Influence of vinpocetine on warfarin-induced inhibition of coagulation

The influence of 14 days of concomitant vinpocetine administration on prothrombin time prolongation of single 25 mg doses of warfarin was investigated. Eighteen male subjects were included in the study. They received 25 mg warfarin the first day. Prothrombin time, warfarin plasma levels and factor VII coagulation time were monitored on days 1-5. Ten mg vinpocetine was administered from day 6 to 24. Another single dose of 25 mg of warfarin was given a second time on day 20. AUC values of prothrombin time, warfarin plasma level and factor VII clotting time curves and appropriate Cmax and tmax plasma levels of days 20-24 were compared with those of days 1-5. The confidence interval limits of the ratio of AUC20-24/AUC1-5 of prothrombin time curves were within the limits of 0.8 and 1.2, so that the formal criteria of equivalent biological activity were met. However, a minute influence probably without clinical implication is likely since both point estimate as well as confidence interval limits were below 1.