Warfarin maintenance dose in Iranian patients. A cross sectional study in 5 cities of Iran

OBJECTIVE: To determine the warfarin maintenance dose in Iranian patients.

METHODS: This multicenter study was conducted between January 2007 and January 2008 in 5 different large cities of Iran. Patients older than 12 years receiving warfarin were included. During the first days of warfarin use, international normalized ration (INR) was measured daily and after that every 1-2 weeks, with a duration of at least one month. The warfarin dose was considered to be stabilized if the INR remained unchanged on 3 consecutive measurements at a level between 2-3. Then mean dose of the last 3 warfarin doses was calculated.

RESULTS: One hundred and fifty patients receiving warfarin took part in this study. No significant differences were noted in the mean warfarin dosage among the 5 cities, and between men and women (p=0.228). The warfarin daily dose and INR did not shown any statistical difference between men and women. The warfarin dose statistically decreased in patients older than 60 years old (p=0.004 versus 45-60 years, and p=0.002 versus 30-45 years). This study showed that the required mean warfarin dose in Iranian patients was approximately 4 mg to achieve an INR between 2-3.

CONCLUSION: Considering geographic and ethnic differences of Iranian patients, attention to the dose determination of warfarin is of importance.