Background: The major problem in prescribing the therapeutic dose of warfarin, the most clinically used anticoagulant, is achieving its optimal International Normalized Ratio (INR). This study was designed to determine the mean dose of warfarin among the patients admitted to Kashan Heart Clinic in 2008.

Materials and Methods: In this cross-sectional study, the medical documents of all patients receiving warfarin in any medical indications were studied for demographic specification, INR results, smoking, other used drugs and the underlying diseases. The warfarin dose attained (INR equal to 2.4-2.6 for 3 consecutive test results) was regarded as the optimal dose. All unqualified cases in terms of INR criteria were excluded. Statistical analysis was done using ANOVA, Pearson, Spearman and T-tests.

Results: Seventy one out of 86 patients were included in the study. The mean daily dose of warfarin was 3.97±1.38 mg. Fourty six, 13, 11 and one patient(s) received warfarin for atrial fibrillation, prosthetic valve, congestive heart failure and embolic cerebrovascular accident, respectively. While warfarin dose had an inverse relation to age (P=0.01), it had no significant relation with sex (P=0.7), underlying diseases (P>0.07), smoking (P=0.2), other used drugs (P=0.07) and the patient weight (P=0.1). The results showed that warfarin dose was higher among the patients with prosthetic valve (P=0.008).

Conclusion: The obtained effective daily and weekly dose of warfarin i.e. 3.97±1.38 and 27.83±9.77 mg, respectively could be used as a therapeutic clue for prescribing the appropriate dose and optimum INR.