Background: Prescribing DOACs present with challenges in the elderly and patients with renal and hepatic impairment. To mitigate safety risks, pharmacists have a role in detection, prevention and resolution of DOAC-associated drug related problems (DRPs).
Aims: To identify the types of DOAC-associated DRPs in patients on DOAC therapy and factors which predispose patients to DOAC-associated DRPs.
Methods: A case-control study conducted in SGH from 1st January 2017 to 31st May 2019 on patients prescribed with a DOAC (rivaroxaban, dabigatran and apixaban). Data were electronically extracted for patient demographics, clinical characteristics and details of DOAC-related DRPs identified by pharmacists. Case-control matching at ratio 1:2 based on gender, race and DOAC was performed. Cases were patients with DRPs while controls were patients without. Descriptive analysis was used to summarise patient characteristics and types of DOAC-associated DRPs. In the matched population, conditional logistic regression was used to calculate unadjusted (UOR) and adjusted odds (AOR) ratio to detect association with DOAC-associated DRPs for age, renal function, ≥2 co-morbidities and DOAC indication (atrial fibrillation (AF) vs venous thromboembolism (VTE)).
Results: A total of 8,432 patients prescribed DOACs were analysed which consisted of 827 (9.8%) and 7,602 (90.2%) patients with DRPs and no DRPs respectively. The top DOAC-associated DRP was inappropriate drug regimen (n=487, 60.1%). After matching, 2,403 patients were analysed, consisting of 801 cases and 1,602 controls. Factors associated with DOAC-associated DRPs was statistically significant for renal function at creatinine clearance (CrCl) 30-50ml/min/1.73m2 (AOR 1.42, 95% CI 1.14–1.76, p=0.002), 15-30ml/min/1.73m2 (OR 1.94, 95% CI 1.42–2.66, p < 0.001), and ≤15ml/min/1.73m2 (OR 2.35, 95% CI 1.13–4.88, p=0.022) respectively compared with CrCl≥50mg/min/1.73m2 and DOAC indication for AF (AOR 1.84, 95% CI 1.47–2.30, p< 0.001) compared with VTE.
Conclusion(s): Inappropriate drug regimen was the most common DOAC-associated DRP. Impaired renal function and patients with AF increased the likelihood of DOAC-associated DRPs.