulded tablets may be made by moulding in a suitable machine, a mixture of the powdered compound moistened with an inert liquid diluent. Desirably, each tablet contains from about 0.5mg to about 10mg of the active ingredient. Most preferably, the tablet, cachet or capsule .,It 20 contains either one of three dosages, about 0.5mg, about 2mg, or about 8mg of the active ingredient.

The invention is further defined by reference to the following examples describing in detail the preparation of the compositions of the present invention as well as their utility.

Example Procedures ai-Adrenergic Binding Assay Whole brains are obtained from male Wistar rats. After removal of the cerebellum, the brains are used to prepare the membrane fraction (see Greengrass, P. and Brenner, R. Eur. J. Pharmacol. 55: 323-326, 1979). The membrane preparation (10mg) is incubated with 0.25nM 3 H]-prazosin and varying concentrations of test substance for 30 minutes at 25 0 C. Membranes are filtered and washed 3 times and the filters counted to determine the amount of 3

H]-

prazosin specifically bound. Non-specific binding is determined by incubation with 0.1pM prazosin.

2 -Adrenergic Binding Assay Brain cortices are removed from male Wistar rats and a membrane fraction is prepared (see Boyajian, C.L. and Leslie, F.M. J. Pharmacol. Exp. Ther. 241: 1092 1098, 1987). The membrane preparation (10mg) is incubated with 0.7nM [3H]rauwolscine and varying concentrations of test substance for 30 minutes at 25 0

C.

libc03478 Membranes are filtered and washed 3 times and the filters counted to determine the amount of 3 H]-rauwolscine specifically bound. Non-specific binding is determined by incubation with 1lpM yohimbine.

A) Antihypertensive Efficacy in Spontaneously Hypertensive Rats S 5 Male spontaneously hypertensive rats (300-350g) are anaesthetised, and Spolyethylene catheters are implanted in the abdominal aorta via a femoral artery and in the abdominal vena cava via a femoral vein.

The arterial catheters are connected to pressure transducers by means of an intraflow device, flushing the catheters with 3mL/h. Mean arterial pressures are derived electronically from the blood pressure wave. Mean pretreatment values of mean arterial pressure are in the range of 160-220mm Hg. Doses of racemic doxazosin, (+)doxazosin and (-)doxazosin, or of the solvent vehicle, are injected into the venous catheter. Responses in mean arterial pressure to the respective drug or solvent are registered and the relative potencies of the test compounds are calculated.

Test1 A test for activity in lowering serum LDL and cholesterol is carried out according to the method of Havel et al. [Arteriosclerosis 2, 467-474 (1982)].

Homozygous Watanabe-heritable hyperlipidemic (WHHL) rabbits are 20 maintained on Purina Rabbit Laboratory Chow and used at 3-5 months of age.

Blood is collected from the ear veins of unanesthetised rabbits or from the abdominal aorta of anaesthetised rabbits and placed on ice. Lipoproteins are separated from plasma by sequential ultracentrifugation. For analysis of lipoprotein composition and for separation of protein components, samples are recentrifuged at their upper density limits.

Total cholesterol and triglycerides are estimated in plasma, and lipoprotein fractions by the automated technique of Rush et al. [Rush RL, Leon L, Turrel J.

"Automated simultaneous cholesterol and triglyceride determination on the autoanalyser II instrument". In: Advances in Automated Analysis-Technicon International Congress-1970/Clinical Analysis. Mt. Kisco: Futura, 1970; 1:503-507] For measurements of lipoprotein composition, one can also estimate free and esterified cholesterol, phospholipids, and protein.

Test 2 A test for vascular dilatation is carried out as follows: New Zealand White rabbits, weighing 2.0 to 2.5kg, are sacrificed by cervical dislocation and the thoracic aortas excised immediately. The aortas are then immersed in warm, oxygenated Krebs-bicarbonate solution and cut in transverse or spiral strips, 1 to 3mm in width.

