Preclinical assessment of abuse liability of drugs.

Studies that are used in preclinical assessment of the liability of a drug to become an abuse problem are reviewed. These studies examine the capacity of a drug to produce physiological dependence or to function as a reinforcer. Studies that examine physiological dependence by assessing whether a drug reverses signs of withdrawal from a standard drug are rapid, reliable and inexpensive methods for determining if a drug produces dependence of a type similar to the standard. However, these techniques will not determine if the drug produces a unique type of dependence. Studies that examine whether a drug functions as a reinforcer have been predictive of whether a drug will be abused in human populations. Attempts to rank order drugs with respect to their efficacy as reinforcers, however, are not predictive of measures of extent of abuse in human populations. Since abuse of drugs in human populations is a function of societal variables in addition to pharmacological factors, it is unlikely that preclinical assessments will ever yield more than qualitative information on abuse liability of drugs.