Therapy switching and associated costs in elderly patients receiving COX-2 selective inhibitors or non-selective non-steroidal anti-inflammatory drugs in Quebec, Canada

Abstract

Lack of efficacy or tolerability of some non-steroidal anti-inflammatory drugs (NSAIDs) may lead to switching between non-selective NSAIDs (nsNSAIDs) and cyclooxygenase-2 (COX-2) selective inhibitors (coxibs), potentially increasing treatment costs due to additional physician visits and wastage of medication. This study assessed drug switching and associated costs among elderly chronic NSAID users. Data for patients who filled their first prescription for a coxib or nsNSAID in 2001 were obtained from the Quebec Health Insurance Agency. Follow-up was terminated at the earliest of: 1 yr, the first day without NSAID exposure following the index filling date, or death. Patients could switch NSAIDs several times during follow-up. Person-days of exposure were categorized by the NSAID most recently dispensed: rofecoxib, celecoxib, Arthrotec(R) or non-Arthrotec (nA) nsNSAID. Cox regression models compared time to switch between groups, adjusting for patient baseline characteristics. Upon a switch, pills remaining from the previous prescription were considered wasted. The costs of wasted pills and switch-associated physician visits were estimated. Throughout follow-up, patients filled 38 267 prescriptions for rofecoxib, 31 282 for celecoxib, 1108 for Arthrotec and 4388 for nA-nsNSAIDs. Adjusted hazard ratios (95% confidence interval) for switching versus nA-nsNSAIDs were: rofecoxib, 0.39 (0.35-0.44); celecoxib, 0.43 (0.38-0.48). Compared with nA-nsNSAID prescriptions, adjusted switching-related healthcare costs were 53 and 47% lower on average for rofecoxib and celecoxib prescriptions, respectively. These costs were 34% higher for Arthrotec prescriptions than for nA-nsNSAIDs. Compared with recipients of nsNSAIDs, coxib recipients were less likely to switch medications and had approximately half the adjusted costs for switching-related wasted resources per prescription.