Relative bioavailability of DL-oxyfedrine HCl after single-dose oral administration of tablets as compared to...

The pharmacokinetics and comparative bioavailability of oxyfedrine after single-dose oral administration of oxyfedrine*HCl tablets in comparison to an equimolar aqueous solution of oxyfedrine*HCl were investigated in 12 healthy male subjects. Six of them received 96 mg DL-oxyfedrine*HCl as tablets and solution and the remaining 6 subjects received 16 mg DL-oxyfedrine*HCl as tablets and solution in a randomized cross-over design. For evaluation of the relative bioavailability of the tablet formulation, the main metabolite norephedrine (expressed as hydrochloride) was analyzed in plasma for all 12 subjects. Furthermore, for determination of the parent drug, samples of whole blood were analyzed for DL-oxyfedrine*HCl. Relevant concentrations of the parent drug were found only in the high dosage group. There was no evidence of dose-linearity referring to AUC and Cmax of norephedrine between 16-mg and 96-mg doses of DL-oxyfedrine*HCl. The relative bioavailability of the tablet formulation after administration of 16 mg DL-oxyfedrine*HCl, based on the metabolite norephedrine*HCl was for AUC: 85.37% within a 90% confidence interval of 69.29-105.17% and for Cmax: 78.79% within a 90% confidence interval of 59.19-104.90%. The figures for the 96 mg dose strength were: AUC: 107.85% (90.06-129.15%) and for Cmax: 74.74% (62.48-89.42%).