RESUMO
BACKGROUND: Warfarin's therapeutic effect is affected by many factors, including diet modifications. The impact of Ramadan fasting on warfarin is controversial. The aim of this systematic review and meta-analysis was to investigate the effect of Ramadan fasting on patients taking warfarin. METHODS: A literature search was done in PubMed, WOS, Scopus, and Embase from inception to May 24, 2021. All relevant studies measuring the international normalized ratio (INR), time in therapeutic range (TTR), or the number of patients within therapeutic range before, during, and after Ramadan were assessed by full-text screening for achieving all of the inclusion criteria. We used the Newcastle-Ottawa Scale for quality assessment and RevMan 5.4 software for meta-analysis. RESULTS: A total of five studies with 446 patients were included in the meta-analysis. The patients served as their own control. Our pooled analyses showed no significant difference during Ramadan compared to pre-Ramadan (MD: 0.08; 95% CI: - 0.00, 0.15; P = 0.06) and post-Ramadan (MD: - 0.00; 95% CI: - 0.14, 0.14; P = 1.00, respectively). There was only a significant increase in the risk ratio of supratherapeutic INR when comparing post-Ramadan vs. pre-Ramadan (RR: 1.69; 95% CI: 1.22, 2.33; P = 0.001). However, there was no significant risk for supratherapeutic INR during Ramadan compared to pre-Ramadan or post-Ramadan; the number of patients within the therapeutic range of INR during Ramadan compared to pre-Ramadan; and TTR during Ramadan, pre-Ramadan, and post-Ramadan. CONCLUSION: Ramadan fasting did not affect INR level, TTR, or the number of patients within the therapeutic range before, during, and after Ramadan. However, there was a possibility of achieving a supratherapeutic INR post-Ramadan compared to pre-Ramadan. Therefore, INR monitoring and warfarin dose adjustments accordingly are recommended after Ramadan.