Correlation between rivaroxaban (Xarelto) plasma activity, patient clinical variables and outcomes in a South African centre : research

• Published in: South African medical journal Vol. 106; no. 10; pp. 1017 - 1020
• Main Authors: Ferrao, P.N., Jacobson, B.F., Chirwa, T.F., Saragas, N.P., Louw, S.
• Format: Journal Article
• Language: English
• Published: Health and Medical Publishing Group (HMPG) 01.10.2016
• ISSN: 0256-9574; 2078-5135
• DOI: 10.7196/SAMJ.2016.v106i10.10584

Background. Low-molecular-weight heparin and vitamin K antagonists such as warfarin are the gold standard for prohylaxis and treatment of venous thromboembolic disease (VTED). Direct oral anticoagulants (DOACs) result in predictable anticoagulation with significantly reducedinter- and intra-patient variability. DOAC absorption is rapid, with a short half-life and relatively few drug interactions. DOACs are effective and safe at fixed doses without activity monitoring. However, specific situations may require assessment of accurate drug activity. Rivaroxaban, a DOAC targeting activated coagulation factor X (FXa), is registered for the prevention and treatment of VTED in South Africa. Objectives. To establish a prophylactic rivaroxaban activity level range and determine any associations with clinical complications, viz. haemorrhage and/or thrombosis. Methods. Samples from 115 orthopaedic patients were tested 3 hours after a prophylactic oral dose of 10 mg rivaroxaban with STAGOrivaroxaban anti-FXa reagent on an automated coagulation analyser. Patient demographics and clinical outcomes were documented. Results. The mean rivaroxaban anti-FXa level was 105.7 ng/mL. Two patients developed adverse events on therapy. One patient had minor bleeding (menorrhagia) (drug activity level 288.7 ng/mL) and another a deep-vein thrombosis (drug activity level 34.7 ng/mL). Statistical analysis demonstrated an association between drug activity and advancing age (p=0.008), most apparent among those aged ≥65 years. Conclusions. Measuring rivaroxaban activity levels may reduce uncertainty if treatment failure and complications occur. Patients aged ≥65 years should be closely monitored. A local expected rivaroxaban activity level for patients on rivaroxaban prophylaxis has been established.