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August 20, 1997

Loading Dose and Monitoring of Warfarin Therapy-Reply

Author Affiliations

Medical College of Wisconsin Milwaukee

JAMA. 1997;278(7):548. doi:10.1001/jama.1997.03550070040029

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The purpose of my article was to make a recommendation regarding the use of a loading dose of warfarin. There was no intent to make any recommendation regarding the frequency of monitoring the INR. The phrase "titrate the daily dose based on the INR" found in the conclusion is not meant to imply that the INR should be measured daily. The letter from Dr Portnoi makes a valid point. The pharmacodynamics of warfarin are such that daily monitoring of the INR is excessive in most cases. In selected patients at risk for bleeding, early measurement of the INR may identify the patient who is very sensitive to the effects of warfarin before the active clotting factors are fully inhibited. In most cases, Portnoi's recommendations make sense for the inpatient setting. In the outpatient setting, daily monitoring is usually impractical, and intervals of 3 to 7 days for initial monitoring may