From time to time, I see a patient whose cardiologist has prescribed anticoagulation therapy with warfarin (Coumadin), but the doses vary, for example, 5 mg daily for five or six days, then a half tablet for the other day or two. That doesn’t make any sense to me. There are so many dosing options available that it seems it would be possible to prescribe the same dose daily. Are there any evidence-based reasons for varying the dose?
—David Lubin, MD, Tampa, Fla.
I’m sure many practitioners are as puzzled as Dr. Lubin by the variety of dosing schedules that cardiologists (and others) use to regulate their patients’ Coumadin regimens. To obtain the desired international normalized ratio (INR) (prothrombin time is no longer the preferred measurement), it is often not possible to “prescribe the same dose daily” as Dr. Lubin—and many others—would prefer. Only trial and error establishes the proper therapeutic range. But to play the devil’s advocate, I’m actually surprised by how frequently we can use regular schedules; in my experience, irregular dosing schedules are the exception, not the rule.
—Peter F. Cohn, MD (102-3)