According to background information in the article, "Dietary weight-loss supplements often combine ephedra and caffeine with various other natural ingredients. In the United States, more than 3 billion doses of these herbal preparations are sold annually, resulting in $7 billion in sales," the authors write. "... consumers are drawn to herbal preparations because of their nonprescription status, direct-to-consumer advertising, and the perception that natural products are innately safe. Unfortunately, the perception of safety may be the result of a lack of data."
Brian F. McBride, Pharm.D., from the University of Connecticut Schools of Pharmacy, and colleagues evaluated the impact of Metabolife 356, the best-selling dietary supplement containing ephedra and caffeine, in addition to several other ingredients, on corrected QT (QTc) interval duration and systolic blood pressure. The QTc interval is a measure of the time intervals that occur during the electrical impulses that stimulate the heart to contract. A longer QTc interval can increase the risk of developing abnormal heart rhythms. Systolic blood pressure is the higher number of a blood pressure reading, representing the blood pressure when the heart is contracting.
Fifteen healthy volunteers with an average age of almost 27 years were recruited for this randomized, double-blind, placebo-controlled study conducted from January to May 2003. The individuals were randomized to receive either the dietary supplement containing 19 ingredients, including ephedra (12 milligrams) and caffeine (40 milligrams), or the placebo capsule (sugar pill) as their first treatment. With a week off between the treatment se
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