Evaluating drugs after their approval for clinical use.

The most common therapeutic intervention in medicine is the writing of a prescription1. The proliferation of therapeutic alternatives and the growing recognition of the clinical and economic consequences of suboptimal pharmacotherapy2–4 have stimulated a variety of efforts to improve prescribing. These include physician-education programs,2,3 required drug-utilization review for patients covered by Medicaid,5 restrictive access policies (formularies, service limitations, requirements for prior approval, and substitution requirements),6 and direct federal regulation of the indications for using prescription drugs7. However, physicians, third-party payers, and regulators must face a fundamental but rarely asked question: Are there adequate data to guide . . .