Introduction: Oral anticoagulation with warfarin is indicated for patients with prosthetic heart valves. The effects of religious fasting during Ramadan month (in the Islamic calendar) on anticoagulation aren't clear.
Objectives: To study the impact of Ramadan fasting on international normalized ratio (INR), quality of anticoagulation, dose of warfarin used and blood osmolarity.
Methods: 18 patients were followed-up prospectively for 3 months (pre- Ramadan, Ramadan and post-Ramadan months). Patients presented for weekly visits in which blood samples were obtained.
Results: No significant difference in INR and warfarin dose was found between Ramadan month, and months before and after it. The post-Ramadan INR was significantly larger than pre-Ramadan (p = 0.004). Blood osmolarity was significantly lower during Ramadan compared to pre- and post-Ramadan months. A significantly better quality of anticoagulation was noticed during Ramadan (p < 0.001). A significantly larger ratio of supratherapeutic INR values occurred in the post-Ramadan month (p < 0.05). A significantly larger ratio of infra-therapeutic INR values was noticed in the pre-Ramadan month (p < 0.05).
Conclusion: No significant difference in mean INR or warfarin dose was found and a better quality of anticoagulation was achieved during Ramadan. A tendency toward supra-therapeutic anticoagulation occurred after Ramadan, thus a closer follow up during this period may be reasonable.
Keywords: Antithrombotic therapy; Coumadin; International normalized ratio; Muslim; Prothrombin time.