Appropriateness of medication prescribing in ambulatory elderly patients

To assess the quality of medication prescribing in ambulatory elderly patients on multiple medications using the Medication Appropriateness Index (MAI).

Cross-sectional study.

General Medical Clinic of the Durham VA Medical Center.

208 elderly outpatients on five or more regularly scheduled medications.

Medication prescribing appropriateness was measured with the MAI, a reliable method that employs 10 implicit criteria. A weighted MAI score (range 0-18 per drug) served as a summary measure of appropriateness.

There were 1644 medications evaluated; 26% received no inappropriate ratings, 37% had one, 19% had two, and 18% had three or more. Of 16,440 ratings, 2295 (14%) were evaluated as inappropriate. The percentage of inappropriate ratings varied across prescribing dimensions: drug-drug interactions, 0%; drug-disease interactions, 1.4%; medication effectiveness, 4.7%; therapeutic duplication, 5.7%; indication, 11.5%; duration of treatment, 16.5%; dosage, 17.3%; practical directions, 20.3%; cost, 29.7%; and correct directions, 32.4%. The mean MAI score for all medications was 2.2 +/- 2.1 (range 0-10) and varied by therapeutic class. MAI scores were significantly lower for medications with a high potential for adverse effects compared with those with a low potential (MAI score of 1.8 vs 2.9, P < 0.001). Regression analysis revealed that no patient characteristics were associated with a higher likelihood of inappropriate prescribing.

Medication prescribing for elderly outpatients taking multiple medications was substantially appropriate. Prescribing dimensions with the most room for improvement were more exact directions, less expensive drugs, and practical directions. Drugs at high risk for adverse effects were prescribed more appropriately than those at low risk.