Human coffee drinking: manipulation of concentration and caffeine dose.

In a residential research ward coffee drinking was studied in 9 volunteer human subjects with histories of heavy coffee drinking. A series of five experiments was undertaken to characterize adlibitum coffee consumption and to investigate the effects of manipulating coffee concentration, caffeine dose per cup, and caffeine preloads prior to coffee drinking. Manipulations were double-blind and scheduled in randomized sequences across days. When cups of coffee were freely available, coffee drinking tended to be rather regularly spaced during the day with intercup intervals becoming progressively longer throughout the day; experimental manipulations showed that this lengthening of intercup intervals was not due to accumulating caffeine levels. Number of cups of coffee consumed was an inverted U-shaped function of both coffee concentration and caffeine dose per cup; however, coffee-concentration and dose-per-cup manipulations did not produce similar effects on other measures of coffee drinking (intercup interval, time to drink a cup, within-day distribution of cups). Caffeine preload produced dose-related decreases in number of cups consumed. As a whole, these experiments provide some limited evidence for both the suppressive and the reinforcing effects of caffeine on coffee consumption. Examination of total daily coffee and caffeine intake across experiments, however, provides no evidence for precise regulation (i.e., titration) of coffee or caffeine intake.     

Low-dose caffeine discrimination and self-reported mood effects in normal volunteers.

A caffeine versus placebo discrimination procedure was used to determine the lowest caffeine dose that could produce discrimination and self-reported mood effects in normal volunteers. During daily sessions under double-blind conditions, caffeine-abstinent subjects orally ingested a capsule containing 178 mg caffeine or placebo. Before beginning discrimination training, the compounds were identified to subjects by letter codes. Fifteen, 30, and 45 min after capsule ingestion, subjects guessed the capsule's letter code. Correct guesses at 45 min earned money. After each session, subjects received a supplementary capsule containing caffeine or placebo to ensure that, within each phase of the study, subjects received the same daily dose of caffeine equal to the training dose. Five of the 15 subjects acquired the caffeine versus placebo discrimination within the first 20 sessions (greater than or equal to 75% correct); 6 other subjects acquired the discrimination with additional training. Nine subjects who acquired the discrimination were subsequently trained at progressively lower caffeine doses. In general, the lowest dose to produce discrimination (greater than or equal to 75% correct) was also the lowest dose to produce self-reported mood effects: 4 subjects showed discrimination and self-reported mood effects at 100 mg caffeine, 2 at 56 mg, 1 at 32 mg, and 1 at 18 mg. One of these subjects also showed self-reported mood effects at 10 mg. The present study documents discriminative stimulus and self-reported mood effects of caffeine at doses below those previously shown to affect any behavior in normal volunteers.     

Effects of cocaine and alcohol, alone and in combination, on human learning and performance.

The acute effects of cocaine hydrochloride (4 to 96 mg/70 kg) and alcohol (0 to 1.0 g/kg), administered alone and in combination, were assessed in two experiments with human volunteers responding under a multiple schedule of repeated acquisition and performance of response chains. Subjects were intermittent users of cocaine and regular drinkers who were not cocaine or alcohol dependent. Alcohol was mixed with orange juice and ingested in six drinks within 30 min; cocaine was administered intranasally 45 min after completion of drinking. In each component of the multiple schedule, subjects completed response sequences using three keys of a numeric keypad. In the acquisition component, a new sequence was learned each session. In the performance component, the response sequence always remained the same. Results were consistent in both experiments, despite variations in the order in which the drugs were tested alone and in combination. Alcohol administered alone increased overall percentage of errors and decreased rates of responding in the acquisition component, whereas responding in the performance component generally was unaffected. Cocaine administered alone decreased rates of responding but did not affect accuracy of responding in the acquisition component, and enhanced accuracy of responding without affecting rates of responding in the performance component. The combined doses of cocaine and alcohol attenuated the effects observed with alcohol and cocaine alone. These results suggest that, under the conditions investigated in this study, (a) alcohol produces greater behavioral disruption than cocaine or cocaine-alcohol combinations, (b) cocaine and alcohol each attenuate effects of the other, and (c) such attenuation is most pronounced for cocaine attenuating the disruptive effects of alcohol.     

SEPARATE AND COMBINED EFFECTS OF METHYLPHENIDATE AND A BEHAVIORAL INTERVENTION ON DISRUPTIVE BEHAVIOR IN CHILDREN WITH MENTAL RETARDATION

We investigated the separate and combined effects of a behavioral intervention and methylphenidate (Ritalin®) on disruptive behavior and task engagement in 3 children with severe to profound mental retardation. The behavioral intervention involved differential reinforcement of appropriate behavior and guided compliance. All 3 children demonstrated decreased disruptive behavior and improved task engagement in response to the behavioral intervention. Two of the 3 children demonstrated similar improvement in response to methylphenidate. Although both interventions were highly effective for these 2 participants, the relative efficacy of the interventions varied between the 2 children. There was no evidence of an additive or synergistic effect of the two interventions, but the high efficacy of each intervention alone limited our ability to detect such effects.     

