Analysis of potential interactions between warfarin and prescriptions in Estonian outpatients aged 50 years or more

Abstract

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.ObjectiveThe 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.MethodsThe 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. ResultsThe 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%). ConclusionsThis 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.

Co‐Prescribing of Potentially Interacting Drugs during Warfarin Therapy – A Population‐Based Register Study

“…Our findings on a high prevalence of co-prescribing of interacting drugs among community-dwelling persons receiving warfarin therapy accord with previous studies [15][16][17][18]. Besides the high prevalence, we illustrated that more than every second person initiating warfarin therapy were coprescribed interacting drugs early after initiation.…”

Frailty and Co-Prescribing of Potentially Interacting Drugs in New Users of Warfarin

“…NSAIDs have been among the most common interacting drugs in inpatients and outpatients taking warfarin [3,4,9,27]. This trend seems to have changed and similar results to ours have been recently published in large register-based studies [11,28,29].…”

“…More importantly, the excess risk caused by drug interactions is predictable and often avoidable by choosing alternative medications. Despite this, previous studies show that up to 60-80% of warfarin users, the majority of whom are older people, are exposed to potential drug interactions [9][10][11][12]. However, to our knowledge, there is no existing research on the frequency of warfarin drug interactions in frail patients compared to non-frail patients.…”

Synthesis of conductive polymeric ionic liquid/Ni nanocomposite and its application to construct a nanostructure based electrochemical sensor for determination of warfarin in the presence of tramadol

“…These diseases mainly affect older patients with atrial fibrillation, and this group of patients ultimately requires effective and well tolerated long-term therapy [2]. Presently, the most commonly used drug for the prevention of thromboembolic diseases is warfarin [3,4].Warfarin sodium, an inhibitor of vitamin K dependent clotting factor, has been a generally used anticoagulant drug since 1954 for preventing the blood from clotting owing to various cardiovascular signs or as a result of medical interference [5].…”