Physiologically-based pharmacokinetic modeling to predict drug-drug interactions of dabigatran etexilate and rivaroxaban in the Chinese older adults

INTRODUCTION: Drug-drug interaction (DDI) is one of the major concerns for the clinical use of NOACs in the older adults considering that coexistence of multiple diseases and comorbidity were common. Current guidelines on the DDI management were established based on clinical studies conducted in healthy adults and mainly focus on the Caucasians, whereas systemic and ethnic differences may lead to distinct management in the Chinese older adults. OBJECTIVES: To investigate the impact of aging on the DDI magnitude between P-gp and/or CYP3A4 inhibitors with dabigatran etexilate and rivaroxaban in older adults, providing additional information for the use in clinical practice. RESULTS: Compared with the simulated adult, the AUC of the simulated older adults increased by 42–88% (DABE) and 21–60% (rivaroxaban), respectively, during NOACs monotherapy. Simulation on DDIs predicted that verapamil and clarithromycin further increase the exposure of dabigatran by 29–72% and 40–47%, whereas clarithromycin, fluconazole, and ketoconazole increase the exposure of rivaroxaban by 21–30%, 16–24%, and 194–247% in the older adults. Overall, our simulation result demonstrated that aging and DDIs both increased the exposure of NOACs. However, aging does not have a drastic impact on the extent of DDIs. The DDI ratios of young and old older adults were similar to the adults and were also similar between Caucasians and Chinese. DISCUSSION: We further simulated the interactions under steady-state based on the EHRA guideline (2021). Our simulation results revealed that recommended reduced dosing regimen of dabigatran etexilate during comedication with verapamil and clarithromycin (110 and 75 mg BID for Chinese young and old older adults) will result in exposure (trough concentration) that was either slightly higher or similar to the trough concentration of patients with any bleeding events. Routine monitoring of bleeding risk is encouraged. Further studies on the use of rivaroxaban in Chinese older adults are warranted. CONCLUSION: Aging and DDI increases exposure of drug in Chinese older adults. However, aging does not have a drastic impact on the extent of DDIs. Clinical management of DDIs in Chinese older adults in the absence of complex polypharmacy can a priori be similar to the EHRA guideline but routine monitoring of bleeding risk is encouraged when dabigatran etexilate given with verapamil and clarithromycin.