AU8728591A

AU8728591A - Use of endo-n-(8-methyl-8-azabicyclo{3.2.1}oct-3-yl)-2,3-dihydro-3, 3dimethylindole-1-carboxamide in the treatment of dependence and withdrawal syndrome

Info

Publication number: AU8728591A
Application number: AU87285/91A
Authority: AU
Inventors: Thomas Paul Blackburn; Brian John Jones
Original assignee: Beecham Group PLC
Current assignee: Beecham Group PLC
Priority date: 1990-10-17
Filing date: 1991-10-17
Publication date: 1992-05-20
Also published as: WO1992006689A1; JPH06501946A; IE913621A1; CA2094157A1; KR930702979A; EP0553160A1

Description

Use of endo-N-(8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-2,3-dihydro-3, 3dimethylindole-1-carboxamide in the treatment of dependence and withdrawal syndrome

The present invention relates to a method for the relief or prevention of a withdrawal syndrome resulting from addiction to a drug or substance of abuse and/or for the suppression of dependence on drugs or substances of abuse, and to the use of a compound in the preparation of a medicament for such method.

EP-0279114 relates to the use of compounds which act as antagonists of 5HT at 5-HT3 receptors for the relief or prevention of a withdrawal symptom resulting from addiction to a drug or substance of abuse and/or for the suppression of dependence on drugs or substances of abuse.

EP-0247266 discloses endo-N-(8-methvl-8-azabicvclo [3.2.1Joct-3-yl)-2,3-dihydro-3,3-dimethylindole-l- carboxamide (hereinafter called the Compound) and a process by which it can be prepared.

The Compound is described in EP-0247266 as having 5-HT M- receptor antagonist activity, anti-emetic activity and/or gastric motility enhancing activity.

It has now been shown that administration of the Compound can prevent, alleviate or reverse the withdrawal syndrome. The Compound is therefore of use for the prevention or relief of a withdrawal syndrome resulting from addiction to drugs or substances of abuse.

It has also been shown that the Compound suppresses dependence on drugs or substances of abuse. The Compound is therefore also of use in reducing the craving for a drug or substance of abuse after addition to that drug or substance, and can therefore be used for maintainence therapy during remission from addition to drugs or substances of abuse. The Compound may also be used for prophylactic treatment of subjects liable to become dependent on drugs or substances of abuses.

The effectiveness of the Compound for use according to the present invention in the treatment of a withdrawal syndrome resulting from addiction to a drug or substance of abuse, and for the suppression of dependence on a drug or substance of abuse, for example cocaine or benzodiazepines such as diazepam, may be demonstrated in animals using standard tests, for example, the light dark exploration test in mice, the rat social interaction test, a marmoset behavioural test, the 'drinkometer' alcohol consumption test in rats, and the cocaine discrimative stimulus paradigm in rats.

Accordingly, the present invention provides a method of treatment for the relief or prevention of a withdrawal syndrome resulting from addiction to a drug or substance of abuse and/or for the suppression of dependence on drugs or substances of abuse in mammals including humans, which method comprises administering an effective, non-toxic amount of the Compound or a pharmaceutically acceptable salt or solvate thereof to the mammal in need of such treatment.

The administration is preferably by way of a pharmaceutical composition.

Such compositions are prepared by admixture and are suitably adapted for oral or parenteral administration, and as such may be in the form of tablets, capsules, oral liquid preparations, powders, granules, lozenges, reconstitutable powders, injectable and infusable solutions or suspensions or suppositories. Orally administrable compositions are preferred, since they are more convenient for general use. Tablets and capsules for oral administration are usually presented in a unit dose, and contain conventional excipients such as binding agents, fillers, diluents, tabletting agents, lubricants, disintegrants, colourants, flavourings, and wetting agents. The tablets may be coated according to well known methods in the art, for example with an enteric coating.

Suitable fillers for use include cellulose, annitol, lactose and other similar agents. Suitable disintegrants include starch, polyvinylpolypyrrolidone and starch derivatives such as sodium starch glycollate. Suitable lubricants include, for example, magnesium stearate.

