Therapeutic implications of drug interactions with acetaminophen and aspirin.

Only drug-drug interactions that are believed clinically important and that are primarily pharmacokinetic in nature are discussed in this article. Drugs reported to interact with aspirin are oral anticoagulants, methotrexate, probenecid, and sulfinpyrazone; those that are believed to interact with acetaminophen are propantheline bromide, narcotics, and metoclopramide hydrochloride, as well as food (carbohydrates). Ethyl alcohol, ammonium chloride, antacids, oral antidiabetic agents, corticosteroids, and heparin sodium probably interact with aspirin. Fenoprofen calcium, gold sodium thiomalate, indomethacin, naproxen, penicillin, phenylbutazone, phenytoin sodium, and spironolactone may also cause such interactions. Ethyl alcohol, beta-adrenergic blockers, oral anticoagulants, chlorpromazine hydrochloride, and miscellaneous mutual toxicities may cause interactions with acetaminophen. The concomitant use of drugs that are believed to interact importantly with either aspirin or acetaminophen should be avoided when designing a treatment regimen. The remaining agents discussed here (of doubtful importance in man) demand careful monitoring in difficult clinical situations and must be submitted to further controlled studies.