Preference procedures for testing the abuse liability of drugs in humans.

Drug preference procedures may be used to assess the abuse liability of drugs in human volunteers. These procedures usually measure subjects' choice of a drug versus a placebo, under controlled, double-blind conditions. Depending upon the conditions of the studies (e.g. subject population, environmental conditions of testing), drugs that are known to be abused are also preferred in these laboratory procedures. To assess the abuse liability of an unknown test drug, the frequency of choice of the test drug is compared to choice of a standard drug with known abuse potential: preference for the test drug, relative to the standard, is then taken as an indicator of its relative potential for abuse. A number of methodological variables must be considered when designing and interpreting choice studies, including the characteristics of the subjects, the range of doses tested, whether choices were spaced widely apart (e.g. one a day) or closely together (e.g. one immediately after another), and whether the study was conducted under controlled laboratory conditions or in the subjects' normal daily environments. The conditions for testing the abuse liability of an unknown compound must be selected based on the existing literature with similar, known drugs of abuse.