Suitable pharmaceutically acceptable wetting agents include sodium lauryl sulphate. Oral liquid preparations may be in the form of, for example, aqueous or oily suspensions, solutions, emulsions, syrups, or elixirs, or may be presented as a dry product for reconstitution with water or other suitable vehicle before use. Such liquid preparations may contain conventional additives such as suspending agents, for example sorbitol, syrup, methyl cellulose, gelatin, hydroxyethylcellulose, carboxymethylcellulose, aluminium stearate gel or hydrogenated edible fats, emulsifying agents, for example lecithin, sorbitan monooleate, or acacia; non-aqueous vehicles (which may include edible oils) , for example, almond oil, fractionated coconut oil, oily esters such as esters of glycerine, propylene glycol, or ethyl alcohol; preservatives, for example methyl or propyl p-hydroxybenzoate or sorbic acid, and if desired conventional flavouring or colouring agents.

Oral liquid preparations are usually in the form of aqueous or oily suspensions, solutions, emulsions, syrups, or elixirs or are presented as a dry product for reconstitution with water or other suitable vehicle before use. Such liquid preparations may contain conventional additives such as suspending agents, emulsifying agents, non-aqueous vehicles (which may include edible oils) , preservatives, and flavouring or colouring agents.

The oral compositions may be prepared by conventional methods of blending, filling or tabletting. Repeated blending operations may be used to distribute the active agent throughout those compositions employing large quantities of fillers. Such operations are, of course, conventional in the art.

For parenteral administration, fluid unit dose forms are prepared containing the Compound of the present invention and a sterile vehicle. The Compound, depending on the vehicle and the concentration, can be either suspended or dissolved. Parenteral solutions are normally prepared by dissolving the Compound in a vehicle and filter sterilising before filling into a suitable vial or ampoule and sealing. Advantageously, adjuvants such as a local anaesthetic, preservatives and buffering agents are also dissolved in the vehicle. To enhance the stability, the composition can be frozen after filling into the vial and the water removed under vacuum.

Parenteral suspensions are prepared in substantially the same manner except that the Compound is suspended in the vehicle instead of being dissolved and sterilised by exposure of ethylene oxide before suspending in the sterile vehicle. Advantageously, a surfactant or wetting agent is included in the composition to facilitate uniform distribution of the Compound of the invention.

An amount effective to treat the disorders hereinbefore described depends on the nature and severity of the disorder being treated and the weight of the mammal. However, a unit dose for a 70kg adult will normally contain 0.01 to lOOOmg for example 0.1 to 500mg, of the Compound of the invention. Unit doses may be administered once or more than once a day, for example, 2, 3 or 4 times a day, more usually 1 to 3 times a day, that is in the range of approximately 0.0001 to 50mg/kg/day, more usually 0.0002 to 25 mg/kg/day.

No adverse toxicological effects are indicated at any of the aforementioned dosage ranges.

The invention also provides a pharmaceutical composition which comprises an effective amount of the Compound or a pharmaceutically acceptable salt or solvate thereof for the relief or prevention of a withdrawal syndrome resulting from addiction to a drug or substance of abuse and/or for the suppression of dependence on drugs or substances of abuse.

Such composition may be prepared in the manner as described hereinbefore.

In a further aspect the invention provides the use of the Compound or a pharmaceutically acceptable salt or solvate thereof for the manufacture of a medicament for the relief or prevention of a withdrawal syndrome resulting from addiction to a drug or substance of abuse and/or for the suppression of dependence on drugs or substances of abuse.

Such manufacture and treatment may be carried out in the manner as described hereinbefore. Pharmacolocrical Data

1. Cocaine Discriminative Stimulus Paradiqin

Action of test compound on the behavioural effects of cocaine in male hooded Lister rats as measured in the cocaine discriminative stimulus paradigm.

METHODS

RATS

Nine male Hooded Lister rats initially weighing 200-250g were used throughout the experiment. They were housed in groups of four or five under a 12 hour light/dark cycle. The rats were fed according to a predetermined growth curve for this species so that their weights were maintained at 80-90% of their free feeding weights. Water was available ad lib. Training and test sessions were conducted five days per week.