The strips are suspended vertically in tissue baths containing an isotonic bicarbonate buffer. The composition of this buffer may be as follows (amount in libcO3478 12 millimoles per litre): NaCI, 119.0; KCI, 4.7; CaCI 2 2.5; MgSO 4 1.5; KH 2

PO

4 1.2; NaHCO 3 25.0; and dextrose, 11.0. The bathing medium is aerated with 95% 02 and 5% C02 and maintained at 37.0+0.50C and pH7.4. The lower end of each strip is secured to a tissue holder and the upper end attached via a string or a fine chain to a force-displacement transducer; responses are displayed on recorders. Tissues are placed under an initial tension of 0.1 to 2.Og and permitted to stretch and equilibrate before testing. The tension on the strips is readjusted intermittently to the initial tension during the equilibration period. Drugs are introduced into the tissue baths with syringes or pipettes and removed by drainage and replacement of the bathing medium from preheated, oxygenated reservoirs. Responses are expressed as gram changes in tension above base-line.

The response of the tissue to lp g/mL phenylephrine is measured. The tissue is incubated with varying concentrations of the test substances and the response to phenylephrine re-evaluated. Alternatively the tissues are precontracted with an (X- 15 receptor stimulator such as phenylephrine and relaxed by gradual additions of a test substance to the bath fluid.

The-" Test 3 The procedure analogous to the one described above is repeated using canine urethral tissue in place of rabbit aorta to determine potential urinary tract 20 effects.

Test 4 A test for insulin resistance is carried out as an indication of favourable changes in serum lipid levels. Castelli, American Heart Journal, 112: 432-40 (1986) and McKeigne et al, British Heart Journal, 60: 390-96 (1998) have shown that insulin resistance and hyperinsulinemia lead to decreases in plasma HDL cholesterol concentrations and increases in plasma triglyceride levels. The beneficial effects of doxazosin on plasma lipids are therefore consistent with pervious findings of a decreased insulin resistance in a man after dosing with doxazosin, and a test protocol which measures insulin resistance correlates with an expectation of similar responses in serum lipids in vivo.

Insulin is a hormone that activates various biochemical processes in the body, the most well known being facilitation of glucose transport over cell membranes and activation of cell growth. The development of insulin resistance is common both in diabetics and nondiabetics, but it is only the glucose transport system that develops resistance to insulin. To compensate for the impaired glucose transport, the normal body produces more insulin and the diabetic patient has to inject higher doses of insulin. Since insulin also is a growth hormone, the increased insulin concentration induces an accelerated growth of atherosclerotic lesions and increased risk for cardiovascular morbidity and mortality.

libc03478 13 The present studies are performed in old, spontaneously hypertensive rats (SHRs), which are known to develop insulin resistance. Racemic doxazosin, (-)doxazosin, and (+)doxazosin are studied for their effects on glucose transport, insulin plasma concentration and arterial blood pressure.

Prior to receiving vehicle or test compound, basal measurements of the following parameters are made: systolic blood pressure (measured via tail cuff occlusion); fasting levels of plasma insulin and triglycerides; and glucose tolerance.

The SHRs receive vehicle or test compound via oral gavage once or twice daily or two or four weeks. Measurements of blood pressure, circulating insulin and triglycerides, and glucose clearance are made following two (and four) weeks of drug administration. Any changes in insulin resistance resulting from the drug treatment are evident as changes in the ratio of plasma glucose/plasma insulin levels and from the glucose tolerance tests.

15 Test A test for orthostatic hypotension and reflex tachycardia is carried out in dogs.

Groups of dogs are tested with suitable doses of racemic doxazosin, (-)doxazosin, and (+)doxazosin and the effects on blood pressure (orthostatic hypotension) and heart rate (reflex tachycardia) are monitored and recorded at predetermined time 20 intervals. Conscious normotensive dogs with surgically implanted arterial catheters are used to study the effects of the drugs on orthostatic hypotension and heart rate.

The animals may also be equipped with cutaneous electrodes connected to suitable equipment for recording electrocardiograms. The tip of the indwelling catheter is positioned at the junction between the aorta and the left carotid artery. Blood pressure is measured by means of a pressure transducer and heart rate is computed from the systolic peaks in blood pressure or from the R-waves of the i EKG. Doses of the test compounds are given orally or parenterally and the effects on the cardiovascular parameters are initially recorded with the animals in normal standing position. The animals are then held by their front paws and lifted into an upright position, standing on their hind paws. Drugs causing orthostatic hypotension will cause a sudden fall in recorded arterial blood pressure, sometimes accompanied by a reflex tachycardia.

