Expert system detection of drug interactions: results in consecutive inpatients.

Although drug interactions (DI) are a common cause of morbidity, their large number precludes remembering them. To address this problem, we constructed a microcomputer-based expert system and assessed its efficacy in 90 consecutive inpatients. It was found that, without the expert system, a knowledge of the patient's medication list did not affect the frequency of occurrence of DI. Also, without the expert system, no DI were predicted, clinically, whereas the expert system predicted 27 DI of which, in retrospect, 10 actually occurred. Unsuspected DI were most likely if: a drug was not within the specialty of the clinician, DI host factors were present, or the DI involved a commonly prescribed drug pair. Although none of the drug interactions were life-threatening, in two cases, the DI was the cause for admission. Since the offending medications could usually be adjusted in dose, drug interactions were easily corrected once clinicians were made aware of them.