APPARATUS

The apparatus consisted of a standard ventilated chamber (Campden instruments) contained in a sound-attenuated box.

The chamber was equipped with two retractable bars separated by a recess into which 45mg food pellets were dispensed.

Responses on the bars were automatically recorded by microcomputer.

TRAINING

The rats were initially trained to press the bars for food rewards on an FR-1 (fixed ratio 1) schedule of reinforcement in 15 min. training sessions. Under this schedule, one press on a bar resulted in one food pellet being dispensed to the rat. On alternate days, the left or right bar was presented to the rat. As the rats became adept at performing this task, the fixed ratio was increased incrementally up to FR- 10 (one reward for ten responses.

After the preliminary training had been established, drug discrimination training commenced. Cocaine (5.0 mg/kg ip) or saline (1.0 mg/kg ip) were injected and both bars were presented to each rat 15 minutes later. For each rat, one bar was paired with cocaine injection and the other bar was paired with vehicle (saline) injection. In order to balance for side preferences, cocaine was paired with the left bar for five rats and paired with the right bar for the remaining four rats. Vehicle injections were paired with the other bar. Under these conditions of the FR-10 schedule, each rat was rewarded if it accumulated 10 responses on the correct bar (depending on whether it had received cocaine or vehicle) . As discrimination training progressed, a VI (variable interval) was introduced into the reinforcement schedule. At the onset of the training session, during a randomly determined interval the rats were not rewarded on either bar. After this interval the schedule switched into the FR-10 component until the rats produced ten correct responses. The schedule then switched back to the VI component. This tandem schedule continued through each 15 min. training session. As the rats acquired the the cocaine discrimination, the VI was progressively increased to 60 seconds (VI-60; mean time = 60 sec; range = 14-108 sec.) In addition, a punishment schedule was included in the FR component which required the rat to respond on the correct bar on ten consecutive occasions in order to be rewarded. This minimised the possibility of the rats alternating between bars in order to gain food rewards by chance. Thus the final schedule of reinforcement was a tandem VI-60, FR- 10 with punishment. Training injections were made in a restricted randomised order such that no rat received more than three consecutive treatments of cocaine or saline, and over the period of training there was an equal number of cocaine and saline treatments

TESTS

After approximately 60 training sessions, discrimination control was achieved and tests were initiated. The rats were tested in 5 min. extinction sessions on Tuesdays and Fridays during which no food rewards were available. In order to maintain discrimination control, 15 min. training sessions were continued on intervening days such that the rats were trained after saline injection on Mondays and Thursdays and after cocaine injection on Wednesdays. This minimised the possiblity of residual cocaine effects being carried over on to test days. On the test days, the rats received pretreatment with test compound, (the Compound, hydrochloride salt) (0.0025, 0.005 or 0.01 mg/kg sc) or vehicle (saline l l/kg sc) 45 min. prior to test, and cocaine hydrochloride (2.5 mg/kg ip) or vehicle (saline lml/kg ip) 30 min. prior to test. These eight treatment combinations were administered in random order, and each rat received every treatment. After completion of this random scheme four extra treatments were conducted in which rats were pretreated with test compound (0.00125 or 0.02 mg/kg sc) 45 min. prior to test and cocaine hydrochloride (2.5 mg/kg ip) or vehicle (saline lml/kg ip) 30 min. prior to test.

DRUGS

Cocaine hydrochloride (Sigma) was dissolved in isotonic saline and injected in a volume of 1 ml/kg ip. Test compound was dissolved in isotonic saline and was injected in the flank in a volume of 1 ml/kg sc. Vehicle solutions were isotonic saline and were injected in a volume of 1 ml/kg ip (cocaine vehicle) and 1 ml/kg sc (test compound vehicle) . Drug doses are expressed as the base equivalent.

DATA PRESENTATION AND STATISTICAL ANALYSIS

The number of responses on the cocaine training bar was expressed as a percentage of the total number of responses accumulated on both bars in the 5 min. extinction tests. The total number of responses accumulated on both bars in the 5 min. extinction tests was also noted. Data was analysed by two factor analysis of variance with rat and treatment as the independent variables, and by Dunnett's t-test to allow for multiple comparisons with a control group.

