Improvement of time in therapeutic range with warfarin by pharmaceutical intervention

Background Anticoagulation therapy with warfarin is highly effective for prevention and treatment of thromboembolic disorders. Nevertheless, its management is challenging especially in developing countries, where the medical access is difficult and patient education is poor. Objective To determine the effect of pharmaceutical intervention (PI) on the time in therapeutic range (TTR) of a group of anticoagulated patients from our referral center. Method A group of consecutive outpatients previously treated by usual medical care underwent PI. The intervention consisted in the identification and avoidance of food and drug interactions, the confection of medication schedule charts and education to patients regarding side effects and drug monitoring. Mean TTR before and after PI was compared through the Wilcoxon test for repeated measures. Regression analyses were performed to assess the relationship between a TTR level under 65% and potential explanatory variables. Results Mean TTR before PI was 37.4 ± 23.5% and after PI it raised to 67.0 ± 24.9%. Mean change in TTR was +29.5% (95% CI 14.5-44.6; p < 0.001). Before PI only 4 patients had TTR values above 65%, in contrast to 18 patients after PI. Conclusion Our findings support the efficacy of PI to improve TTR values in patients treated with warfarin.