A STUDY OF THE LONGITUDINAL UTILIZATION AND SWITCHING-PATTERNS OF NONSTEROIDAL ANTIINFLAMMATORY DRUGS USING A PHARMACY-BASED APPROACH

The extent of the heterogeneity of drug utilization among NSAID users has not been extensively studied. We studied the longitudinal prescrib ing and switching patterns of NSAID users in a 1-year follow-up study in four German pharmacies. The study population consisted of 526 perso ns with an average age of 57 years. We observed that the legend durati on of prescription increased with age; 14.3 days for patients aged 44 or younger to 25.1 days for persons 75 years or older, and was depende nt on disease chronicity; 16.0 days for acutely ill persons compared t o 23.9 days for chronic patients. The average legend duration also var ied between different types of NSAIDs, from 18.0 days for ibuprofen to 29.1 days for tiaprofen. Switching from one type of NSAID to another proved to be related to the legend duration of prescription and patien t characteristics such as compliance with NSAID therapy, duration of t he disease and the effectiveness (poor tolerability or insufficient ef fect) of the NSAID therapy reported by the patients 4 weeks after recr uitment. We conclude that NSAID users cannot be viewed as an homogeneo us group of patients with respect to exposure time to the drug. This h eterogeneity should be considered in the exposure definition, the 'tim e-window' design of observational studies dealing with risk comparison s in particular. (C) 1997 John Wiley & Sons, Ltd.