Patterns of Prescription Switching in a Uniform-Pricing System for Multi-Source Drugs: A Retrospective...

Area of Science:

• Health Services Research
• Pharmaceutical Economics
• Clinical Pharmacy

Background:

• Generic drugs constitute 40% of the Korean prescription market, yet pharmacy-level substitution is limited.
• Physician concerns regarding clinical equivalence of generics persist despite regulatory confirmation of bioequivalence.
• Multi-source prescription switching (MSPS) may reflect physician prescribing behavior, necessitating policies for effective competition.

Purpose of the Study:

• To quantify physician-initiated MSPS in adults with hypertension or diabetes in Korea.
• To identify factors associated with physician MSPS behavior.

Main Methods:

• Retrospective cohort study using Korean National Health Insurance claims data (Jan-June 2014).
• Followed patients for up to 24 months to identify MSPS episodes during drug therapy courses (defined by 12 ± 3 visits).
• Defined MSPS as a change in product code within the same pharmaceutically equivalent drug code between consecutive prescriptions.

Main Results:

• 17.06% of 1,325,334 identified drug therapy courses involved at least one MSPS.
• MSPS rates varied significantly by physician practice setting (e.g., public health centers 26% vs. tertiary hospitals 15%) and drug market size (glimepiride 29% vs. cilnidipine 1%).
• Patient age and gender were not associated with MSPS behavior.

Conclusions:

• Physicians frequently engage in MSPS in Korea, contrasting with limited pharmacy-level generic substitution.
• Substantial variation in MSPS across provider settings and drug markets, independent of patient characteristics, indicates physician discretion.
• Targeted pharmacy benefit policies are needed to promote substitutability and competition among multi-source drugs.