RESULTS

Analysis of the results for the percent cocaine bar responses provided strong evidence that treatments affected responding (F(8,56)=32.2, P<0.001) . Responding after saline control was 11.8+_3.3%, and this was increased to 87.0+6.4% for the cocaine control (t(7)=9.96, P<0.01). Compared to the cocaine control, the 0.01 mg/kg dose of test compound significantly attenuated cocaine-appropriate responding (t(7)=4.73, P<0.01). The 0.0025 and 0.005 doses of test compound showed a similar trend although the results were not significant. The attenuation of cocaine-appropriate responding was never sufficient to reach the low levels seen with the saline control such that the percent responding with cocaine after the pretreatments with the different doses of test compound were still significantly higher than the responding after saline (lowest t(7)=9.46, P<0.01).

Analysis of the total responses indicated that treatment did not affect response rate (F(7,56)=0.99, p>0.4). DISCUSSION

The data reported here provide evidence that the test compound (0.01 mg/kg), significantly attenuated the interoceptive effects caused by cocaine in rats without producing full blockade. These effects were produced by doses of test compound which did not reduce response rates and therefore there was no evidence that the attenuation of the cue was due to confounding non-specific effects (eg anaesthesia, catalepsy, seizure activity) . The anxiolytic profile of the test compound together with the inhibitory effects on the cocaine cue demonstrated in this study suggest that this compound has potential therapeutic efficacy to block cocaine self-administration and dependence.

2. Rat Social Interaction Test

INTRODUCTION

One major therapeutic drawback to the use of benzodiazepine anxiolytics is the development of tolerance to the drugs and the induction of a withdrawal syndrome on cessation of treatment, where symptoms of anxiety (e.g. irritability, tension, restlessness, foreboding, tremor, headache, sweating and insomnia) pose a particular difficulty in the majority of patients (Marks 1985) . In the present study the effects of test compound on withdrawal from diazepam were studied using the rat social interaction test of anxiety (File, 1985) . In this test low light familiar conditions were used to facilitate the observation of anxiogenic responses.

METHODS

Male CD rats (Charles River) were housed in groups of 6 under a 12h light (lights on 7.00 a.m.) cycle with free access to food (standard rat chow) and water in a room adjacent to the testing room. They were orally dosed for 14 days with vehicle or diazepam (40 mg/kg) twice daily. On day 11 rats were individually housed in the same room and on days 13 and 14 were placed in the social interaction chamber (made of black perspex 54 cm x 37 cm x 26 cm with a transparent perspex front side and no lid, floor divided into 24 squares by white lines) under red light for 10 mins. On day 15, one day after the last dose of diazepam or vehicle, they were administered vehicle or test compound (0.01 or 0.1 mg/kg p.o.) 12h and 30 min pretest and placed with an unfamiliar weight matched (±30g) pair mate into the social interaction chamber in an adjacent room. Active social interaction (sniffing, grooming, following, mounting, boxing, biting, crawling over/under) and locomotion (no. of squares entered) was scored by remote video monitoring by a 'blind' observer over the next 15 mins. The rats were then removed and the box carefully wiped with a damp cloth before testing of a subsequent pair of rats. Daily body weight change was monitored for each rat over the whole 15 day experimental period.

Drugs; Diazepam and test compound were ground in a pestle and mortar and suspended (dissolved test compound) in 1% methyl cellulose. All drug doses refer to free base and were given in a volume of 1 ml/kg p.o.

STATISTICS

The ability of test compound to reverse the effects of withdrawal from chronic diazepam was assessed by 2 way ANOVA and Newman Keul's test. Effect of withdrawal from chronic diazepam (40 mq/kq) and Compound substitution.

One day withdrawal from chronic diazepam (40 mg/kg p.o., 5 b.i.d. x 14 days, vehicle day 15 12h and 30 min pretest p.o.) significantly suppressed social behaviours (Table) in the social interaction test under low light familiar conditions, but had no effect on locomotion (Table) . Administration of test compound (the Compound, hydrochloride 10 salt) (0.01 or 0.1 mg/kg p.o.) to chronic diazepam (40 mg/kg) withdrawn rats 12h and 30 min pretest significantly reversed the deficit in social interaction scores (Table) . None of the above treatments affected locomotion (Table) .

