Suboptimal prescribing in elderly outpatients: potentially harmful drug-drug and drug-disease combinations.

OBJECTIVES

To assess the prevalence and correlates of potentially harmful drug-drug combinations and drug-disease combinations prescribed for elderly patients at outpatient settings.

DESIGN

Retrospective analysis of the 1995-2000 National Ambulatory Medical Care Survey (NAMCS) and the National Hospital Ambulatory Medical Care Survey (NHAMCS).

SETTING

Physician offices and hospital outpatient departments.

PARTICIPANTS

Outpatient visits by patients aged 65 and older in the NAMCS and NHAMCS (n=70,203).

MEASUREMENTS

Incidences of six drug-drug combinations and 50 drug-disease combinations that can place elderly patients at risk for adverse events according to expert consensus panels.

RESULTS

Overall, 0.74% (95% confidence interval (CI)=0.65-0.83) of visits with two or more prescriptions had at least one inappropriate drug-drug combination, and 2.58% (95% CI=2.44-2.72) of visits with at least one prescription had one or more inappropriate drug-disease combinations. Of visits with a prescription of warfarin, 6.60% (95% CI=5.46-7.74) were prescribed a drug with potentially harmful interaction. Of patients with benign prostatic hypertrophy, 4.06% (95% CI=3.06-5.06) had at least one of six drugs that should be avoided. The number of drugs prescribed is most predictive of inappropriate drug-drug and drug-disease combinations.

CONCLUSION

Potentially harmful drug-drug and drug-disease combinations occur in various degrees in outpatient care in the elderly population. Targeting combinations such as those involving warfarin that are high in prevalence and potential harm offers a practical approach to improving prescribing and patient safety.