Key result
Among Estonian outpatients aged 50 years or older receiving warfarin, 57% had potential drug interactions in their treatment regimens, most frequently with NSAIDs (14%).
Observational (n=7,175)
A high proportion (57%) of older outpatients on warfarin are prescribed potentially interacting medications, most commonly NSAIDs, highlighting a significant risk for adverse bleeding events in ambulatory care.
Answers are grounded in this paper and cite their sources.
Urges caution with NSAID co-prescription in older warfarin users; leaves open generalizability and outcomes across settings.
UNLABELLED: In Estonia, warfarin is widely prescribed by general practitioners to prevent and treat thromboembolic diseases. To date, there has been no systematic analysis of the potential risk of warfarin interactions with other drugs in the outpatient population. OBJECTIVE: The aim of the study was to analyze the incidence of potential interactions in prescription schemes in Estonia in a cohort of outpatients receiving warfarin treatment. METHODS: The retrospective study population included 203,646 outpatients aged 50 years or older of whom 7,175 received warfarin therapy. Patients who had used at least one prescription drug for a minimum period of 7 days concomitantly with warfarin were analyzed. Potential drug interactions were analyzed using Epocrates online, Stockley's Drug Interactions and domestic drug interaction databases. RESULTS: The average number of drugs used concomitantly with warfarin was 4.8 (SD=1.9) (males: 4.7 SD=2.0, females: 4.9 SD=2.0). No potential interactions in treatment regimens were found in 38% of patients, one potential interaction was observed in 29% and two or more potential interactions were observed in 33% of patients. The mean number of all potential interactions was 1.2 per patient and about the same in men and women. Potential interactions were associated with the number of drugs. Warfarin-related interactions were detected in 57% of patients, and the number of interactions related to warfarin per patient varied from 1 to 5. Most frequent were use of warfarin with NSAIDs (14%), followed by simvastatin (9%) and amiodarone (7%). CONCLUSIONS: This study shows that 57% of outpatients in Estonia receiving warfarin have drugs potentially interacting with warfarin in their treatment schemes. Most interactions (14%) with warfarin are associated with the prescription of NSAIDs.
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Gavronski et al. (2012) conducted an observational in Outpatients receiving warfarin therapy (n=7,175). Concomitant prescription drugs was evaluated on Incidence of potential drug interactions with warfarin. Among Estonian outpatients aged 50 years or older receiving warfarin, 57% had potential drug interactions in their treatment regimens, most frequently with NSAIDs (14%).
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