A Medicare database review found that physician preferences increasingly outweighed patient characteristics as determinants of first-time prescriptions for COX-2 inhibitors.
OBJECTIVE
Although innovative drugs may be underprescribed by some physicians, it is possible that rapid adoption after market introduction may lead to prescribing such drugs to patients without a clear indication. We sought to quantify the relative contributions of patient vs. physician factors to the decision to prescribe selective cyclooxygenase-2 (COX-2) inhibitors during the first 2 years of their availability.


METHODS
A cohort of 37,957 Medicare beneficiaries who were enrolled in the Pharmaceutical Assistance Contract for the Elderly in Pennsylvania was identified. All patients had started using nonselective nonsteroidal anti-inflammatory drugs (NSAIDs) or selective COX-2 inhibitors between January 1, 1999, and December 31, 2000, and had no prior NSAID use. All had full prescription drug coverage, including NSAIDs and selective COX-2 inhibitors. Subsequent prescriptions were not considered. We quantified the amount of variation in first-time COX-2 prescribing that could be explained by predictors of gastrointestinal (GI) toxicity, other patient characteristics, or physician preferences. Explained variation was calculated as the R(2) (standardized to range from 0 to 1) from unconditional logistic regression and random intercept mixed effects logistic regression, fitted separately in each of eight consecutive 3-month periods.


RESULTS
COX-2 inhibitors were adopted as the preferred NSAID by 55% of physicians within 180 days after they were marketed. In new NSAID users, COX-2 prescribing was twice as dependent on physician prescribing preferences (R(2)=60%) as on the combined predictors of GI toxicity (R(2)=3%) and other patient factors (R(2)=30%). The ratio of COX-2 prescribing explained by physician preferences over the contribution of patient factors increased from 2 to more than 10 over a 24-month period.


CONCLUSIONS
First-time COX-2 inhibitor prescribing was somewhat dependent on patient factors in the first quarter of marketing, but the proportional influence of physician preferences increased substantially over the following 2 years, raising the question of why physician factors and not patient risk factors influence COX-2 inhibitor prescribing.
Schneeweiss
Sebastian
S
Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 1620 Tremont Street, Suite 3030, Boston, MA 02120, USA. schneeweiss@post.harvard.edu
Glynn
Robert J
RJ
Avorn
Jerry
J
Solomon
Daniel H
DH
D000368:Aged; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000009:adverse effects; D015331:Cohort Studies; D016861:Cyclooxygenase Inhibitors / Q000627:therapeutic use; D017723:Drug Utilization Review / Q000379:methods*; D005260:Female; D006302:Health Services Research; D006801:Humans; D008297:Male; D006278:Medicare / Q000706:statistics & numerical data; D018579:Patient Selection; D010414:Pennsylvania; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data*; D012307:Risk Factors
D000894:Anti-Inflammatory Agents, Non-Steroidal; D016861:Cyclooxygenase Inhibitors