[Gastrointestinal hemorrhage due to a probable warfarin/oseltamivir drug interaction: A case report]

Bleeding while on vitamin K antagonist therapy is one of the main causes of iatrogenic hospitalization. There are few reports of a drug-drug interactions resulting in a serious bleeding complications between warfarin and oseltamivir.

We report the case of a 64-year-old woman hospitalized with anemia. She was on warfarin for mechanical heart valve prostheses (usual international normalized ratio, INR: 2.5-3.5) and had moderate renal insufficiency. Treatment with oseltamivir for influenza was introduced, leading to a rapid increase in the INR value within less than a week and a recurrence of digestive bleeding. Symptomatic management (antagonization with vitamin K and prothrombin complex concentrate) led to correction of the overdose.

When oseltamivir is introduced in a patient receiving warfarin, we suggest close monitoring of the INR, especially in the case of renal insufficiency, from initiation to the elimination of the oseltamivir (3 days after discontinuation).