A single dose of a dietary supplement containing ephedra and caffeine can increase blood pressure and cause changes that have the potential to affect heart rhythms, according to a new study in the January 14 issue of The Journal of the American Medical Association (JAMA).
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 sessions, the two groups returned for the second phase of the study and received the other treatment. The participants' heart rate and blood pressure were monitored immediately before taking the supplement or placebo and 1, 3, and 5 hours after.
"Individuals receiving the dietary supplement containing ephedra and caffeine had a longer maximal QTc interval (mean [average], 419.4 versus 396.1 milliseconds) and higher systolic blood pressure (mean, 123.5 versus 118.93 mm Hg [millimeters/mercury] compared with placebo," the authors report.
"Overall, 53 percent of participants had QTc intervals increases of at least 30 seconds while taking the dietary supplement containing ephedra and caffeine." The authors note that the European Center for Proprietary Medicinal Products recognizes a drug-induced increase in the QTc interval of at least 30 milliseconds as a possible cause of concern in developing a potentially fatal irregular heart beat, known as torsade de pointes. The Food and Drug Administration has no official standards on QTc interval prolongation; however, the authors point out that the FDA has removed drugs from the market with lower QTc interval increases.
In conclusion the authors write, "The ephedra- and caffeine-containing dietary supplement Metabolife 356 increased the mean maximal QTc interval and systolic blood pressure. Since the actual ingredient or ingredients in Metabolife 356 responsible for these findings are not known, patients should be instructed to avoid this and similar dietary supplements until more information is known about their safety." (JAMA. 2004;291:216-221. Available post-embargo at JAMA.com)
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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