Methods: Twelve healthy male subjects were given individually adjusted doses of warfarin to reduce prothrombin time (Quick's method) to a value of about 30–40% of the normal range within the first 8 days. Then, the individual maintenance dose, given in the morning, was maintained until day 15. On study days 11–15, voglibose was co-administered per os in a dose of 5 mg t.i.d. The prothrombin time was determined on days 10 and 11 (reference) and on days 15 and 16 (test), and the steady-state pharmacokinetic characteristics of the warfarin enantiomers were determined on days 10 (reference) and 15 (test). The ratios test/reference were evaluated according to bioequivalence criteria.

Results: The equivalence ratio (test/reference) for the pharmacodynamic parameter prothrombin time was 0.97 and for the pharmacokinetic characteristics AUC_{0–24 h,τ,ss}: S-(−)-warfarin, 1.05; R-(+)-warfarin, 1.01; and C_max,ss: S-(−)-warfarin, 1.08; R-(+)-warfarin, 1.04. All parameters were within the predetermined accepted range of 0.7–1.43 (pharmacodynamics) or 0.8–1.25 (pharmacokinetics), thus fulfilling equivalence criteria.

Conclusions: Voglibose modified neither the pharmacodynamics nor the pharmacokinetics of warfarin under steady-state conditions. Concomitant treatment was well tolerated and has been proven to be safe for further clinical use.