Clinicians who use blood-thinner pills (oral anticoagulants) to treat patients with atrial fibrillation (AF) are turning to the recently approved drug, dabigatran, rather than the 60-year-old oral anticoagulant warfarin, according to a new study. Historically, heart patients with AF have had a fivefold increased risk of stroke, which is reduced by two-thirds by anticoagulant therapy.
Warfarin, an antagonist of the clotting factor vitamin K, has been for decades the most widely used drug for preventing dangerous blood clots. It is relatively inexpensive, but requires constant testing to ensure that the anticoagulant level remains within a safe range, that is, the blood does not become so thin that it causes internal bleeding, but thinned sufficiently to prevent blood clots. In addition, a number of other important medications can interact with warfarin to reduce its effectiveness.
Dabigatran, which was approved by the U.S. Food and Drug Administration for treatment of AF in October 2010, does not need routine monitoring and interacts with fewer drugs. However, its retail price is 15 times that of warfarin. The researchers wanted to know how usage of the two blood thinners has changed since the approval of dabigatran.
Using a quarterly survey of physicians’ diagnoses and medications prescribed, they found that from the first quarter of 2007 through the fourth quarter of 2011, visits involving prescriptions for warfarin declined from 2.12 million to 1.56 million per quarter. Dabigatran visits were a mere 0.06 million before the fourth quarter of 2010 and rose to 0.36 million by the fourth quarter of 2011. In contrast, treatment of AF accounted for 42 percent of warfarin visits in the fourth quarter of 2010 compared with 92 percent for dabigatran (the remaining 8 percent being visits for hypertensive heart disease). By the fourth quarter of 2011, AF visits accounted for 39 percent of warfarin prescriptions, but only 63 percent of dabigatran prescriptions—despite AF remaining the only approved indication for the new drug’s use.
The findings were based on diagnostic and prescribing data from the National Disease and Therapeutic Index and prescription expenditures from the National Prescription Audit. The study was funded in part by AHRQ (HS17567).
More details are in "National trends in oral anticoagulant use in the United States, 2007–2011," by Kate Kirley, M.D., Dima M. Qato, Pharm.D., M.P.H., Ph.D., Rachel Kornfield, M.A., and others in the September 2012 Circulation. Cardiovascular Quality and Outcomes 5(5), pp. 615–621.