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Interaction of Ascorbic Acid and Warfarin

Edgar C. Smith, MD; Richard J. Skalski, MSc; Gilbert C. Johnson, MSc; G. Victor Rossi, PhD
JAMA. 1972;221(10):1166. doi:10.1001/jama.1972.03200230052025.
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To the Editor.—  Rosenthal (215:1671, 1971) described a patient, stabilized with warfarin sodium (Coumadin), whose prothrombin time was appreciably reduced during a period of self-administration of ascorbic acid (dose not reported). Subsequently, Hume et al (219:1479, 1972) noted that 1 gm of ascorbic acid administered daily for 14 days did not interfere with the effect of warfarin on coagulability (as monitored by the Thrombotest) in five patients receiving long-term therapy with warfarin for myocardial infarction.Our communication describes a case of unusual resistance to warfarin in a patient with acute thrombophlebitis who had been consuming approximately 16 gm of ascorbic acid per day. Laboratory studies with high doses of ascorbic acid administered orally in rabbits did not, however, reveal significant inhibition of the anticoagulant action of warfarin sodium.

Report of a Case.—  A 70-year-old woman had been treated at Presbyterian-University of Pennsylvania Medical Center for acute thrombophlebitis and was discharged


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