Pharmacokinetics and bioequivalence of tiropramide in healthy volunteers

Two formulations of tiropramide ((+/-)alpha-(benzoylamino)-4-[2-(diethylamino) ethoxy]-N,N-dipropyl-benzenepropanamide hydrochloride, CAS 55837-29-1), an antispasmodic agent, were orally administered to 16 healthy volunteers by the Latin cross-over design with the purpose of evaluating bioequivalence and pharmacokinetics of tiropramide. Tiropramide in human plasma was determined by a gas chromatography/nitrogen phosphorus detector. The detection limit of tiropramide was 5 ng/ml. Cmax values of test and reference formulations were 93.9 +/- 54.3 and 96.4 +/- 51.6 ng/ml, respectively. AUC0-->last and AUC0-->inf were 330.7 +/- 193.9 and 349.5 +/- 205.3 ng.h/ml, respectively, for the test formulation, 348.9 +/- 207.7 and 380.8 +/- 239.0 ng.h/ml, respectively, for the reference formulation. The terminal half-life was 2.34-2.61 h. Bioavailability differences for Cmax and AUC0-->last were -2.48% and -5.22%, respectively. Minimum detection differences were less than 20% for both Cmax and AUC0-->last. The 90% confidence limits of geometric mean values for logarithmically transformed Cmax and AUCs were within 0.8-1.25. Based on these results, the two formulations of tiropramide are considered to be bioequivalent.