A study of the longitudinal utilization and switching-patterns of non-steroidal anti-inflammatory 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 prescribing and switching patterns of NSAID users in a 1-year follow-up study in four German pharmacies. The study population consisted of 526 persons with an average age of 57 years. We observed that the legend duration 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 dependent on disease chronicity; 16.0 days for acutely ill persons compared to 23.9 days for chronic patients. The average legend duration also varied 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 patient characteristics such as compliance with NSAID therapy, duration of the disease and the effectiveness (poor tolerability or insufficient effect) of the NSAID therapy reported by the patients 4 weeks after recruitment. We conclude that NSAID users cannot be viewed as an homogeneous group of patients with respect to exposure time to the drug. This heterogeneity should be considered in the exposure definition, the 'time-window' design of observational studies dealing with risk comparisons in particular.
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Medical Department, Ciba-Geigy, 4002 Basel, Switzerland.
van Staa
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Abenhaim
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Ebner
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