A nicotine antagonist, mecamylamine, reduces cue-induced cocaine craving in cocaine-dependent subjects

We have previously shown that nicotine enhances cue-induced cocaine craving. In the present study, the effects of a nicotine antagonist, mecamylamine, on cue-induced cocaine craving were investigated. Twenty-three cocaine-dependent patients, all cigarette smokers, were randomly assigned to mecamylamine (2.5 mg tablet) or placebo in a single-dose, placebo-controlled, crossover, double-blind study. Craving and anxiety were measured before and after cocaine cues with visual analog scales for desire to use cocaine and mood. Skin conductance, skin temperature and heart rate were recorded before and during cocaine cues. Following exposure to cocaine cues, all patients reported an increase in cocaine craving and anxiety relative to the precue measures. Cue exposure also produced an increase in skin conductance and decrease in skin temperature. The cue-induced increase in cocaine craving was reduced, while the cue-induced skin conductance and temperature responses were unaffected, by mecamylamine. These findings show that cue-induced cocaine craving is attenuated by mecamylamine. Further study on the use of mecamylamine in relapse prevention programs are suggested.

An acute dose of nicotine enhances cue-induced cocaine craving

The present study examined whether the active component in tobacco, nicotine, can modulate cocaine craving in patients with a history of smoking crack cocaine when exposed to crack cocaine related environmental cues. Twenty patients, all cigarette smokers, were randomly assigned to nicotine (two 22 mg transdermal patches) or placebo in a single-dose, placebo-controlled, crossover, double-blind study. Craving and anxiety were measured before and after cocaine cues with visual analog scales for desire to use cocaine and mood. Skin conductance and skin temperature were recorded before and during cocaine cues. Following exposure to cocaine cues, all patients reported an increase in cocaine craving and anxiety relative to the pre-cue measures. Cue exposure also produced an increase in skin conductance and decrease in skin temperature. The cue-induced increase in cocaine craving was strongly enhanced by nicotine, while the increase in anxiety was slightly augmented. Cue-induced skin conductance and temperature responses were unaffected by nicotine. These findings show that cue-induced cocaine craving is enhanced by nicotine. This occurred in the absence of any tobacco smoking-related cues, suggesting that nicotine may have direct psychopharmacological effects on conditioned cocaine craving.

Haloperidol antagonism of cue-elicited cocaine craving

BACKGROUND

Studies of cocaine-dependent subjects have shown that re-exposure to environmental cues previously associated with cocaine use produces a strong conditioned response characterised by autonomic hyperarousal and increases in subjective measures of cocaine craving.

METHODS

To evaluate the role of dopamine release by such cues, 20 cocaine-dependent inpatients were randomised in a single-dose, crossover, placebo-controlled design, to haloperidol (4 mg by mouth) and placebo. Plasma homovanillic acid (HVA, a dopamine metabolite), adrenocorticotropic hormone (ACTH), and cortisol were assayed before and after cue exposure. Craving and anxiety were measured before and after cues with visual analogue scales for desire to use cocaine now and for mood changes.

FINDINGS

Cocaine cues significantly increased anxiety, ACTH, cortisol, and HVA. Increases in anxiety and craving resulting from cue exposure were significantly antagonised by pretreatment with haloperidol.

INTERPRETATION

It has long been hypothesised that increases in extracellular concentrations of dopamine mediate the acute reinforcing effects of cocaine. Our data suggest that dopamine release may also mediate some of the conditioned responses to cocaine cues.