Warfarin Doses Often Miss the Mark

Posted by William on June 22, 2011

Despite the continuous medical care promised by nursing homes, many elderly residents with atrial fibrillation aren’t getting the right dose of warfarin. That’s the finding of a new study questioning whether prescriptions for the commonly used anti-clotting drug (or “blood thinner”) meet standard treatment guidelines for the half of atrial fibrillation patients over 75.

Doctors often prescribe warfarin for atrial fibrillation, a common condition in which the heart’s upper chambers flutter irregularly rather than pump; this problem can lead to stroke when clots form in slow-moving blood. At the right doses, warfarin cuts the chance of stroke by an average of two thirds. But too much of the drug poses a risk of dangerous bleeding, especially in the elderly – making accurate prescriptions essential.

The study focused on the medical records of 130 elderly nursing home residents from 30 facilities in Canada and the US, all of whom took warfarin for their atrial fibrillation. The researchers found that during the previous year the patients received too much warfarin 16 percent of the time and too little 45 percent of the time.

These results, published in the May 12 Archives of Internal Medicine, were consistent with an earlier survey of nursing home physicians that found more than a quarter underestimated how much warfarin to give their elderly patients.

Anyone taking warfarin, regardless of age or level of physical impairment, must have frequent blood tests for some, as often as weekly to make sure they’re getting the right dose. Nursing home residents or their caregivers should check on the frequency of their blood tests and confirm with their doctors that their dosage is correct.