OBJECTIVES: Cost-effectiveness analyses (CEA) generally assume constant drug prices throughout the model time horizon. Yet research has shown that such prices are not constant over time, often with significant price decreases after loss of exclusivity (LOE). The aim of this study was to explore the impact of using drug-specific historical prices on the incremental cost-effectiveness ratio (ICER). The influence of drug life cycle price development is illustrated using four exemplary case-study analyses.

METHODS: Four drugs that went out of patent between 2008 and 2013 were selected from an initial dataset of 250 drugs. Monthly (list-)pricing and prescription data for these four drugs were extracted. For each drug a published CEA model was identified, replicated, and modified with historical list price data, in order to compare ICERs based on constant drug list prices with estimates obtained when including drug life cycle list pricing. Subsequently, the impact of multiple incident patient cohorts over the model time horizon was investigated in scenario analyses by utilising multi-cohort model extensions.

RESULTS: Inclusion of historical pricing data compared to inclusion of constant prices, reduced the ICER with 0.2% to 42.7%. The difference in magnitude of the impact between models was dependent on the length of the drug prescription period relative to model time horizon, drug cost proportion relative to overall incorporated treatment costs and timing of LOE. Applying multicohort analyses, resulted in further reduction of the ICERs with the most substantial impact occurring in case-examples with relatively short treatment duration.

CONCLUSIONS: Assuming constant drug prices may lead to inaccuracies when estimating ICERs to inform healthcare decisions. Future research should focus on predicting life cycle price development of drugs to be incorporated in CEA.