Interaction between Gemcitabine and Warfarin Causing Gastrointestinal Bleeding in a Patient with Pancreatic Cancer

Gemcitabine (Gemzar) is the only chemotherapeutic agent approved by the U.S. Food and Drug Administration (FDA) for the treatment of advanced pancreatic cancer. Thromboembolism requiring anticoagulation is a common paraneoplastic complication in these patients. We report a case of patient with pancreatic cancer, complicated by gastrointestinal bleeding following therapy with concomitant gemcitabine-warfarin (Coumadin).The patient was a 65-year-old male with medical history notable for atrial fibrillation for which he was taking warfarin 57.5 mg/week (international normalized ratio [INR] 1.94). He received capecitabine-radiotherapy for locally advanced pancreatic cancer. Later, he developed multiple liver metastases. The patient was started on gemcitabine. At the end of first cycle, he experienced bright red blood per rectum. His platelet count was normal, but his INR was noted to be significantly elevated at 8.00. Esophagogastroduodenoscopy (EGD) revealed 2 antral ulcers and a duodenal ulcer. The patient was stabilized and recovered without further incident.Patients with pancreatic cancer who receive warfarin and gemcitabine should be monitored for any potential drug interactions. Weekly prothrombin time (PT)/INRs for anticoagulated patients receiving gemcitabine is suggested.