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Interacting Drugs

OBJECT DRUGS

Anticoagulants, Oral:

PRECIPITANT DRUGS

Analgesics:


Comment:

Aspirin increases the risk of bleeding in anticoagulated patients due to inhibition of platelet function and gastric erosions. Large doses of aspirin (e.g. 3g/day or more) can increase the hypoprothrombinemic response. However, low (antiplatelet) doses of aspirin appear to increase primarily minor bleeding and the combination is used intentionally in many patients. In some patients, acetaminophen can increase the hypoprothrombinemic response to warfarin and probably other oral anticoagulants. In most cases the interaction is small, but in predisposed patients marked hypoprothrombinemia has been reported. It would be prudent to limit acetaminophen dosage to 2 g/day or less for no more than a few days, and to monitor the INR.


Class 2: Use Only if Benefit Felt to Outweigh Risk