Drug switching patterns among patients taking non-steroidal anti-inflammatory drugs: a retrospective cohort study of a general practitioners database in the United Kingdom

Objective To examine the frequency and determinants of switching between different non-steroidal anti-inflammatory drugs (NSAIDs) and the relationship with co-prescription of gastro-protective drugs (GPDs). Design This was an analysis of 30 654 patients receiving a total of 209 140 NSAID prescriptions in the UK from 1 January 1997 to 31 December 1998 identified through the MediPlus database. Analyses examined switching, repeat, termination and GPD co-prescription rates in new and continuing takers according to age and sex. Results Each patient received an average of 6.8 prescriptions in the year of study. Of the prescriptions 72.2% were for one of three NSAIDs, ibuprofen, diclofenac, or naproxen, and 7.2% of prescriptions were for fixed combination products of an NSAID plus a gastroprotective drug. At least 16.0% of continuing takers, and 28.5% of new takers switched to another NSAID in the review period. On average, new patients switched more frequently than continuing patients (0.39 switches/patient/year versus 0.23 switches/patient/year, p<0.001). Switching between NSAIDs decreased with age and was less common in women (p<0.05). Switching was associated with a 24% and 33% increased probability of GPD prescription in new and continuing takers, respectively. Discussion The frequency of switching, and of GPD co-prescription at switching, suggest that dissatisfaction with NSAIDs is frequent, and that gastrointestinal intolerance is a common feature of this dissatisfaction. Copyright (C) 2001 John Wiley Sons, Ltd.