Background OA is the most common and costly chronic musculoskeletal conditions. Celebrex® (celecoxib), which will become generic in the US in 2015, is a COX-2 selective inhibitor for pain relief for OA. Literature to date does not address rates of treatment switch from celecoxib to generic NSAIDs.
Objectives The study aimed to measure celecoxib adherence, persistence, and rates of switch to generic NSAIDs and understand comparative rates of treatment-emergent events for patients who switched from celecoxib to generic NSAIDs vs persistent patients; also compared were before- versus after-switch among switched patients.
Methods The retrospective claims database analysis used MarketScan® (2009–2013) to extract a cohort of adult OA patients (ICD-9-CM: 715.xx) who were new users of celecoxib prescription. Included patients had 12 months continuous enrollment before (pre-index period, without celecoxib) and ≥6 months after the index date with ≥2 celecoxib claims post-index. Adherence was measured by medication possession ratio (MPR). Persistence was defined as time to the first prescription gap of ≥30 days. Treatment switch required a fill for generic NSAIDs within 30 days of the end of celecoxib day supply. The likelihood of developing gastrointestinal (GI), cardiovascular (CV), renal and neuro-muscular (rheumatoid arthritis, ankylosing spondylitis, low back and other back/neck pain, fibromyalgia, arthritis/other arthropathies, diabetic/peripheral neuropathy) events while taking celecoxib was compared between switched and persistent celecoxib users in propensity score matched cohorts. Similar methods were used to compare outcome events before versus after switch among the switched patients. Cox proportional hazard models were employed to identify characteristics associated with time-to-switch.
Results Of 65,530 included patients (mean ± SD: age 61±11.9; 62.5% female), 6,783 (10.4%) were persistent on celecoxib after 13.6±7.7 months of follow-up (maximum 44.4 months). The majority (54,554, 83.3%) discontinued celecoxib without switching and 3,475 (5.3%) switched to generic NSAIDs (median time to switch or discontinuation 2.96 months). Persistent users were more adherent (MPR≥0.8) than switched (92.9% vs 78.5%, p<.001). Treatment-emergent events were higher for switched than persistent patients while taking celecoxib (Figure 1a). Among switched patients, post-switch incidence of treatment-emergent events were higher than pre-switch (Figure 1b). More likely to switch sooner were younger patients from Northeast region with more pre-index inpatient days, pre-index pain medications use, less adherence to celecoxib (MPR<0.8), no pre-switch bleeding, myocardial infarction or renal disorders, and no treatment-emergent GI, CV or neuro-muscular events.
Conclusions Within the cohort, relatively few patients switched from celecoxib to generic NSAIDs, although half discontinued in 3 months of celecoxib initiation. There was a higher incidence of GI, CV, renal and neuro-muscular events for switched than persistent patients. Among switched patients, higher incidence of post-switch vs pre-switch events suggested that these events were more likely to occur post-celecoxib when taking generic NSAIDs.
Disclosure of Interest X. Ji Grant/research support from: Pfizer Inc., Employee of: Pharmerit International, J. Cappelleri Shareholder of: Pfizer Inc., Employee of: Pfizer Inc., C. Solem Grant/research support from: Pfizer Inc., Employee of: Pharmerit International, S. Liu Grant/research support from: Pfizer Inc., Employee of: Pharmerit International, A. Shelbaya Shareholder of: Pfizer Inc., Employee of: Pfizer Inc., C. Walker Shareholder of: Pfizer Inc., Employee of: Pfizer Inc.