Intravenous drug injection habits: drug users' self-reports versus researchers' perception

The present study was designed to obtain human data on the speed of intravenous (i.v.) injection of cocaine, heroin, and morphine as well as on the rate of onset of their subjective effects and their duration in order to improve the accuracy of animal and human experimental models of i.v. drug abuse. To that end, a questionnaire was submitted both to clients of a substitution therapy outpatient clinic and to members of the drug abuse research community. It was found that i.v. drug abusers injected cocaine, heroin, or morphine much faster and also experienced the drug effects much faster than assumed by the drug abuse researchers. The time course of the reemergence of craving was also greatly misjudged by the researchers. On the other hand, the i.v. drug users' self-reports were internally consistent and corresponded well to data obtained in several different human behavioral laboratories. Interestingly, more than half of the i.v. drug users reported that injection speed was not important when injecting cocaine (57%), heroin (72%) or morphine (73%) under conditions that guarantee a maximum effect, suggesting that the rate of the rise in the brain concentration of a drug of abuse is less important for its reinforcing effect and, thus, for its abuse liability, than previously assumed, at least within the time frame of an i.v. drug injection.