Comparison of seasonal pattern in patients with warfarin overdose

Document Type : original articles


1 Cardiovascular Research Center, Tabriz University of Medical Sciences, Tabriz, Iran

2 Liver and Gastrointestinal Diseases Research Center, Imam Reza Hospital, Tabriz University of Medical Sciences, Tabriz, Iran


Objectives: The most common anticoagulant drug in the world is warfarin. Overdoses of warfarin may follow seasonal patterns, but the information is scarce. This study investigated possible seasonal variations in warfarin overdose among various age groups living in cold climates.
Methods: This retrospective study was carried out on 235 patients between 2014 and 2019 at Shahid Madani Hospital, Tabriz, Iran. The analysis was performed on the patients who had overdosed on warfarin and had INR (International Normalized Ratio) levels higher than four. After reviewing our database, we found seasonal patterns in admissions for overdoses caused by warfarin. The seasonality of access of patients older and younger than 65 years of age was compared between the two groups. The independent t-test was used to compare the quantitative data, and the Chi-square test was used to compare categorical variables using SPSS V. 20.0 software.
Results: Seasonal patterns were observed in warfarin overdoses. Warfarin overdoses were more common among the patients under 65 years old during winter (P-value = 0.03), whereas almost identical findings were found among the patients 65 and older, although numerically more cases were seen during the summer season (P-value = 0.8). Conclusions: The results of the current study showed that warfarin overdoses in the patients younger than 65 years showed a seasonal pattern peaking in the winter months. However, these findings did not have any relation with older patients. To confirm the results of the present study, larger prospective multicenter studies in a variety of climate settings are needed.