Acute abstinence effects following smoked cocaine administration in humans.

Acute abstinence symptomatology following multiple deliveries of smoked cocaine was examined. Twelve crack cocaine users (male and female) participated in an inpatient study. Participants smoked 7 deliveries of cocaine on each of 4 experimental days, with each participant being exposed twice to 2 dose sizes of cocaine (0.40 vs. 0.07 mg/kg "placebo"). Symptoms of cocaine abstinence were measured for 6 hr following cocaine administration and again the following morning. Participants reported feeling increased craving, anxiety, and uncertainty 30 min after the 7th delivery of 0.40 mg/kg cocaine, when cocaine plasma levels were still on the descending curve. It is not clear whether these were true abstinence effects or were due to residual effects of cocaine. No significant differences were found at subsequent abstinence-assessment points. These data indicate that acute abstinence effects from smoked cocaine in a laboratory setting may be minimal.

Individual differences in the subjective response to smoked cocaine in humans.

The individual variables that determine the effects of cocaine in humans are not well understood. In this study, we examined the relationship between the subjective response to cocaine and selected individual variables in cocaine-dependent participants. A single 0.4-mg/kg dose of smoked cocaine was received by 75 smoked cocaine users. The variables associated with increased subjective response to cocaine were male sex, presence of alcohol use, higher baseline Beck Depression Inventory (BDI) scores, and duration of cocaine use. The change in heart rate and diastolic blood pressure in response to cocaine delivery were also positively associated with the subjective response to cocaine. In contrast, body weight, years of schooling, and the change in the heart rate with the expectation of cocaine delivery were associated with a diminished subjective response to cocaine. The importance of these variables in maintaining the cocaine use behavior needs to be studied further.

Characteristics of research volunteers for inpatient cocaine studies: focus on selection bias.

In order to investigate the selection bias of subjects for inpatient human cocaine studies, characteristics of 859 potential subjects were examined. Excluded subjects compared with accepted group were more likely to be single and male, currently use drugs other than cocaine, have a history of intravenous cocaine use, and have medical or mental health problems or physical complaints. Subjects who were accepted but did not participate, compared with participants, were likely to spend more money on cocaine. These results suggest that potential subjects who were accepted to our research studies may not accurately represent all potential subjects for several important subject characteristics.

Predictors of cardiovascular response to smoked cocaine in humans.

The purpose of this study was to examine the predictors of heart rate and blood pressure changes following cocaine administration. Sixty-two smoked cocaine users received a single 0.4 mg/kg dose of smoked cocaine. Male sex, African American race, higher body weight and current marijuana use predicted a greater cardiovascular response to cocaine. In contrast, higher baseline blood pressure, heart rate, amount and frequency of current cocaine use and presence of current cocaine snorting predicted a diminished cardiovascular response to cocaine. Whether these predictors of the cardiovascular response to smoked cocaine in the laboratory also predict cardiovascular complications from long-term cocaine use needs to be studied further.

Sex and menstrual cycle differences in the subjective effects from smoked cocaine in humans.

To investigate sex and menstrual cycle effects in response to cocaine administration, data from existing studies were analyzed. First, responses to a single delivery of 0.4 mg/kg smoked cocaine were investigated. Women reported lower ratings for measures of paranoid/suspicious and heart racing/pounding than did men. In addition, women in the luteal phase reported diminished ratings for a measure of feel high than did both women in the follicular phase of the menstrual cycle and men. Second, responses to up to 6 deliveries of 0.4 mg/kg smoked cocaine were investigated. Women, compared with men, had lower ratings on feel high, heart racing/pounding, and feel stimulated. Results suggest that there are significant sex and menstrual phase differences in the subjective effects of cocaine.

Dissociation between subjective and behavioral responses after cocaine stimuli presentations.

This study was designed to explore the relationship between craving and cocaine-seeking behavior with the use of both subjective and behavioral measures. Five males and five females who have used crack at least two times a week for 6 months, and who reported using 0.5 g of crack within 24 h on at least one occasion, participated in an inpatient study. Subjects underwent a total of four experimental sessions, during which they were exposed to either neutral (Neutral Stimuli Condition) or cocaine-related (Cocaine Stimuli Condition) external and internal stimuli. Subjects were exposed to each stimuli condition twice, on separate days, in randomized order. External stimuli comprised neutral or cocaine-related videotapes and paraphernalia, and the internal stimulus was either a 5-mg ('placebo') or 0.4 mg/kg delivery of cocaine. At baseline and after each stimulus exposure, subjects completed a composite cocaine craving questionnaire. Subjects next worked on concurrently-available fixed-ratio tasks either for tokens that could be exchanged for money ($2) or for tokens that were exchangeable for deliveries of cocaine (0.4 mg/kg). The results show that subjects reported significantly greater cocaine craving after exposure to cocaine-related vs. neutral stimuli, indicating that craving for cocaine can be successfully modeled in a laboratory setting. However, this change in subjective response did not predict drug-seeking behavior. The number of cocaine tokens earned following exposure to the cocaine-related vs neutral stimuli was similar. These results suggest that in a laboratory setting, craving may be unrelated to cocaine-seeking behavior in non-treatment-seeking cocaine users.