Pharmacovigilance of over-the-counter products based in community pharmacy: methodological issues from pilot work conducted in Hampshire and Grampian, UK

Abstract

Purpose: The incidence of serious adverse events from non-prescription medicines remains to be established. The aim of this initial pilot work, using an observational cohort design, was to determine the feasibility of conducting a pharmacovigilance study of a non-prescription medicine, based in community pharmacies.

Method: Community pharmacists from Grampian, Scotland, and Hampshire, England, recruited user-purchasers of ibuprofen. Exposure data were collected from a series of self-completed questionnaires. Outcome data were any new symptoms, use of concomitant medication and subsequent health-care utilization.

Results: A total of 1021 eligible customers were recruited, 6.4% (466/7320) and 48.2% (555/1152) by the Hampshire and Grampian networks respectively. The cohorts differed with regard to age, smoking and socio-economic status, reason for purchase and recommendation, and duration of use. The two cohorts reported different use of concomitant medication (46.0 and 65.5%), asthma (7.2 and 10.5%), stomach/peptic ulcer (3.5 and 2.1%), a higher prevalence of gastrointestinal symptoms post-compared to pre-purchase (12.9 vs. 7.2%, p = 0.0006 and 8.8 vs. 5.8%, p = 0.034), ingestion of doses in excess of the licensed non-prescription dose by 5.1 and 3.9%, and discontinuation of treatment because the medicine upset them by 4.5 and 3.1%, respectively. Most participants did not seek medical advice for their symptoms.

Conclusion: Greater vigilance is required for adverse events that may be attributable to non-prescription product use. Development of pharmacovigilance models using community pharmacies is one means of systematically collecting information regarding drug safety. Further work is needed to identify a method which maximizes patient recruitment whilst maintaining acceptable follow-up rates.