tient office visits during 1995–1996 to 49 percent of office visits during the 2001–2002 (Roumie et al., 2005). The general issue of overuse of medications in patients with other conditions is also undoubtedly important, but this is perhaps the best-documented case.
In an effort to control the costs of pharmaceuticals, managed care organizations have established formularies—schedules of prescription drugs that will be paid for by a health insurance plan and dispensed through participating pharmacies. Often patients taking prescription drugs switch from one managed care organization to another, resulting in the need to switch to another formulary. This sometimes involves patients changing their medications. Moreover, there can be difficulties in the handoffs between managed care organizations, which can result in patients having periods of time off their medications. Formulary changes may also be required when a patient moves from an outpatient to an inpatient and then back to an outpatient setting. In this situation, a recent study found a minimal effect of the hospital formulary on postadmission use of proton pump inhibitors and statins as compared with pre-admission use in a privately insured managed care population (Sun et al., 2005).
Limited research has been carried out on the impact of the use of formularies and formulary switching on medication safety. A major review of studies of interventions to improve drug use in managed care organizations found evidence for the effectiveness of several interventions but little understanding of longer-term efficacy and safety issues (Pearson et al., 2003). An editorial in a psychiatric journal commented that Medicaid preferred drug lists had been rapidly implemented across the nation, but studies analyzing the impact of these lists on patients had not kept pace (Elam et al., 2005). In the case of psychotropic drugs, however, concerns have been raised about the use of overly restrictive formularies. Studies have shown that the failure to respond to one selective serotonin reuptake inhibitor or the occurrence of severe side effects does not mean the patient will have the same experience with another such drug (Huskamp, 2003). The committee believes the impact of the use of formularies and formulary switching on medication safety is an area that requires further research.
The costs of medication errors have been much less well researched than incidence rates. The committee could find no studies on the costs of ADEs relating to pediatric and psychiatric care or to the use of OTC and