Prescriber adoption of newly approved selective COX-2 inhibitors

Introduction: There is no consistent definition of prescribers who adopt new drug treatments early. This study examines if COX-2 inhibitors (coxibs) were prescribed by subsets of practitioners and describes GP adoption patterns of coxibs and existing NSAIDs over time.

Methods: A population-based drug utilisation study using a Dutch medication claims database. Prescribers of patients (18+yrs) prescribed an NSAID January 1999-December 2003 were identified. Four NSAID categories were chosen reflecting selectivity (coxibs, preferential COX-2 inhibitors and non-selective (ns) NSAIDs (sub-categorised as first or second line treatment)). The characteristics of prescribers issuing>10 prescriptions examined were: Type (GP, Specialist, Other); GP NSAID prescribing preference ratio (nsNSAIDs/coxib first prescription); coxib (ratio<3); prescriber proportion responsible for 100%, 80% and 50% of initiations. Odds Ratios (95%CI) were calculated (first-line nsNSAIDs as reference). Plots of prescribing proportions by quarter year were examined.

Results: NSAID cohorts comprised: first-line ns (N=38783); second-line ns (N=1459); COX-2 preferential (N=3107); coxib (N=4202) patients. For all four cohorts, GPs were the most common prescriber type (>67%); the most frequent prescribing preference was for first-line nsNSAIDs; 50% percentile prescribing proportions were low (<9%). GPs were equally as likely to prescribe coxibs as first-line nsNSAIDs [OR 1.0 (0.9, 1.1)]. Plots of 100% prescriber proportion for first-line nsNSAIDs and coxibs showed convergence; 50th percentile prescriber proportions plots were constant.

Conclusions: Small subsets of prescribers accounted for the majority of initiations regardless of NSAID type. Further studies are needed on such prescribers to inform healthcare policies and encourage participation in post-marketing safety studies.