JONATHAN LEOR, M.D.; DAVID LEVARTOWSKY, M.D.; CHARLOTTE SHARON, M.D.
To the editor: Nalidixic acid, the prototype of the quinolones family, is used extensively as an antimicrobial agent for urinary tract infections. The following case report suggests that nalidixic acid given to patients on long-term warfarin therapy can cause potentially dangerous over-anticoagulation. It is important to report this interaction due to the recent introduction of the new fluroquinolone agents structurally related to nalidixic acid.
A 71-year-old woman with mitral stenosis, chronic atrial fibrillation, and thromboembolic phenomena, began warfarin treatment 6 years ago. Her regular dose was between 2.5 to 5 mg/d. The prothrombin time was well controlled within the acceptable
LEOR J, LEVARTOWSKY D, SHARON C. Interaction Between Nalidixic Acid and Warfarin. Ann Intern Med. ;107:601. doi: 10.7326/0003-4819-107-4-601_2
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Published: Ann Intern Med. 1987;107(4):601.
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