Example 1 Oral Formulation Capsules: Formula Quantity per capsule in mg A B C (+)Doxazosin 0.5 2.0 Lactose 84 82.5 76.5 Cornstarch 15 15 Magnesium Stearate 0.5 0.5x' Compression Weight 100.0 100.0 100.0 libc03478 14 The active ingredient, (+)doxazosin, is sieved and blended with the excipients.

The mixture is filled into suitably sized two-piece hard gelatin capsules using suitable machinery. Other doses may be prepared by altering the fill weight and if necessary, changing the capsule size to suit.

Example 2 Oral Formulation Tablets: Formula Quantity per tablet in m A B C (+)Doxazosin 0.5 2.0 Lactose 72.25 70.75 64.75 Cornstarch 3.0 3.0. Water (per thousand Tablets)* 30.0mL 30.0mL 30.0mL Cornstarch 18.75 18.75 18.75 Magnesium Stearate 0.50 0.50 0.50 Compression Weight 125.0 125.0 125.0 *The water evaporates during manufacture So: The active ingredient is blended with the lactose until a uniform blend is formed. The smaller quantity of cornstarch-is blended with the water to form the 10 resulting cornstarch paste. This is then mixed with the uniform blend until a uniform wet mass is formed and the remaining cornstarch is added and mixed until uniform granules are obtained. The granules are screened through a suitable milling machine using a 6.35mm stainless steel screen. The milled granules are dried in a suitable drying oven and milled through a suitable milling machine again.

The magnesium stearate is then blended and the resulting mixture is compressed into tablets of desired shape, thickness, hardness and disintegration.

libc03478

Claims (8)

1. A method for eliciting an increase in urine flow in a human and at the same time reducing or eliminating undesirable side effects associated with racemic doxazosin, which method comprises administering to a human in need of increased urine flow a therapeutically effective amount of (+)doxazosin, or a pharmaceutically acceptable salt thereof, containing less than 10% by weight of )doxazosin.

2. The method of claim 1 wherein the human is in need of therapy for benign prostatic hyperplasia.

3. A method of eliciting an increase in urine flow in a human while avoiding the concomitant io liability of hypotensive effects associated with racemic doxazosin, which comprises administering to a human an amount of (+)doxazosin, or a pharmaceutically acceptable salt thereof, substantially free of its (-)stereoisomer, said amount being sufficient to increase urine flow but insufficient to cause said hypotensive effects.

4. A method for eliciting an increase in urine flow in a human and at the same time reducing is or eliminating the concomitant liability of hypotensive effects associated with racemic doxazosin, which comprises administering to a human in need of increased urine flow a therapeutically effective amount of (+)doxazosin, or a pharmaceutically acceptable salt thereof, containing less than 10% by weight of (-)doxazosin.

5. The use of doxazosin, containing less than 10% by weight of (-)doxazosin, for the 20 manufacture of a medicament for eliciting an increase in urine flow in a human and at the same time reducing or eliminating the concomitant liability of hypotensive effects associated with racemic doxazosin.

6. The use of (+)doxazosin, containing less than 10% by weight of (-)doxazosin, for the manufacture of a medicament for the treatment of benign prostatic hyperplasia in a human and at the 25 same time for reducing or eliminating undesirable side effects associated with racemic doxazosin.

7. (+)doxazosin containing less than 10% by weight of (-)doxazosin when used for eliciting an increase in urine flow in a human and at the same time reducing or eliminating undesirable side effects associated with racemic doxazosin.

8. (+)doxazosin containing less than 10% by weight of (-)doxazosin when used for the treatment of benign hyperplasia in a human and at the same time for reducing or eliminating undesirable side effects associated with racemic doxazosin. Dated 7 January, 2000 Sepracor, Inc. SPatent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON rR:\L1BA102943.doc:TLT