A probable drug interaction was observed in 2 patients taking warfarin who were initiated on remdesivir and dexamethasone for the treatment of COVID-19, according to a case series recently published in the Journal of Pharmacy Practice.
The patients, a 71-year-old male and a 62 year-old-male, both on long-term warfarin therapy, presented to the emergency department with symptoms of COVID-19. Per the report, each patient’s international normalized ratio (INR) was within their specific goal and both denied any diet, lifestyle, or medication changes prior to admission.
“During admission, both patients experienced a marked elevation in INR within 24 to 48 hours of the initiation of remdesivir with dexamethasone for COVID-19 pneumonia directed therapy,” the authors reported. After several days of modification to their warfarin doses, both patients were stable enough for discharge and were counseled to continue monitoring per the instructions of their outpatient pharmacist.
Although the exact mechanism of action resulting in the interaction between dexamethasone, remdesivir, and warfarin is unknown, the authors concluded that there is potential for interaction based on a calculated Drug Interaction Probability Scale score of 5. “This probable interaction is demonstrated by marked INR elevations within 24 to 48 hours of initiation of the combination in 2 cases with patients with historically stable INR history,” the authors stated.
Landayan RP, Saint-Felix S, Williams A. Probable interaction between warfarin and the combination of remdesivir with dexamethasone for coronavirus disease 2019 (COVID-19) treatment: A 2 case report. J. Pharm. Pract. [Published online April 5, 2021]. doi: 10.1177/08971900211008623