The impact of a national prescription drug formulary on prices, market share, and spending: lessons for Medicare?

Several recent bills in Congress to add a Medicare prescription drug benefit would allow the use of formularies to control costs. However, there is little empirical evidence of the impact of formularies among elderly and disabled populations. We assess the effect of a closed formulary implemented by the Veterans Health Administration (VHA) in 1997 on drug prices, market share, and drug spending. We find that the VHA National Formulary was effective at shifting prescribing behavior toward the selected drugs, achieving sizable price reductions from manufacturers, and greatly decreasing drug spending.