The effects of repeated amphetamine exposure on multiple measures of human behavior

Two groups of three healthy adult male volunteers (n = 6) participated in 15-day residential studies. Each study day was divided into a private work period (1000 to 1630), during which subjects had access to four work tasks, and a social period (1700 to 2330), during which subjects had access to a number of recreational activities available under social or private conditions. Occasionally during the study, access to high-probability activities was made contingent upon participating in low-probability activities. Tobacco cigarettes and food were available throughout each day (0900 to 2330). Each subject received active and placebo d-amphetamine doses (0 or 10 mg/70 kg) twice daily during two, three-consecutive-day intervals. Active and placebo dose intervals were presented in an alternating fashion, with order of exposure counterbalanced between groups. Amphetamine consistently decreased food intake, improved accuracy of performance on some work tasks, and increased verbal interaction and cigarette smoking. No tolerance to these effects was observed. Increases in VAS ratings of dose "potency" and "liking," as well as "stimulated" and "anxious," and decreases in "sedated" were observed during initial amphetamine exposure, but tolerance to these effects developed rapidly. The simultaneous measurement of multiple dimensions of human behavior establishes a profile of amphetamine's effects which is useful for comparison with the behavioral profiles of other drugs, such as marijuana.