Do physicians change prescription practice in response to financial incentives?

We assessed the impact on physician prescription behaviors of an outpatient prescription incentive program providing financial rewards to primary care physicians for saving prescription costs in South Korea. A 10% sample of clinics (N=1,625) was randomly selected from all clinics in the National Health Insurance claims database for the years 2009-2012, and all claims with the primary diagnosis of peptic ulcer or gastro-esophageal reflux diseases were extracted from those clinics' data. A clinic-level random-effects model was used. After the program, clinics in general medicine showed a lower prescription rate (by 0.8 percentage points), lower number of medicines prescribed (by 0.02), lower prescription duration (by 0.15 days), and lower drug expenditure per claim (by 740 won). Small clinics on the <25th percentile of a regional sum of monthly drug expenditure had shorter prescription duration (by 0.76 days), while large clinics on the ≥75th percentile and clinics in group practice had a higher prescription rate (by 1.5 and 2.5 percentage points, respectively) and a higher number of medicines prescribed (by 0.03 for group practice only) after the program. The outpatient prescription incentive program worked as intended only in certain subgroup clinics for the target medicines.