Using primary care prescribing databases for pharmacovigilance.

AIMS: In the UK, adverse drug reactions (ADRs) are responsible for over 6.5% of all hospital admissions, representing a significant morbidity and cost burden to the health service. We aimed to develop an ADR monitoring system capable of identifying the reasons for patient discontinuation of drug therapy within 6 months of the index prescription.
METHODS: Patients first prescribed amlodipine between 1 March 2004 and 28 February 2007 who discontinued their amlodipine medication within 6 months of the index prescription were identified from the practice team information (PTI) database. Once identified, reasons for amlodipine discontinuation were assessed by an electronic database search using relevant Readcodes and key words and by a direct approach to the primary care medical records.
RESULTS: The PTI database identified 995 patients [61.4% females, mean age 65.9 years (SD 12.4 years)] who discontinued amlodipine within 6 months of an index prescription. An electronic search of the database, using Readcodes, identified that 19.4% (193) of patients who discontinued their medication had an ADR recorded in the database. Six (20%) of 30 participating primary care practices, contributing to the PTI database, agreed to be approached directly and supply the reasons for discontinuation for the 51 patients identified as having discontinued amlodipine in their practices. Completed data were returned for all 51 patients, 98% of whom discontinued amlodipine due to an ADR or adverse drug event.
CONCLUSIONS: The results of this study confirm that primary care prescribing databases can be easily used to identify the frequency and nature of ADRs occurring in an ADR-enriched population identified through medication discontinuation.