Evaluation of a limited drug formulary in an adult internal medicine clinic.

The utility of a 30-drug, limited formulary in an adult internal medicine, ambulatory-care clinic was investigated. The formulary was developed using a mail survey of a random sample of members of the ASHP Ambulatory Care Pharmacy Practice Special Interest Group. The consensus formulary comprised the 30 most frequently recommended drugs; the utility of the formulary was then tested by chart review in a primary-care internal medicine clinic. Over a two-month period, the charts of alternating patients were reviewed daily; patient data collected included demographic information and prescribed drug therapy. A panel of two physicians and one pharmacist reviewed each patient's data and determined the appropriateness of drug treatment. If an agent was prescribed that was not on the consensus formulary, the panel determined whether an appropriate formulary agent could have been prescribed. Of the prescribed drug orders, 57.8% were for agents in the consensus formulary; by including patients who could have received formulary drugs appropriately, 73.7% of all prescription orders were or could have been for formulary drugs. Age, race, and sex of patients had no significant effect on utility of formulary agents. Had the 30 drugs most commonly prescribed in this clinic been in the formulary, 82.6% of all prescription orders would have been covered. This approach to establishing a new formulary and selecting drugs for inclusion is potentially useful.