Relationship between pharmaceutical services characteristics and exposure rates to drug-drug interactions in Veterans Affairs medical centers.

PURPOSE

The association between the exposure rates of clinically important drug-drug interactions (DDIs) and the structure of pharmaceutical services within the ambulatory care settings of Veterans Affairs medical centers (VAMCs) is discussed.

METHODS

The structure of pharmaceutical services in VAMCs was assessed using a questionnaire that was distributed by mail to chief pharmacists at 182 facilities. The questionnaire focused on the total volume of prescriptions dispensed at each VAMC, the level and characteristics of pharmacy staffing, the characteristics and distribution of available pharmaceutical services, the availability of specialty ambulatory clinics, and the extent of clinical pharmacist coverage within these clinics. A list of 25 clinically important DDIs that were most likely to be encountered in ambulatory care settings was used in this study. Multivariate regression was used to assess the relationship in the structure of pharmaceutical services and the exposure rate to clinically important DDIs.

RESULTS

A total of 790,541 patients were treated by the 52 VAMCs included in this study, with a total of 17,447 patients exposed to DDIs of interest. VAMCs with a lower prescription volume, a higher number of pharmacists in ambulatory care settings, and a higher number of ambulatory specialty clinics had significantly lower rates of potential DDIs.

CONCLUSION

Exposure to clinically important DDIs was significantly lower in VAMCs with a higher number of pharmacists in ambulatory care settings, a higher number of ambulatory specialty clinics, and facilities with lower prescription volumes.