Pharmacokinetics and Pharmacodynamics of Single Doses of Rivaroxaban in Obesity Patients Before and After Bariatric Surgery

Background

The prevalence of obesity and morbid obesity is increasing worldwide and is becoming an increasing medical and socioeconomic burden. Bariatric surgery leads to the most sustained reduction of weight and associated co-morbidities. Obesity is a risk factor for the development of venous thromboembolism and the association between obesity and postoperative VTE is well established. The incidence of symptomatic DVT and PE ranges from 0%-5.4%, respectively 0%-6.4% and remains uncertain. Although the overall incidence seems to be low, VTE represents a significant cause of morbidity and mortality after surgery. Most postdischarge VTE events occur within the first 30 days after surgery and therefore extended chemoprophylaxis after hospital discharge is the standard of care and should be considered especially for patients classified to be at high risk for VTE.

Anticoagulants are recommended for the prevention of VTE, but there is no consensus regarding optimal method of prophylaxis. Routine perioperative use of drugs such as low-molecular weight heparins (LMWHs), intermittent pneumatic compression and early mobilization are currently the major accepted forms. However, there is currently no class I evidence to provide guidance regarding the type or dose of antithrombotic prophylaxis after bariatric surgery. For parenteral application there is for example limited evidence to guide dosing of thromboprophylaxis in morbid obesity and higher dosages are necessary, because impaired absorption after subcutaneous application.

The knowledge of the effect of extremely high body weight on pharmacokinetic and pharmacodynamics parameters after bariatric surgery especially for novel orally administered anticoagulants that target specific factors in the coagulation cascade is scarce. One promising therapeutic option is rivaroxaban (BAY 59-7939, Rivaroxaban), an orally administered direct factor Xa inhibitor that is approved for several indications in the field of prevention and treatment of thromboembolic disorders.

In several types of bariatric surgery procedures, such as sleeve gastrectomy, Roux-en-Y gastric bypass and biliopancreatic diversion different parts of gastrointestinal tract are bypassed or removed. This could affect the absorption of medications. Absorption of rivaroxaban is dependent on the site of drug release in the GI tract. In a study looking at administration of the crushed tablet via a tube, a 29% and 56% decrease in AUC and Cmax compared to an oral tablet was reported when rivaroxaban granulate is released in the proximal small intestine. The effect of altered anatomy due to RYGB on oral drug absorption and bioavailability is currently unknown. Previous studies focused on drugs like metformin, sertraline or tacrolimus, but they yielded conflicting results. In a case report by Mahlmann et al. the absorption of rivaroxaban was immediate and not significantly impaired by bariatric surgery of the upper GI tract. However, data from larger patient collectives are not available.