My Research

Six experienced cocaine smokers (two men, four women) participated in an inpatient study to compare self-administration of smoked cocaine when either a $5 money or merchandise voucher was available as an alternative reinforcer. A six-trial choice procedure was used, with sessions consisting of (1) one sample trial, where participants received the cocaine dose and the alternative reinforcer available that day, and (2) five choice trials, where participants chose between the available cocaine dose and the alternative reinforcer. There were eight sessions: in separate sessions, each dose of cocaine (0, 12, 25, 50 mg) was paired with a money voucher and with a merchandise voucher. The choice to self-administer cocaine significantly increased with escalating cocaine doses, and significantly less cocaine was self-administered when money vouchers were available as compared to merchandise vouchers. These data demonstrate that money vouchers are a more effective alternative reinforcer than merchandise vouchers in cocaine abusers.

Modafinil has been reported to reduce cocaine use in a clinical sample of infrequent users (2 days/week), but the effects of modafinil on cocaine self-administration in the laboratory have not been studied. The present study investigated the effects of modafinil maintenance on cocaine self-administration by frequent users (4 days/week) under controlled laboratory conditions. During this 48-day double-blind, crossover design study, the effects of modafinil maintenance (0, 200, and 400 mg/day) on response to smoked cocaine (0, 12, 25, and 50 mg) were examined in nontreatment-seeking cocaine-dependent individuals (n=8). Cocaine significantly increased self-administration, subjective-effect ratings, and cardiovascular measures; modafinil at both doses (200 and 400 mg/day) markedly attenuated these effects. These findings agree with data from previous human laboratory and clinical investigations of modafinil as a potential cocaine abuse treatment medication. Thus, our data support the potential of modafinil as a pharmacotherapy for cocaine dependence.

Intranasal methamphetamine abuse has increased dramatically in the past decade, yet only one published study has investigated its acute effects under controlled laboratory conditions. Thus, the current study examined the effects of single-dose intranasal methamphetamine administration on a broad range of behavioral and physiological measures. Eleven nontreatment-seeking methamphetamine abusers (two females, nine males) completed this four-session, in-patient, within-participant, double-blind study. During each session, one of four intranasal methamphetamine doses (0, 12, 25, and 50 mg/70 kg) was administered and methamphetamine plasma concentrations, cardiovascular, subjective, and psychomotor/cognitive performance effects were assessed before drug administration and repeatedly thereafter. Following drug administration, methamphetamine plasma concentrations systematically increased for 4 h postdrug administration then declined. Methamphetamine dose dependently increased cardiovascular measures and ‘positive’ subjective effects, with peaks occurring approximately 5–15 min after drug administration, when plasma levels were still ascending. In addition, cognitive performance on less complicated tasks was improved by all active methamphetamine doses, whereas performance on more complicated tasks was improved only by the intermediate doses (12 and 25 mg). These results show that intranasal methamphetamine produced predictable effects on multiple behavioral and physiological measures before peak plasma levels were observed. Of interest is the dissociation between methamphetamine plasma concentrations with cardiovascular measures and positive subjective effects, which might have important implications for potential toxicity after repeated doses.

RATIONALE:

Most reports of the effects of methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA) on speech have been anecdotal.
OBJECTIVES:

The current study used a within-participant design to assess the effects of methamphetamine and MDMA on speech.
MATERIALS AND METHODS:

Eleven recreational users of amphetamines completed this inpatient, within-participant, double-blind study, during which they received placebo, methamphetamine (20, 40 mg), and MDMA (100 mg) on separate days. Following drug administration, study participants described movies viewed the previous evening and completed mood scales.
RESULTS:

Methamphetamine increased quantity of speech, fluency, and self-ratings of talkativeness and alertness, while it decreased the average duration of nonjuncture unfilled pauses. MDMA decreased fluency and increased self-ratings of inability to concentrate. To determine if methamphetamine- and MDMA-related effects were perceptible, undergraduates listened to the participants’ movie descriptions and rated their coherence and the speaker’s mood. Following methamphetamine, descriptions were judged to be more coherent and focused than they were following MDMA.
CONCLUSIONS:

Methamphetamine improved verbal fluency and MDMA adversely affected fluency. This pattern of effects is consistent with the effects of these drugs on functioning in other cognitive domains. In general, methamphetamine effects on speech were inconsistent with effects popularly attributed to this drug, while MDMA-related effects were in agreement with some anecdotal reports and discordant with others.

