Gastrointestinal bleeding after the introduction of COX 2 inhibitors: ecological study

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Abstract
We did a population based cross sectional time series analysis using administrative healthcare databases covering more than 1.3 million residents of Ontario, Canada, aged at least 66 years.4 This population has universal access to hospital care, doctors' services, and prescription drugs on a formulary. The study's timeframe was divided into 15 intervals of six months from 1 September 1994 to 28 February 2002. Rofecoxib and celecoxib were introduced on the provincial drug formulary in April 2000 and meloxicam was introduced in March 2001. The prevalence of use of NSAIDs in each interval was determined by dividing the unique number of individuals dispensed any NSAID (either non-selective NSAIDs or COX 2 inhibitors) by the total number of individuals alive at the beginning of the interval. Similarly, we examined hospitalisation rates for upper gastrointestinal haemorrhage. As secondary endpoints, we examined hospitalisations for myocardial infarction and heart failure. We standardised all rates for age and sex. As supplementary analyses, we also examined changes in the use of gastroprotective agents, oral corticosteroids, prescription aspirin, and warfarin, since these factors may be strongly related to upper gastrointestinal haemorrhage. We used time series analysis involving autoregressive integrated moving average models to evaluate changes over time with the package SAS 8.2 (SAS, Cary, NC).5