Role of the pharmacist in delivering point-of-care therapy for inpatients on warfarin at a teaching hospital in South Africa

Abstract

The wide variation in biological effect, narrow therapeutic range and pharmacokinetic and pharmacodynamic characteristics of warfarin require monitoring of the international normalised ratio (INR). Point-of-care results that are readily accessible for interpretation, allows the pharmacist to make dose adjustments immediately and face to face. The objective of the study was to optimise control of patients’ anticoagulation medicine by measuring and interpreting the patient’s INR with the coagulometer. All patients on warfarin admitted, during a period of five months, to the internal medicine wards of Dr George Mukhari Academic hospital were included. Demographics, diagnoses, medicines interacting with warfarin, and laboratory results were recorded. INR’s were measured with the coagulometer from blood of a finger prick. Follow-up INR monitoring took place until patients were discharged. Descriptive statistics were used to describe the data. Sixty patients were enrolled. Warfarin was most frequently prescribed for deep vein thrombosis (25%), heart failure (25%) and valvular heart disease (11%). Recommendations included dosage adjustment (55%), discontinued warfarin (18%), initial warfarin dose (8%), request for more laboratory results (8%) and wrong dosing interval (5%). Thirty-four (85%) recommendations were accepted. Vitamin K and amiodarone influenced INR readings. Thirty-six patients (60%) were discharged with stable INR values, 25% due to recommendations made by the pharmacist. Eight (13%) were discharged with unstable INR’s with recommendations not followed or too early for warfarin to stabilise. Point-of-care INR monitoring by the pharmacist resulted in patients being discharged with an INR within therapeutic range and contributed positively towards warfarin management.

Keywords: Warfarin, point-of-care therapy (POCT), pharmacist, coagulometer.