Anticoagulation in sub‐Saharan Africa: Are direct oral anticoagulants the answer? A review of lessons learnt from warfarin

Abstract

Warfarin has existed for >7 decades and has been the anticoagulant of choice for many thromboembolic disorders. The recent introduction of direct-acting oral anticoagulants (DOACs) has, however, caused a shift in preference by healthcare professionals all over the world. DOACs have been found to be at least as effective as warfarin in prevention of stroke in patients with atrial fibrillation and in treatment of venous thromboembolism. In sub-Saharan Africa, however, the widespread use of DOACs has been hampered mainly by their higher acquisition costs. As the drugs come off patent, their use in sub-Saharan Africa is likely to increase. However, very few trials have been conducted in African settings, and safety concerns will need to be addressed with further study before widespread adoption into clinical practice.

Anticoagulation control, outcomes, and associated factors in long-term-care patients receiving warfarin in Africa: a systematic review

“…Higher TTR is the best indicator of good anticoagulation management service [ 63 ]. The lower TTR reported in Africa questioned the quality of anticoagulation service [ 2 , 34 ]. Despite the presence of several risk factors, this might be partly explained by the limited and ineffective implementation of evidence-based AMS recommended by international guidelines.…”

Ethnic Diversity and Warfarin Pharmacogenomics

“…Implementing a pharmacogenomic-dosing algorithm in the European cohort increased the mean TTR to 67% ( Pirmohamed et al, 2013 ), which makes the anticoagulation quality gap with sub-Saharan Africa even wider as there is no validated pharmacogenomic dosing algorithm in this region at the moment ( Mouton et al, 2021 ). Moreover, Europe which is wealthier than sub-Saharan Africa is able to afford the more costly new direct oral anticoagulants (DOACs), whereas sub-Saharan Africa’s choices are mainly limited to warfarin due to its low cost ( Semakula et al, 2021 ). Because it is important that the quality of warfarin anticoagulation is optimal for all populations [warfarin is equal to DOACs in terms of safety and efficacy if it is given to patients who are able to maintain a time in therapeutic INR range ≥66% ( Ruff et al, 2014 )], we are currently developing a pharmacogenomic dosing algorithm for the two sub-Saharan countries and validating a point-of-care test that includes African-specific genetic variants in an ongoing collaborative project (War-PATH, Warfarin anticoagulation in PATients in sub-SaHaran Africa; http://warpath.info/ ).…”

Pharmacogenomics and health disparities, are we helping?

“…While DOACs have become the standard of care for patients with deep vein thrombosis compared to Vitamin K antagonists, low-income and black patients consistently receive less prescriptions of DOACs even when they are insured ( Nathan et al, 2019 ). Similarly, utilization of DOACs remain limited in African countries due to its unaffordability because of patent laws, in addition to lack of clinical trials to address its safety in African populations ( Semakula et al, 2021 ; Dandara et al, 2022 ). With a growing body of studies of DOACs PGx, efforts to enroll minorities, which most probably would also fall on a lower level of SES, is of paramount importance.…”