Use of Dietary Supplements by Patients Taking Digoxin: METHODS

19 Nov

Study Design and Setting

This open-label, cross-sectional survey study was approved by the University of British Columbia/ Providence Healthcare Research Ethics Board. Patients receiving digoxin therapy were recruited at St Paul’s Hospital, Vancouver, British Columbia, a 500-bed urban teaching hospital.


For the purposes of this report, OTC medications are defined as medicinal products that are sold without a prescription. Examples include antacids, kaolin-pectin, quinine, and acetylsalicylic acid. The term “herbal supplements” is used for oral botanical supplements such as herbs and herbal extracts that are sold without a prescription. Examples include aloe, ginseng, and licorice root. Nonherbal supplements are vitamins, minerals, potassium supplements, and other nonherbal dietary substances. The term “dietary supplements” includes both herbal and nonherbal supplements, and the term “nonprescription medications” is used to refer collectively to both OTC medications and dietary supplements. buy kamagra

Study Population and Recruitment

Potential study participants were identified by reviewing charts from the cardiology, general medicine, renal, and vascular wards and the Healthy Heart Clinic (a cardiac rehabilitation clinic) of St Paul’s Hospital. Patients were included if they were at least 19 years old, had obtained their prescription medications in British Columbia, had been taking digoxin as an outpatient for at least 3 months, were fluent in English, had provided informed consent, and were able to participate in an in-person or telephone interview. The study sample size, which was one of convenience, was determined by the number of patients that could be recruited between June 2001 and November 2003.

Three interviewers (including E.N.) contacted potential participants to explain the purpose of the study, without mentioning the emphasis on use of nonprescrip- tion medications. Patients were told that the interview would include questions about use of medications, both prescription and nonprescription, and diseases that might influence the effects of digoxin. Patients who were in hospital at the time they were identified as potential participants were contacted in person; outpatients initially received a letter from the primary caregiver, and the interviewer followed up by telephone.
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