Conditions: Cocaine Dependence
Keywords: cocaine dependence psychopharmacology attentional bias risky decision making buspirone methylphenidate
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 50
Healthy volunteers: no

Brief summary:
Chronic cocaine use may produce disruption of neurotransmitter functions (including dopamine). This may in turn contribute to measurable dysfunction in important cognitive and behavioral processes. Stimulants that enhance dopamine (DA) function may help in treating cocaine dependence and improving behavioral function -- supporting the notion that these processes are related. An important step is to understand the subjective, physiological, and behavioral effects of potential medications for cocaine dependence.

DA-modulating drugs may be targets for pharmacotherapy for substance dependence, and particularly for stimulant drugs like cocaine, which disrupt normal DA function. Buspirone is currently the only available dopamine subtype 3 (DA3) approved for human administration, and is thus a viable investigational compound.

This project proposes to evaluate the DA-modulating effects of buspirone on behavioral deficiencies related to DA depletion. Accordingly, the project aims to characterize the effects of buspirone in individuals with cocaine dependence. Employing a daily dosing designs within an acute stimulant challenge (methylphenidate), the experiment will characterize the subjective effects, cardiovascular effects, and behavioral effects (attentional bias to drug cues and risky decision making). The primary hypotheses are that buspirone will attenuate the increases in subjective drug effects ("stimulated", "like drug") and behavioral effects (increases in attentional bias and risky decision making) that are produced by acute methylphenidate administration.

Detailed description:
Chronic cocaine use may produce disruption of monoamine systems (including dopamine). This may in turn contribute to measurable dysfunction in important cognitive and behavioral processes. Pharmacotherapy with stimulants that enhance dopamine (DA) function has shown efficacy in treating cocaine dependence and improving behavioral function -- supporting the notion that these processes are related. In the development of novel pharmacotherapies for cocaine dependence, an important step is a full characterization of the psychopharmacological properties of potential medications for cocaine dependence, including subjective, physiological, and behavioral effects. Selective medications may play a key role in the modulation of DA neurotransmission by enhancing DA receptor activation.

The D3 receptor is an autoreceptor that may function to control phasic DA activity and mediate sensitization of DA agonists, thus playing a role in conditioning of drugs of abuse like cocaine. Growing evidence suggests that D3 receptor antagonists may be targets for pharmacotherapy for substance dependence, and particularly for stimulant drugs like cocaine, which disrupt normal DA function. Importantly, administration of D3 antagonists may disrupt reactivity (attention) to drug cues and attenuate cue-induced craving. Buspirone is currently the only available D3 antagonist approved for human administration, and is thus a viable investigational compound.

This project proposes to evaluate the potential pharmacotherapeutic action of the D3 antagonist buspirone. The DA-modulating effects of buspirone may help with affective and behavioral deficiencies related to DA depletion. Accordingly, the project aims to characterize the psychopharmacology of buspirone in individuals with cocaine dependence. Employing chronic dosing designs within an acute stimulant challenge (methylphenidate), the experiment will be conducted using well-established psychopharmacological methods in order to characterize the shape and magnitude of chronic pretreatment-mediated change in the methylphenidate dose-response curve. Measures will include subjective effects, cardiovascular effects, and behavioral effects (attentional bias to drug cues and risky decision making). These data will compliment and provide valuable information to clinical trials using these agents to treat cocaine dependence.

Arms:
arm 1: \[week 1: Buspirone 30 mg twice a day (9am and 6pm) on Monday through Sunday; no Methylphenidate or Methylphenidate placebo\] \[week 2: Buspirone 45 mg twice a day (9am and 6pm) on Monday through Sunday; 0mg Methylphenidate (placebo) on Monday at 10am; Methylphenidate once a day (10am) on Wednesday and Friday, and on each of these 2 days the Methylphenidate dose will be different (15 mg, 30mg, 60 mg, or 0mg)\] \[week 3: Buspirone 45 mg twice a day (9am and 6pm) on Monday through Sunday; Methylphenidate once a day (10am) on Monday and Wednesday, and on each of these 2 days the Methylphenidate dose will be different (15 mg, 30mg, 60 mg, or 0mg)\] arm 2: \[week 1: Placebo for Buspirone twice a day (9am and 6pm) on Monday through Sunday; no Methylphenidate or Methylphenidate placebo\] \[week 2: Placebo for Buspirone twice a day (9am and 6pm) on Monday through Sunday; 0mg Methylphenidate (placebo for Methylphenidate) on Monday at 10am; Methylphenidate once a day (10am) on Wednesday and Friday, and on each of these 2 days the Methylphenidate dose will be different (15 mg, 30mg, 60 mg, or 0mg)\] \[week 3: Placebo for Buspirone twice a day (9am and 6pm) on Monday through Sunday; Methylphenidate once a day (10am) on Monday and Wednesday, and on each of these 2 days the Methylphenidate dose will be different (15 mg, 30mg, 60 mg, or 0mg)\]

Interventions: intervention 1: Buspirone intervention 2: Placebo for Buspirone intervention 3: Methylphenidate intervention 4: Placebo for Methylphenidate
Intervention descriptions: intervention 1: \[week 1: Buspirone 30 mg twice a day (9am and 6pm) on Monday through Sunday\] \[weeks 2-3: Buspirone 45 mg twice a day (9am and 6pm) on Monday through Sunday\] intervention 2: \[week 1: Placebo for Buspirone twice a day (9am and 6pm) on Monday through Sunday\] \[weeks 2-3: Placebo for Buspirone twice a day (9am and 6pm) on Monday through Sunday\] intervention 3: Methylphenidate serves as an acute stimulant challenge. \[week 1: no Methylphenidate or Methylphenidate placebo\] \[week 2: 0mg Methylphenidate (placebo for Methylphenidate) on Monday at 10am; Methylphenidate once a day (10am) on Wednesday and Friday, and on each of these 2 days the Methylphenidate dose will be different (15 mg, 30mg, 60 mg, or 0mg)\] \[week 3: Methylphenidate once a day (10am) on Monday and Wednesday, and on each of these 2 days the Methylphenidate dose will be different (15 mg, 30mg, 60 mg, or 0mg)\] intervention 4: \[week 1: no Methylphenidate or Methylphenidate placebo\] \[week 2: 0mg Methylphenidate (placebo for Methylphenidate) on Monday at 10am; Methylphenidate once a day (10am) on Wednesday and Friday, and on each of these 2 days the Methylphenidate dose will be different (15 mg, 30mg, 60 mg, or 0mg)\] \[week 3: Methylphenidate once a day (10am) on Monday and Wednesday, and on each of these 2 days the Methylphenidate dose will be different (15 mg, 30mg, 60 mg, or 0mg)\]

Protocol document: