LACK OF EFFECT OF TACRINE ADMINISTRATION ON THE ANTICOAGULANT ACTIVITY OF WARFARIN

The effect of tacrine administration on prothrombin time was studied i n 13 patients receiving prolonged warfarin therapy. After a 3-week bas eline period and 5 days of placebo administration, patients received 2 0 mg tacrine four rimes daily for 5 days. Prothrombin times were deter mined during baseline, daily before the morning doses of placebo and t acrine, and 14 days after the last tacrine dose (closeout). Mean (+/- SD) prothrombin times were 16.2 +/- 2.8 seconds at baseline, 15.1 +/- 2.6 seconds during the placebo phase, 15.8 +/- 3.6 seconds during the tacrine phase, and 15.3 +/- 3.6 seconds at closeout, indicating that t acrine has no effect on the anticoagulant activity of warfarin, Altera tion of warfarin dosage should not be required in patients receiving c oncurrent tacrine therapy.