LOW-DOSE VITAMIN K DECREASES INR FLUCTUATION
Patients who experiencelarge fluctuations in theirinternational normalized ratio(INR) measurement may benefitfrom supplementationwith low-dose vitamin K. Asmall study of 8 highly motivated,adherent patients whowere experiencing significantchanges in their INR for no identifiable reasonbegan taking 100 μg of vitamin K daily,similar to the usual daily vitamin K intakein the United States (60-90 μg).They beganthis therapy with the knowledge of theiranticoagulation provider, and only whentheir INR was elevated or not significantlybelow their INR target.
The absolute number of INRs increasedin range from 18% to 42%after supplementation. Onlyone patient failed to achievebetter INR control. (Thispatient had lupus anticoagulant,which is known tointerfere with INR measurements.)The authors concludedthat these resultswarrant further study of the use of vitaminK for INR stabilization.
Patients who are selected for this therapyneed to be monitored very carefully,as the INR may drop substantially duringthe initial 1 to 2 weeks of treatment.Patients should never begin vitamin Ksupplementation without the approval oftheir anticoagulation provider.
Dr. Garrett is a clinical pharmacistpractitioner at Cornerstone HealthCare in High Point, NC.