Effect of a multicomponent, ephedra-containing dietary supplement (Metabolife 356) on Holter monitoring and hemostatic parameters in healthy volunteers

Abstract

Herbal products containing ephedra (a natural source of ephedrine alkaloids) in combination with other ingredients exhibiting sympathomimetic properties (kola nut, guarana, and green tea extract) are widely available under names such as Xenadrine RFA-1 (Cytodyne Technologies, Lakewood, New Jersey), Metabolife 356 (Metabolife International, San Diego, California), and Ripped Fuel (Twin Laboratories, Inc., Hauppauge, New York). These products are most often taken to promote weight loss and to enhance exercise performance. Metabolife 356 has become the nation’s best-selling weight loss supplement, capturing 45% of the weight loss supplement market. Metabolife 356 contains a variety of herbs, including ma huang, guarana, ginger, ginseng, and gotu kola, as well as various other vitamins and minerals. Only a few studies have evaluated the effectiveness of ephedra-containing products on weight loss, yet the safety aspects of these products remains equivocal. Ephedracontaining dietary supplements have been associated with serious adverse effects, including myocardial infarction, cardiac arrhythmia, hypertension, hepatitis, seizure, stroke, and death. 1– 8 This study was conducted to evaluate the short-term effects of Metabolife 356 on blood pressure, heart rate, 24-hour Holter monitoring, and hemostatic parameters in healthy subjects.  Healthy men aged 20 to 40 years were included in this study. Exclusion criteria were history of consumption of any ephedra-containing supplement, any known medical condition, smoking, and current use of any prescription or nonprescription medication. Subjects were required to refrain from caffeine and exercise throughout the study period. The protocol was approved by the institutional review board. All subjects provided written informed consent before any study-related procedures were initiated. After a 7-day, caffeine-free period, subjects underwent baseline venipuncture, cuff blood pressure measurement, heart rate, 12-lead electrocardiography, and physical examination. Casual cuff blood pressures were measured using an aneroid sphygmomanometer in the dominant arm after a minimum of 10 minutes of rest in a seated position. After confi rmation of a 12hour fast, venous blood samples were collected and the serum was separated and stored frozen at 70°C. The samples were shipped frozen to the clinical laboratories and were analyzed for tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) using enzyme-linked immunosorbent assay; ephedra was assessed using liquid chromatographic/ mass spectrophotometric techniques. A baseline chemistry panel and complete blood count were also obtained to rule out any abnormalities before supplementation. Subjects with normal fi ndings at the baseline visit