Bioequivalence and Bioavailability Forum

Dear Maverick
In principle, evaluation of bioequivalence should be based upon measured concentrations of the parent compound. The reason for this is that Cmax of a parent compound is usually more sensitive to detect differences between formulations in absorption rate than Cmax of a metabolite. So in your case the bioequivalence decision should be based on Pioglitazone alone. Pioglitazone is not a prodrug. Three of six metabolites are activ. Pioglitazone and the M-III metabolite have the same contribution to clinical efficacy, the M-IV metabolite is 6 times more potent, the efficacy of the M-II metabolite is less. If you can measure the M-III metabolite in the same run then I would suggest to do it but ensure that the statistics regarding the metabolites are descriptive and not conformativ.
I hope this helps
Kind regards
Dan