Potential interactions between prescription drugs and complementary and alternative medicines among patients in the emergency department.

Study Objective: To determine the nature and prevalence of potential interactions between prescription drugs and complementary and alternative medicines (CAMs) and the reasons some patients do not advise their physicians of CAM use.

Design: Cross-sectional survey.

Setting: The emergency department of the Royal Melbourne Hospital, a tertiary referral center.

Patients: Four hundred four adult patients (>or= 18 yrs) who visited the emergency department between February 1, 2002, and March 31, 2003. Intervention. A specifically designed, self-administered questionnaire, available in seven languages.

Measurements And Main Results: Main outcome measures were the prevalence of potential prescription drug-CAM interactions and the reasons some patients do not advise their physicians of CAM use. Mean +/- SD patient age was 50.6 +/- 20.0 years; 220 patients were men (54.5%, 95% confidence interval [CI] 49.5-59.4%). When asked about use during the previous year, 275 patients (68.1%, 95% CI 63.2-72.5%) reported having taken a CAM; of these, 138 were also taking a prescription drug. We identified 15 documented potential drug-CAM interactions in nine patients (3.3% of CAM users, 95% CI 1.6-6.3%) and 97 theoretical potential drug-CAM interactions in 51 patients (18.6% of CAM users, 95% CI 14.2-23.8%). Aspirin and warfarin were the most commonly involved drugs. Of CAM users, 197 (71.6%, 95% CI 65.9-76.8%) never informed their physician about CAM use, most frequently because they were not asked.

Conclusion: The prevalence of potential drug-CAM interactions among patients in the emergency department is considerable, and some of these interactions could be clinically significant. Practitioners should increase their awareness of potential drug-CAM interactions, and education initiatives aimed at encouraging patient-physician discussion of CAM use are recommended, such as a CAM history in their patient evaluation. Further research is required to better determine the clinical significance of drug-CAM interactions.