Lack of Pharmacokinetic Interaction between Aspirin and Warfarin.

An open-label, randomized, two-phase crossover study was conducted on 36 healthy male volunteers to identify the effects of coadministration of aspirin (acetylsalicylic acid; ASA) and crystalline warfarin sodium (Coumadin((R))) on the elimination and disposition kinetics of ASA, salicylic acid (SA) and R- and S-warfarin enantiomers. Twenty-four subjects were administered single doses of 325 mg of ASA alone and in combination with 10 mg of crystalline warfarin sodium with a 1-week washout between ASA doses. ASA and SA pharmacokinetic parameters were determined after each dose.