The DPI, or DestinationRx Price Index, is the price that a person who does not have prescription drug insurance should expect to pay for a given dosage and quantity of a drug. We think of DPI as the “blue book?reference for drug pricing. DPI is a proprietary calculation of DestinationRx, updated every other week, that factors in the negotiated prescription drug prices of many of the nation's largest health plans. Any vendor offering to sell a drug at or below the DPI price may be providing a good value for consumers.