Drug interaction exposures in an ambulatory Medicaid population.

The incidence of selected potential drug-drug interactions (DDIs) in a population of ambulatory patients was studied using data extracted from the automated records of Medicaid drug benefit programs. The system to extract DDI data was devised to assist peer review committees in drug use review. The system yields two types of reports: (1) individual patient profiles and (2) summary reports of all potential DDIs detected within the Medicaid population being reviewed. Potential drug interactions are classified as major, moderate or minor and by route of drug administration. Three months of drug claims from two Medicaid programs were reviewed for potential DDIs involving digitalis preparations, antihypertensive agents (rescinnamine, deserpidine, guanethidine, methyldopa, reserpine, Rauwolfia serpentina extracts) and coumarin anticoagulants. The overall incidence of potential DDI exposures for the three classes was 2.7%, based on drug profiles of 333,641 patients. DDI exposure monitoring can be a useful tool in acquiring further knowledge of DDIs occurring in ambulatory patients.