Clinical Pharmacokinetics of Lofexidine, the α 2-Adrenergic Receptor Agonist, in Opiate Addicts Plasma Using a Highly Sensitive Liquid Chromatography Tandem Mass Spectrometric Analysis

Objectives: The objective of this investigation was to characterize the pharmacokinetic profile of lofexidine. Lofexidine is an orally bioavailable α 2-adrenergic receptor agonist analogue of clonidine that acts centrally to suppress opiate withdrawal symptoms. Methods: During the detoxification period of a phase 3 placebo-controlled, randomized, double-blind trial, six subjects were entered in this preliminary pharmacokinetic study. Results: Pharmacokinetic analysis of plasma samples collected during study day 7 indicated that Cmax was 3242 ± 917 ng/L. The mean trough levels between the study days were not significantly different (p >. 05), suggesting that the subjects were at steady-state. Conclusions: Although preliminary due to the limited number of subjects, these findings are the first to document lofexidine clinical pharmacokinetics in opiate addicts using a highly sensitive liquid chromatography tandem mass spectrometric analysis.