Although the ability to perform complex cognitive operations is assumed to be impaired following acute marijuana smoking, complex cognitive performance after acute marijuana use has not been adequately assessed under experimental conditions. In the present study, we used a within-participant double-blind design to evaluate the effects acute marijuana smoking on complex cognitive performance in experienced marijuana smokers. Eighteen healthy research volunteers (8 females, 10 males), averaging 24 marijuana cigarettes per week, completed this three-session outpatient study; sessions were separated by at least 72-hrs. During sessions, participants completed baseline computerized cognitive tasks, smoked a single marijuana cigarette (0%, 1.8%, or 3.9% Δ9-THC w/w), and completed additional cognitive tasks. Blood pressure, heart rate, and subjective effects were also assessed throughout sessions. Marijuana cigarettes were administered in a double-blind fashion and the sequence of Δ9-THC concentration order was balanced across participants. Although marijuana significantly increased the number of premature responses and the time participants required to complete several tasks, it had no effect on accuracy on measures of cognitive flexibility, mental calculation, and reasoning. Additionally, heart rate and several subjective-effect ratings (e.g., “Good Drug Effect,” “High,” “Mellow”) were significantly increased in a Δ9-THC concentration-dependent manner. These data demonstrate that acute marijuana smoking produced minimal effects on complex cognitive task performance in experienced marijuana users.

Rationale

Despite their chemical similarities, methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA) produce differing neurochemical and behavioral responses in animals. In humans, individual studies of methamphetamine and MDMA indicate that the drugs engender overlapping and divergent effects; there are only limited data comparing the two drugs in the same individuals.
Objectives

This study examined the effects of methamphetamine and MDMA using a within-subject design.
Methods

Eleven adult volunteers completed this 13-day residential laboratory study, which consisted of four 3-day blocks of sessions. On the first day of each block, participants received oral methamphetamine (20, 40 mg), MDMA (100 mg), or placebo. Drug plasma concentrations, cardiovascular, subjective, and cognitive/psychomotor performance effects were assessed before drug administration and after. Food intake and sleep were also assessed. On subsequent days of each block, placebo was administered and residual effects were assessed.
Results

Acutely, both drugs increased cardiovascular measures and “positive” subjective effects and decreased food intake. In addition, when asked to identify each drug, participants had difficulty distinguishing between the amphetamines. The drugs also produced divergent effects: methamphetamine improved performance and disrupted sleep, while MDMA increased “negative” subjective-effect ratings. Few residual drug effects were noted for either drug.
Conclusions

It is possible that the differences observed could explain the differential public perception and abuse potential associated with these amphetamines. Alternatively, the route of administration by which the drugs are used recreationally might account for the many of the effects attributed to these drugs (i.e., MDMA is primarily used orally, whereas methamphetamine is used by routes associated with higher abuse potential).

Background

Sub-anesthetic ketamine infusions may benefit a variety of psychiatric disorders, including addiction. Though ketamine engenders transient alterations in consciousness, it is not known whether these alterations influence efficacy. This analysis evaluates the mystical-type effects of ketamine, which may have therapeutic potential according to prior research, and assesses whether these effects mediate improvements in dependence-related deficits, 24 h postinfusion.
Methods

Eight cocaine dependent individuals completed this double-blind, randomized, inpatient study. Three counter-balanced infusions separated by 48 h were received: lorazepam (2 mg) and two doses of ketamine (0.41 mg/kg and 0.71 mg/kg, with the former dose always preceding the latter). Infusions were followed within 15 min by measures of dissociation (Clinician Administered Dissociative Symptoms Scale: CADSS) and mystical-type effects (adapted from Hood’s Mysticism Scale: HMS). At baseline and 24 h postinfusion, participants underwent assessments of motivation to stop cocaine (University of Rhode Island Change Assessment) and cue-induced craving (by visual analogue scale for cocaine craving during cue exposure).
Results

Ketamine led to significantly greater acute mystical-type effects (by HMS) relative to the active control lorazepam; ketamine 0.71 mg/kg was associated with significantly higher HMS scores than was the 0.41 mg/kg dose. HMS score, but not CADSS score, was found to mediate the effect of ketamine on motivation to quit cocaine 24 h postinfusion.
Conclusions

These findings suggest that psychological mechanisms may be involved in some of the anti-addiction benefits resulting from ketamine. Future research can evaluate whether the psychoactive effects of ketamine influence improvements in larger samples.