Do coxibs reduce prescription of gastroprotective agents? Results of a record linkage study

BACKGROUND Coxibs are claimed to be cost-effective drugs and reduced prescription of gastroprotective agents is assumed to be one of their major benefits. Real life prescription of these drugs may be substantially different than that considered in pharmacoeconomic analyses or claimed by drug companies, yet. Our objective was to evaluate whether coxibs were associated with reduced prescription of gastro-protective agents (GPAs, specifically proton pump inhibitors, H2 blockers and misoprostol) compared to non selective NSAIDs. METHODS A record-linkage study was performed using 2001 outpatient prescription data from the province of Modena (about 632,000 inhabitants, in Northern Italy). Logistic regression was used to calculate the odds ratio of GPA prescription for coxib and non-selective NSAID adult users (> 14 years). Three categories of users were further investigated: "acute", "chronic and "incident or new". Main outcome measures were same-day co-prescription and 30 days prescription of GPAs in coxibs and non selective NSAIDs users. To limit selection bias, data were adjusted for age, sex, DDD of coxibs and non selective NSAIDs received during 2001, DDD of GPAs and (for non-incident users) DDD of NSAIDs received during the previous 4 years RESULTS Same day co-prescription rates were similar considering the overall population and "acute" users. Chronic coxibs users instead showed higher co-prescription rates than chronic NSAIDs users (OR = 1.2, p < 0.05). GPA prescription within thirty days was also higher among all subgroups of coxibs users (OR ranging from 1.6 to 2.0, p < 0.001). CONCLUSION Assumptions made in pharmacoeconomic analyses on coxibs (lower GPA prescription associated with coxibs use) may be overly optimistic. Claims made through cost-effectiveness data should be carefully interpreted, and mechanisms for attributing drug prices revised accordingly.