Warfarin therapy: Tips and tools for better control

Seek medical attention. Patients engaged in self-testing and monitoring also need to be aware of the importance of obtaining treatment for dangerously high or low INR levels and being alert to early indicators of bleeding or other significant adverse effects. Similarly, family physicians who care for such patients need to establish a system to ensure that these individuals are not lost to followup. Whether INR results are transmitted by fax, phone, or e-mail, a patient who leaves a message reporting an INR of 5.6, for example, requires a callback without delay.

Advise patients to watch for signs of warfarin-induced skin necrosis—a rare but serious complication of oral anticoagulant therapy characterized by dusky skin discoloration and pain, typically in an area with significant subcutaneous fat (eg, the breast or abdominal wall). Warfarin necrosis is estimated to occur in 0.01% to 0.1% of patients—primarily women—mostly in the first week of therapy.¹⁵ Other serious adverse effects are osteoporosis and purple toe syndrome.¹

Patients—and their family members—should also be advised that if the patient is hospitalized, it is critical to let the health care team know that he or she is taking warfarin. Patients should be encouraged to wear a medic alert bracelet, as well.

Warfarin’s effects can be reversed with vitamin K. (See “What to do when warfarin therapy goes too far,” J Fam Pract. 2009;58:346-352.) However, reversal may take 24 hours.⁷ In patients with life-threatening bleeding (eg, intracranial hemorrhage) and elevated INR, regardless of the magnitude of the elevation, INR should be normalized urgently with fresh frozen plasma, prothrombin complex concentrate, or recombinant factor VIIa supplemented with vitamin K10 mg by slow intravenous infusion.⁷

CORRESPONDENCE
Michael J. Schwartz, MD, 5 Sunnydale Circle, Swannanoa, NC 28778; ms112@columbia.edu