A rapidly emerging strategy in Medicaid's management of state budgetary shortfalls has been the creation of the preferred drug list (PDL) for the prescription of psychiatric medications. The list maneuvers doctors toward less expensive medications that the state considers to be equally effective. This year 22 states have used a PDL—up from three states just two years ago.

Typically, when clinicians, administrators, and regulators review the evidence base and Medicaid use patterns for psychiatric medications, they conclude that all the agents are equally effective and eliminate the most expensive ones from the PDL. Medicaid administrators usually control the reviews, although sometimes—but not always—outside expertise and opinion are included.

Medicaid reviews of psychiatric medications are well intended and focus on available evidence, but they are severely limited because of what is not known. We don't know the impact of drug acquisition costs on the total treatment costs or on the quality of life of the recipients and their loved ones. We don't know how these agents compare with each other over the long term. Most important, we don't know which patient will best respond to which drug.

Although we need to consider practical ways of avoiding wasteful spending on psychiatric medications, using PDLs for patients with severe mental illness is premature. Given the observed effectiveness of all types of psychiatric medications and our limited knowledge of which medication is most appropriate for which patient, patients should have access to all medications. Last year the American Psychiatric Association joined a coalition with the National Alliance for the Mentally Ill and the National Mental Health Association to advocate for open access to psychiatric medications.

If we do use PDLs, we should acknowledge that we are rationing medications. Rationing is an unfortunate policy, but we'd best start to get used to it. If rationing occurs, it should always be a public and societal event. We need best-practice models to ensure transparency in decision making and public accountability for the quality of care that ensues from all rationing decisions. Payer reviews must include completely independent parties, and the procedures that accompany rationing decisions should be crystal clear to all stakeholders. We need long-term comparative studies to inform us, so that we can make sound scientific decisions about the use of these medications. Twenty-two states have rushed to employ PDLs and more are considering it. I hope that the states consider the potential consequences of their decisions: are we hurting patients or inflating costs? For more background, see my Web site: www.medaccessonline.com.