Pharmacokinetics of tramadol and its three main metabolites in healthy male and female volunteers.

By using a high-performance liquid chromatography method, the pharmacokinetics of the tramadol (T) and its three main metabolites, O-desmethyltramadol (M1), N-desmethyltramadol (M2) and O,N-didesmethyltramadol (M5) was studied in healthy male and female Iranian volunteers after oral administration of two 50 mg tramadol hydrochloride tablets. The related pharmacokinetic parameters such as C(max), T(max), AUC((0-t)), AUC((0-infinity)), T(1/2) and Cl/F were calculated and compared between the two genders. No significant differences were found in the systemic exposure and pharmacokinetic of tramadol, M1 and M2 while there were significant differences in AUCs of M5 in the two genders. It was concluded that to get a more accurate result, the gender dependency of T and its metabolites might be studied in specific phenotypes.