Little is known about the acute effects of psychoactive drugs on impulsivity and decision making in humans. This study examined the effects of d-amphetamine (AMP; 10 and 20 mg; N = 20) and ethanol (EtOH; 0.2, 0.4, and 0.8 g/kg; N = 17) on the stop task, a putative measure of behavioral inhibition and impulsivity in healthy human volunteers. The stop task provides a measure of the reaction time (RT) needed to inhibit a response (Stop RT [SRT]), relative to the time taken to execute a simple response (Go RT [GRT]). Healthy volunteers performed the stop task before and after receiving one of the drugs. AMP decreased SRT-that is, improved inhibition-only in participants with slow baseline SRTs. EtOH increased SRTs-that is, impaired inhibition-at doses that did not affect CRTs. These results suggest that AMP and EtOH have specific and distinctive effects on the ability to inhibit responses. Impairment in the ability to inhibit responses is thought to reflect a certain form of impulsivity.

Impulsivity has been operationalized as a choice of an immediate smaller reward over a larger delayed or uncertain reward. This study examined a procedure that measures reward preference under these contingencies in psychiatric outpatients considered either at a high or low risk for engaging in impulsive behavior depending on their psychiatric diagnoses. The participants' rates of delay and uncertainty reward discounting were compared with their performances on a behavioral inhibition task and responses on a self-report personality impulsivity measure. The high-risk participants discounted delayed rewards more sharply and scored higher on the self-report impulsivity measure relative to the low-risk participants. Delay and uncertainty discounting were modestly correlated, but no other relationships were found between the other measures. Results from this study indicate that delay-discounting tasks may be sensitive to at least one form of impulsive behavior.

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Alternate-day buprenorphine dosing was compared to daily dosing in opioid-dependent outpatients and choice of alternate-day versus daily dosing was assessed. Four dosing schedules were presented in random order under blind and open dosing conditions. Subjects received two exposures to each dosing schedule. During daily dosing, subjects received maintenance doses every 24 h. During blind alternate-day dosing, subjects received double maintenance doses every 48 h; placebo was interposed on intervening days. During open alternate-day dosing, subjects received twice their maintenance dose on Monday, Wednesday and Friday and maintenance doses on Sunday. After completing two exposures to each dosing schedule, subjects chose either daily or alternate-day schedules each week for 1 month. Study participation was contingent on daily attendance and opioid abstinence. Ten subjects were exposed to the four conditions once. Seven subjects repeated these conditions and participated in the choice phase. The effects of daily versus alternate-day dosing were not influenced by blind or open dosing conditions. Subjects' ratings of withdrawal, "sick" and sedation were lower during daily than during alternate-day dosing, but the difference between treatments was small. Nonetheless, subjects still chose alternate-day dosing on 96% of occasions, suggesting that the subject-rated differences between dosing schedules were not influential. These results extend prior findings to open-dosing conditions, and replicate the safety and acceptability of alternate-day buprenorphine treatment. Choice of alternate-day buprenorphine administration underscores the procedure's clinical utility and potential use as a positive reinforcer to enhance opioid treatment.

These results suggest that buprenorphine may be administered safely every 72 h by tripling the maintenance dose, with only minimal withdrawal complaints. Importantly, this 72-h dosing may permit patients to attend clinic thrice weekly without the use of take-home doses.