Kinetics of pharmacologic response to cocaine

Cocaine plasma concentration-response-time data obtained from the literature were analyzed by pharmacokinetic methods. The plasma concentration-time data yield an elimination half-life of approximately 1 hour and the data suggest that only about 20% of an oral dose of cocaine is absorbed intact into the systemic circulation. Response, as assessed by means of a relative 'high' rating scale, declined linearly with time as predicted by theory. The rate of decline of response was found to be 0.0221 'high'/min. The rate of decline of response is a function of the apparent first-order elimination rate constant (K) of the drug and the slope of the response-log plasma concentration curve (m). A value for m of 4.2 'high' was calculated from the response-time data which agreed well with a value of 3.9 'high' for m determined from the slope of the response-log plasma concentration curve.