Analgesic use before and after oral anticoagulant initiation - a population-based study in Finland

Purpose: Due to potential drug-drug interactions and subsequent bleeding risk, analgesic use should be reviewed when an oral anticoagulant is initiated. The aim of this study was to compare use of non-steroidal anti-inflammatory drugs (NSAIDs) and other analgesics before and after oral anticoagulant initiation.
Methods: All individuals who initiated warfarin, dabigatran, or rivaroxaban between January 2012 and September 2013 were identified from the Finnish Prescription Register. Prevalence of analgesic use during 3 months after oral anticoagulant initiation was compared to analgesic use during 4 months before initiation. Analgesics included were NSAIDs, paracetamol, paracetamol in doses ≥2 g/day, tramadol, and other opioids. Conditional logistic regression was used to calculate odds ratios (OR) with 95 % confidence intervals (CI).
Results: In total, 54,025 initiated warfarin, 16,894 rivaroxaban, and 1569 dabigatran. The odds of NSAID use decreased among warfarin initiators (odds ratio (OR) 0.10; 95 % confidence interval (CI) 0.09-0.10); 2.6 % used NSAID after initiation. In contrast, the odds of NSAID use increased among rivaroxaban (OR 3.56; 95 % CI 3.37-3.75) and dabigatran initiators (OR 1.44; 95 % CI 1.16-1.78). The proportions using NSAIDs after the initiation were 69 and 32 %, respectively. However, NSAID use decreased among dabigatran initiators with confirmed atrial fibrillation (OR 0.46; 95 % CI 0.23-0.92) and among rivaroxaban initiators with a daily dose of ≥15 mg (OR 0.28; 95 % CI 0.19-0.40).
Conclusions: The use of NSAIDs decreases extensively among warfarin initiators which is encouraging. However, the use of NSAIDs increases among rivaroxaban and dabigatran initiators. This is a concern as the bleeding risk may increase due to potential pharmacodynamic interactions.