15 DISCUSSION

Withdrawal from chronic diazepam treatment lowered social interaction of rats but not locomotion during the test. This is consistent with the induction of anxiety (File

201985) . This anxiogenic-like response is similar to that reported by Costall et al (1989) using the same anxiety model. Costall et al (1989) also reported an anxiogenic response to diazepam withdrawal in the mouse light/dark box test of anxiety. These results in animal tests may model

25 the clinical anxiogenic response to cessation of prolonged benzodiazepine treatment (Marks 1985) . The ability of the Compound to reverse the anxiogenic effects of chronic diazepam withdrawal suggests that the Compound has potential therapeutic efficacy in the treatment of anxious patients

30 particularly those withdrawn from long term (or short) treatment with benzodiazepines. REFERENCES

Costall, B., Jones, B.J., Kelly, M.E., Naylor, R.J., Onaivi, E.S. and Tyers, M.B., (1989) Ondansetron inhibits a behavioural consequence of withdrawal from drugs of abuse. Pharmacol. Biochem. Behav., 36, 339-344.

File, S.E. (1985) Animal models for predicting clinical efficacy of anxiolytic drugs: social behaviour. Neuropsychobiology 13, 55-62.

Marks, J., (1985) Description of the benzodiazepine withdrawal reaction. In : Marks. J., ed. The benzodiazepines, use, overuse, misuse, abuse. Lancaster: MTP Press Ltd; pp 33-38.

Table :

Effect of the Compound, hydrochloride salt (0.01 or 0.1 mg/kg) or vehicle (p.o. on day 15, 12h and 30 min pretest) on the behavioural response to withdrawal from chronic diazepam (40mg/kg p.o., b.i.d., x 14 days) in the rat social interaction test.

Significantly different from vehicle + vehicle treated group ** p<0.01

Significantly different from diazepam + vehicle treated group + p<0.05 ++ p<0.01 by Dunnett's test following significant 1 way ANOVA

Claims

1. A method for the relief or prevention of a withdrawal syndrome resulting from addiction to a drug or substance of abuse and/or for the suppression of dependence on drugs or substances of abuse in mammals including humans, which method comprises administering an effective, non-toxic amount of endo-N-(8-methyl-8-azabicyclo [3.2.1]oct-3-yl)- 2,3-dihydro-3,3-dimethylindole-l-carboxamide or a pharmaceutically acceptable salt or solvate thereof to the mammal in need of such treatment.

2. A method according to claim 1 wherein the drug or substance of abuse is cocaine.

3. A method according to claim 1 wherein the drug or substance of abuse is a benzodiazepine.

4. Use of endo-N-(8-methyl-8-azabicyclo [3.2.1]oct-3-yl)- 2,3-dihydro-3,3-dimethylindole-l-carboxamide or a pharmaceutically acceptable salt or solvate thereof in the preparation of a medicament for the relief or prevention of a withdrawal syndrome resulting from addiction to a drug or substance of abuse and/or for the suppression of dependence on drugs or substances of abuse in mammals including humans.

5. Use according to claim 4 wherein the drug or substance of abuse is cocaine.

6. Use according to claim 4 wherein the drug or substance of abuse is a benzodiazepine.

7. A pharmaceutical composition for the relief or prevention of a withdrawal syndrome resulting from addiction to a drug or substance of abuse and/or for the suppression of dependence on drugs or substances of abuse in mammals including humans, which comprises an effective amount of endo-N-(8-methyl-8-azabicyclo [3.2.1]oct-3-yl)-2,3-dihydro- 3,3-dimethylindole-l-carboxamide or a pharmaceutically acceptable salt or solvate thereof and a pharmaceutical carrier.

8. A composition according to claim 7 wherein the drug or substance of abuse is cocaine.

9. A composition according to claim 7 wherein the drug or substance of abuse is a benzodiazepine.