Effects of restrictive formularies in the ambulatory care setting.

OBJECTIVE: To determine the consequences of restrictive formularies in the ambulatory care setting in 4 areas: overall drug expenditures, overall healthcare spending, changes in the quality of prescribing, and health outcomes. STUDY DESIGN: A MEDLINE search was conducted for English and French language articles, published between 1977-1999, that presented results in quantitative terms. Only articles from industrialized countries were used. METHODS: Information was extracted from each article in the following areas: time period of the study, geographic location and group of patients involved, outcome measurement(s), intervention, study design, and results. RESULTS: Poor methodologic quality made definitive conclusions difficult to draw in most areas. Prior authorization may be effective in controlling drug costs without increasing costs in other areas. Both desirable and undesirable therapeutic substitutions may take place when drugs are delisted from formularies. CONCLUSIONS: The use of restrictive formularies in the ambulatory care setting requires more rigorous research. Before changes are made in formularies, money needs to be set aside for research into short-term and long-term consequences of using restrictive formularies.