Pharmacy Times, Volume 0, 0

A potential drug interaction existsbetween oral corticosteroids and warfarin,but there is limited evidence todocument it. A recent retrospectivereview of 387 medical records ofpatients followed in an anticoagulationclinic demonstrated an increase ininternational normalized ratio (INR) inthe majority of patients who had corticosteroidsadded to their warfarintherapy. Patients were included in thestudy if they were stable on warfarintherapy and were prescribed a shorttermcourse of corticosteroids. Theywere excluded if they were prescribedan antibiotic or any other medicationthat had a probable interaction withwarfarin at the same time the corticosteroidswere started. Thirty-two patientsmet the criteria. The primary outcomeassessed was the difference betweenpre-and poststeroid INR values.Secondary end points included bleedingevents, emergency department visits,hospitalizations, and warfarin dosemodifications. Ninety-seven percent ofthe 32 patients studied had changes intheir poststeroid INR value, 62.5% ofwhich were supratherapeutic. The INRchange was observed most commonlyafter 6 to 7 days of corticosteroid therapy.Overall, 16 patients required amodification of their anticoagulationtherapy.

Dr. Garrett is a clinical pharmacist practitioner at Cornerstone Health Carein High Point, NC.