Comparison of Price Index Methods and Drug Price Inflation Estimates for Medications for Opioid Use Disorder (MOUD)

OBJECTIVES: Drug price inflation has garnered significant attention in the United States due to concerns over medication affordability. Measuring drug price inflation is challenging due to the constant introduction of new drugs into the market and some branded drugs transitioning to generics, and existing indexes do not capture these transitions. This study aimed to evaluate how different price index methods affect estimates of drug price inflation and to develop a class-level index using Medications for Opioid Use Disorder (MOUD) as a case study.

METHODS: We conducted a cross-sectional analysis using outpatient Medicare Part D drug spending data for all generic and branded MOUD ever on the market from 2017 to 2021. National Drug Codes (NDCs) of MOUD was used to compile all Medicare Part D spending on MOUD based on the Substance Abuse and Mental Health Services Administration (SAMHSA) treatment guidelines. Product-level and class-level definitions of product and quantity was used to develop price indexes based on gross prices and actual prescription counts of the medications.

RESULTS: We identified a total of 18 distinct MOUD regimens in Medicare Part D claims from 2017 to 2021. Using 2017 as the base year and a class-level approach accounting for higher price of new drugs, chained-Laspeyres price index based on gross spending showed a 23% price increase for MOUD. At the product-level, brands of buprenorphine had the highest gross price increases from 2017 to 2021, with as high as 40% price increase, while brands of methadone had 11% to 28% gross price decrease.

CONCLUSIONS: This cross-sectional study found that a class-level approach of drug price inflation calculation may better estimate price increases as new drugs enter the market by considering high launch prices of drugs.