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Possible Effect of Refrigeration of Warfarin on the International Normalized Ratio
Author(s) -
Sharp Randall P.,
Havrda Dawn E.
Publication year - 2002
Publication title -
pharmacotherapy: the journal of human pharmacology and drug therapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.227
H-Index - 109
eISSN - 1875-9114
pISSN - 0277-0008
DOI - 10.1592/phco.22.1.102.33509
Subject(s) - warfarin , medicine , emergency medicine , anesthesia , atrial fibrillation
A 43‐year‐old African‐American woman taking warfarin for prevention of ischemic stroke experienced fluctuating international normalized ratio (INR) values over 8.5 months; no cause could be identified. After reading a pharmacy information sheet that accompanied a warfarin refill, she reported that she had been refrigerating her warfarin because her other drugs had been “sticking together.” She then was instructed to store her warfarin at room temperature. During the 8.5 months she had been refrigerating her warfarin, 80% of her INR values had been outside her goal range versus 37.5% during 9 months of storage at room temperature. A MEDLINE search and communication with the drug's manufacturer provided no information regarding storage of warfarin outside the temperature range of 59–86°F and resultant changes in potency of the drug. Because of potential fluctuation in anticoagulation control, patients should be reminded to store their warfarin at room temperature.