Principles for evidence-based drug formulary policy.

Expenditures for prescription drugs continue to increase, prompting insurers and health systems to adopt formulary or coverage policies restricting the use of more expensive drugs. Those establishing formulary policies face a complex array of claims regarding differences in efficacy, safety, treatment cost, or cost-effectiveness. We describe and illustrate 5 specific principles for applying research evidence to formulary decisions: (1) Experimental data should take precedence over models or simulations, and assumptions of such models should be carefully examined. (2) Morbidity or mortality outcomes should take precedence over surrogate or intermediate outcomes. (3) Claims for advantages of new treatments should consider the full range of alternatives rather than those selected by industry. (4) Variation in effects across individuals or subgroups argue against restrictions on first-line treatment, but only if those differences are predictable. (5) Variation in effects argues against requiring changes in ongoing treatment. We also discuss how economic incentives are likely to influence selection of research questions, especially research related to drug-gene interactions and to identifying new indications for existing drugs.