Use of Dietary Supplements by Patients Taking Digoxin

Background: The use of dietary supplements is common, and interactions with digoxin have been proposed. However, little is known about usage patterns of these supplements among patients taking digoxin. Objectives: To determine the prevalence of use of dietary supplements and over-the-counter (OTC) medications among patients taking digoxin, and to correlate the occurrence of symptoms related to digoxin toxicity with supplement use. Methods: One hundred and seventy-two adult patients who had been receiving digoxin therapy for at least 3 months were recruited. An open-label, cross-sectional, interviewer-administered survey was conducted to assess demographic characteristics, health status, details of digoxin therapy, and use of prescription and nonprescription medications. The use of supplements and interacting prescription medications was compared between participants reporting symptoms of digoxin toxicity and those who did not report such symptoms. Results: Most of the patients (122 or 70.9%) were men; the mean age +/- standard deviation was 65.2 +/- 12.0 years, and patients had been taking digoxin for a mean of 5.9 years at 174.8 +/- 77.9 mu g/day. Thirty-seven (21.5%) of the patients were using herbal supplements, and 153 (89.0%) were taking OTC medications or nonherbal supplements. Four (2.3%) patients were taking herbal supplements that might interact with digoxin, and 50 (29.1%) took OTC drugs or nonherbal supplements with potential interactions. Between patients who reported symptoms of digoxin toxicity and those who did not reports such symptoms, there was no difference in the use of OTC medications or nonherbal supplements, herbal supplements, or prescription medications (except for diltiazem). Conclusions: In this study, few of the patients were taking herbal supplements that could interact with digoxin, and no clinically significant herb-digoxin interactions were observed.