Pharmacokinetics and pharmacodynamics of drug‒drug interactions in hospitalized older adults treated with direct oral anticoagulants

Purpose: Polypharmacy is a frequent situation in older adults that increases the risk of DDIs, both PK and PD. DOACs are frequently prescribed in older adults, mainly because of the high prevalence of atrial fibrillation (AF). DOACs are subject to cytochrome P450 3A4 (CYP3A4)-and/or P-glycoprotein (P-gp)-mediated PK DDIs and PD DDIs when co-administered with drugs that interfere with platelet function. The aim of our study was to assess the prevalence of DDIs involving DOACs in older adults and the associated risk factors at admission and discharge. Methods: This was a cross-sectional study conducted in an acute geriatric unit between January 1, 2018 and December 31, 2022, including patients over 75 years of age treated with DOACs at admission and/or discharge, for whom a comprehensive collection of co-medications was performed. Results: From 909 hospitalizations collected, the prevalence of PK DDIs involving DOACs at admission was approximately 17-21%, and the prevalence of PD DDIs was approximately 20-21%. Factors associated with DDIs were bleeding history [adjusted odds ratio (ORa) 1.74, 95% confidence interval (CI) 1.13–2.68], number of drugs > 6 (ORa 2.54, 95% CI 1.88-3.46) and reduced dose of DOACs (ORa 0.39, 95% CI 0.28–0.54) at admission and age > 87 years (ORa 0.74, 95% CI 0.55–0.99), number of drugs > 6 (ORa 2.01, 95% CI 1.48–2.72) and reduced dose of DOACs (ORa 0.41, 95% CI 0.30–0.57) at discharge. Conclusion: This study provides an indication of the prevalence of DDIs as well as the profile of DDIs and patients treated with DOACs.