Prevalence of Warfarin Drug Interaction and Warfarin Education Practice in Outpatient Setups of University Teaching Hospital: A Retrospective Chart Review and an Observational Study

Author(s): Tamrat Assefa Tadesse*, Minyahil Alebachew and Alebachew Woldu

Introduction: Pharmacokinetic, pharmacodynamic and narrow therapeutic index properties of warfarin makes it particularly susceptible to interactions with a number of prescription and nonprescription drugs, including dietary supplements and herbal medicines. Patients requiring warfarin should then be educated with respect to the therapy safety and effectiveness issues as this improves patient‘s knowledge and quality of anticoagulation.

Objective: To assess the prevalence of warfarin drug interaction (WDI) and its dispensing practice at outpatient departments (OPD) of Tikur Anbessa Specialized Hospital (TASH).

Methods: A cross sectional study was carried out in 360 adult outpatients whom warfarin was prescribed for various indications at cardiac and hematology clinics (CHCs) by reviewing their chart retrospectively. To assess warfarin dispensing practice at outpatient pharmacies of the hospital, direct observation using checklist was conducted towards pharmacy professionals’ services provision to patients regarding warfarin therapy. Micromedex online database was used to analyze drug interaction.

Results: Out of 360 study participants nearly two third (64.7%) of them were female patients. A total of 76 (21.1%) WDIs were identified in this study. Moderate type of interaction accounted for 75.4% and the remaining was major type of interactions. Among the identified warfarin related education practice, the highest points were on educating patients on their daily dose, when to take warfarin and telling them the name of drug they receive as such education were given to 74.1%, 67% and 59.8% of patients respectively. From the total of 112 of the actual warfarin dispensed to the patients, only 45 (40.2%) were labeled with how to receive the drug.

Conclusion: Prevalence of warfarin drug interaction was minimal among outpatients of CHCs of TASH. Warfarin dispensing practice at outpatient pharmacies of the hospital was not optimal.

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