Medicaid formularies: a critical review of the literature.

Studies on the impact of restricted Medicaid formularies were reviewed to assess whether other drugs on the formulary were substituted for restricted drugs, the cost of the substitutes, whether the substitutes were therapeutically appropriate, whether restricted drugs continued to be prescribed, what incremental administrative costs accompanied restrictions, what indirect costs occurred and how the cost-effectiveness of pharmaceuticals impinged on the total cost of illness. The assumption that restriction of specific drugs results in savings in the drug costs proportional to prior usage was shown to be questionable, numerous studies found alternate formulary drugs to the restricted drugs being prescribed, or patients were paying out-of-pocket for denied drugs. There was a tendency for alternate drugs to be more expensive. Little information exists as to the incremental administrative costs of restricted formularies or the therapeutic appropriateness of substituted drugs. One study suggests that major shifts in costs occur due to restrictive formularies through substitution of more expensive services such as hospitalization in lieu of pharmaceuticals. It is concluded that restricting formularies leads to dynamic changes in the total Medicaid program of a complex and often costly nature. Plans to implement formulary restrictions require considerable careful thought.