Cocaine and metabolite elimination patterns in chronic cocaine users during cessation: plasma and saliva analysis

Several reports suggest a prolonged elimination of cocaine and metabolites after chronic use compared with single or occasional use. This study was designed to measure the half-lives of cocaine in plasma and saliva of individuals who consumed cocaine on a frequent basis. The disposition and elimination patterns of cocaine and metabolites in the body fluids of chronic high-dose cocaine users during acute cessation of use were investigated. Plasma and saliva specimens were collected over a 12-h period during cessation and analyzed by gas chromatography-mass spectrometry. Pharmacokinetic parameters were derived by noncompartmental analysis of plasma and saliva data. Results indicated a cocaine terminal T(1/2) of 3.8 h in plasma and 7.9 h in saliva. The terminal T(1/2) of benzoylecgonine was 6.6 h in plasma and 9.2 h in saliva. Compared with prior studies of acute low-dose cocaine administration, these findings suggest that cocaine's half-life is longer in active street users than in occasional users though the half-life of its main metabolite benzoylecgonine remains similar (as do cocaine saliva-to-plasma ratios). Thus, regular use of cocaine appears to alter the disposition and elimination of cocaine when compared to single or occasional use.