Background COX-2 specific inhibitors (COX-2) are potentially prescribed to individuals at higher risk for adverse gastrointestinal (GI) outcomes, which produces “channelling” bias in nonrandomized observational studies. This bias may be minimised if the units of observation are the multiple drug exposure periods within high risk patients (ie individuals may be have both NSAID and COX-2 exposure periods).
Objectives To quantify the relative risk reduction of GI events associated with the use of COX-2 and traditional NSAIDs in a high risk cohort.
Methods All patients prescribed at least one COX-2 (celecoxib, rofecoxib) between 1/1–05/31/00 were identified from a ~3,000,000 member health maintenance organisation. Using physician recorded primary diagnoses, the following endpoints were examined: nonhospitalized GI discomfort (abdominal pain, nausea, dyspepsia, ulcer diagnosis without endoscopy) ± gastroprotective agent (GPA); and hospitalised or outpatient (with endoscopy) diagnosis of perforation, ulceration, or bleed (PUB). A multivariate Poisson regression model adjusting for the duration of drug exposure was used to compare the incidence of GI events associated with COX-2 or NSAID therapies (>200 years exposure). The analysis adjusted for traditional GI risk factors (age, gender, arthritis diagnosis, comorid disease, GI history, drug dosing, concomitant GPA therapy, history of cardiovascular disease, corticosteroid therapy).
Results The cohort consisted of 22,696 patients who received a total of 2,853 and 6,519 years of NSAID and COX-2 exposure, respectively. The patient demographics were: 33.8% male; 47% osteoarthritis; 12.4% rheumatoid arthritis; 28% GI history; 25% history of gastroprotective agent use; and 63.3 years of age. After adjusting for significant risk factors (α = 0.05), the relative risk reductions associated with COX-2 (bold) or NSAID therapy, using ibuprofen therapy as the standard, were as follows:
Conclusion Consistent with clinical trial results, improved GI tolerability and safety is associated with the utilisation of COX-2 therapy compared to NSAIDs.
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