Lack of pharmacodynamic interaction between pentoxifylline and warfarin in the rat.

Pentoxifylline is a new hemorrheologic agent which decreases platelet aggregation and reduces fibrinogen levels. Its ability to affect the coagulation cascade was studied in rats with and without the coadministration of warfarin. There was no significant difference between the prothrombin time ratio (PTR) of the warfarin group (1.51 +/- 0.38) and the combination drug group (1.47 +/- 0.30) at 6 hours. Likewise, there was no significant difference between the PTR of the control group (1.09 +/- 0.07) and the group administered pentoxifylline alone (1.05 +/- 0.06). Although the mechanisms of action of the two drugs may overlap, the pharmacodynamic activity of warfarin was not significantly altered when pentoxifylline was coadministered.