Residual effects of repeated cocaine smoking in humans.

A total of nine adult 'crack' cocaine users completed a protocol investigating changes in behavior on days following the self-administration of smoked cocaine. During self-administration sessions, participants could take up to six doses of smoked cocaine (50 mg; 25 mg for two participants). Both 2 and 3 day conditions were tested. During the 2 day condition, a cocaine self-administration session occurred in the afternoon and again in the evening on 2 consecutive days, while during the 3 day condition, self-administration sessions occurred twice a day-on 3 consecutive days. Participants reported greater cocaine craving (estimated using ratings of 'I want cocaine') and feeling more 'anxious,' 'confused,' 'of a good drug effect,' 'high,' 'sedated' and less 'friendly' the first day after using cocaine for 3 days compared to the first day after using cocaine for 2 days. Exposure to stimulus cues associated with smoked cocaine (e.g. participants preferred type of crack pipe) did not elicit cocaine craving or other behavioral changes after either 2 or 3 days of cocaine use. These data demonstrate that the cessation of heavy cocaine use under controlled laboratory conditions produced modest changes in mood and cocaine craving that were related to the length of the binge, and varied as a function of time since last cocaine use.