Formulary limitations and the elderly: results from the Managed Care Outcomes Project

To examine whether restrictive formularies are associated with differences in healthcare resource utilization, including number of office visits, prescriptions, and hospitalizations, and whether this association varies by age.

Cross-sectional, longitudinal study.

Patients enrolled in one of six health maintenance organizations in six different states, three in the eastern and three in the western United States, were eligible for the study. Data from between 1309 and 3938 patients were available for analysis for each of the five diseases studied, for a total of 12,997 patients across all study diseases. Healthcare utilization by patients in the study included more than 99,000 office visits, 1000 hospitalizations, and 240,000 prescriptions. We used severity-adjusted prescription counts, prescription costs, office visit counts, and measures of inpatient hospital utilization to assess the effects of formulary limitations.

We found positive, significant associations between the independent variable formulary limitations in drug class and the dependent variables measuring resource utilization. These associations were sometimes significantly greater for elderly patients after controlling for severity of illness and other variables.

Common strategies for decreasing drug expenditures may be associated with higher severity-adjusted resource utilization. In specific areas, this association is more pronounced in the elderly.