Ethical issues in research on preventing HIV infection among injecting drug users

The ethical issues in conducting research on preventing HIV infection are among the most complex of any area of human subjects research. This article is an update of a 1987 article that addressed potential conflicts between research design and ethics with respect to AIDS prevention among injecting drug users. The present article reviews current ethical issues that arise in the design and conduct of HIV/AIDS prevention research focused on injecting drug users. Disclaimer: The content of this publication is solely the responsibility of the authors and does not necessarily represent the views of the Beth Israel Medical Center or Johns Hopkins University.     

Patterns of drug use and criminal activities among latino arrestees in California: Treatment and policy implications

This study examined the patterns of drug use and criminal activities among Latino arrestees. The findings indicate that while the prevalence of drug use at time of arrest, and in the prior 12 months were significantly lower for Latinos compared to Whites and Blacks, drug use still is of concern for this ethnic group. Almost 50% of Latinos reported drug use in the last year, and more importantly, they were more likely to report using dangerous drugs such as cocaine, heroin, and PCP than any other ethnic group. These findings are even more alarming considering that, for the most part, Latino drug users were treatment-naive, and that less than half perceived a need for drug treatment. Regarding criminal activities, Latinos were less likely to have a history of prior arrests and to have been arrested in the year prior to the interview than any other ethnic group. Interestingly, those immigrants who have resided in the U.S. for less than 1 year were significantly more likely to have been charged with drug-related crimes. U.S. born Latinos were more likely to have been arrested for property crimes, while Central American immigrants were more likely than any other Latino group to have been arrested for violent and domestic violence crimes. Treatment and policy implications of these findings are discussed.     

Facilitation of human tobacco self-administration by ethanol: a behavioral analysis.

The effect of ethanol on the cigarette smoking of alcoholic subjects was studied in a residential laboratory. During daily 6-hr sessions, cigarettes were obtained either by request to the ward staff or by operation of a lever (fixed-ratio 5 or 10). In a mixed sequence across days, sessions involved ingestion of either vehicle (orange juice or vehicle plus ethanol (133.7 g). During ethanol sessions, the rate of cigarette smoking increased from 26% to 117% of vehicle levels. A series of control studies eliminated a number of potential behavorial mechanisms for the observed effect and indicated that the ethanol-induced increase in cigarette smoking occurred under a variety of experimental conditions: (1) when smoking could not occur concurrently with ethanol or vehicle consumption; (2) when subjects were not allowed to socialize; (3) when ingestion of ethanol or vehicle was scheduled for a number of consecutive days; (4) when various doses of ethanol were administered under blind conditions. In control experiments, weighing unsmoked tobacco and counting the number of puffs per cigarette indicated the effect was not due to smoking less of each cigarette. The effect was not limited to the experimental sessions alone, since total daily smoking was higher on ethanol days than vehicle days.     

Phencyclidine discrimination in the pigeon using color tracking under second-order schedules

Pigeons were trained to track different key colors, depending on whether they had been injected with phencyclidine or saline prior to the session. A second-order schedule was used to generate large numbers of responses prior to the initial food delivery. The procedure offers several advantages over traditional procedures for studying drug discrimination.     

Peer identification and empirical validation of problematic interpersonal situations of male drug addicts

The present research was concerned with identifying and validating the problematic interpersonal situations of male veteran drug addicts. In Study I, 20 addicts self-monitored the situations with which they had difficulty coping and their associated characteristics throughout a 2-week period. Fifty situations were obtained and then rewritten into specific interpersonal scenarios. In Study II, a second group of 36 addicts and a comparison group of 20 disabled veterans rated the commonality and difficulty of each scenario along seven-point scales. Univariate ANOVAs found that five scenarios received ratings greater than four on both scales and were associated with significantly higher ratings by the addicts. These preliminary scenarios may serve as role-play situations during social-skills assessment and training and may provide further information regarding the interpersonal determinants of relapse occasioned in the natural environment. The need for controlled comparison studies using behavioral measures and an overall improvement in the methodological rigor of research in the area is discussed.The authors acknowledge the editorial comments of Ted D. Nirenberg, Ph.D., on an earlier draft of this paper. Portions of these data were presented at the Fifth World Congress on Behavior Therapy, Washington, DC.     

OPIOID ABSTINENCE REINFORCEMENT DELAYS HEROIN LAPSE DURING BUPRENORPHINE DOSE TAPERING

A positive reinforcement contingency increased opioid abstinence during outpatient dose tapering (4, 2, then 0 mg/day during Weeks 1 through 3) in non‐treatment‐seeking heroin‐dependent volunteers who had been maintained on buprenorphine (8 mg/day) during an inpatient research protocol. The control group (n = 12) received $4.00 for completing assessments at each thrice‐weekly visit during dose tapering; 10 of 12 lapsed to heroin use 1 day after discharge. The abstinence reinforcement group (n = 10) received $30.00 for each consecutive opioid‐free urine sample; this significantly delayed heroin lapse (median, 15 days).