Surveillance of a recently switched non-prescription medicine (diclofenac) using a pharmacy-based approach

Purpose - Postmarketing surveillance of prescription medicines is a routine practice, yet similar evaluation of non-prescription medicines, including those recently switched from prescription status, is uncommon. This study presents the methodologic issues and limitations of the use of pharmacies in the 'post-reclassification' surveillance of oral diclofenac potassium 25 mg which had been recently switched from physician prescription to non-prescription sale. Methods - Consenting user-purchasers were recruited from 175 New Zealand pharmacies over 4 months. Purchasers were mailed a questionnaire for completion 7 days post-purchase. Those purchasers who met criteria for being potentially 'at risk' of adverse events were re-surveyed 30 days post-purchase. A descriptive analysis was carried out using t-test and chi-square as appropriate. These results were compared to those from other types of studies in this area. Results - The 1240 recruited purchasers returned 990 valid questionnaires (80% response). Of these 557 (56%) met 'at risk' criteria and received the second questionnaire with 480 valid returns (86.2% response). Conclusions - Useful data was gathered on the 'real-life' usage of a medicine recently reclassified from prescription to non-prescription sale. The use of community pharmacies as recruiting centres was found to be effective. Copyright (C) 2000 John Wiley and Sons, Ltd