Objective: The objective of this study was to examine the relationship between a pharmaceutical product's impact on health-related quality of life (HRQOL) and differential product price.

Methods: Design: An exhaustive search of the literature was conducted to acquire all HRQOL evaluations of pharmaceutical products that utilized a test-retest experimental approach. Data Collection: Effect sizes were calculated from the data extracted for 31 products. Average wholesale price for each product and similar products in the corresponding therapeutic class were collected, as well as the number of products in the class, availability of a generic and the percent of generics in the class, and whether the product was the lowest cost product in the class. Cost per day of therapy at the recommended starting dose and the ratio of the product cost to the lowest cost product in class were calculated. Analysis: Multivariate linear regression and analysis of variance models were constructed where either average wholesale price or cost per day of therapy was the dependent variable and effect size, therapeutic class, and other cost data were independent variables. Diagnostics were performed to verify model assumptions. Results: Using multivariate linear regression, the number of months on the market, ratio of drug price to lowest price drug in class, number of drugs in the class, and average effect size were significant, with a model R-square = 0.65. In the reduced model, the percent of generics in the therapeutic class was removed and the remaining independent variables were significant, with a model R-square = 0.61. Diagnostics revealed no violations of model assumptions. Conclusions: There is sufficient evidence to suggest that there is a direct positive relationship between a pharmaceutical product's ability to cause improvement in HRQOL and the price of the product. In addition, the number of products within a therapeutic class influenced drug price. This is interpreted as providing evidence for the validity of HRQOL measurement, and for the existence of product competition in the pharmaceutical industry. Further research should be conducted to evaluate the impact of prescription medications on HRQOL, and to identify and characterize the effects of drug and marketplace variables on drug prices.