• Brian F McBride, Angeliki K Karapanos, Agnes Krudysz, Jeffrey Kluger, Craig I Coleman, and C Michael White.
• University of Connecticut Schools of Pharmacy, Storrs, Conn, USA.
• JAMA. 2004 Jan 14; 291 (2): 216-21.

ContextMetabolife 356, a multicomponent dietary supplement containing ephedra and caffeine (DSEC) in addition to several other components, is the top-selling dietary weight loss supplement. Given its common use, anecdotal reports of cardiovascular and cerebrovascular adverse events, and paucity of safety data, further research with this DSEC was warranted.ObjectiveTo determine the impact of the DSEC on corrected QT (QTc) interval duration and systolic blood pressure (SBP).DesignRandomized, double-blind, placebo-controlled, crossover study conducted from January to May 2003.Setting And ParticipantsFifteen healthy volunteers (mean [SD] age, 26.7 [2.52] years; weight, 72.7 [14.93] kg), 6 (40%) of whom were women, recruited from the University of Connecticut, Storrs campus.InterventionA single dose of the DSEC (containing 19 ingredients including ephedra [12 mg] and caffeine [40 mg]) or matching placebo were administered in a crossover fashion with a 7-day washout period between treatments.Main Outcome MeasuresMaximal QTc interval and SBP assessed at 1, 3, and 5 hours after dosing for the DSEC relative to placebo.ResultsIndividuals receiving the DSEC had a longer maximal QTc interval (mean [SD], 419.4 [11.8] vs 396.1 [15.7] milliseconds; P<.001) and higher SBP (mean [SD], 123.5 [10.98] vs 118.93 [9.62] mm Hg; P =.009) compared with placebo. Participants who received the DSEC were more likely to experience a QTc interval increase of at least 30 milliseconds vs placebo (8 individuals [53.3%] vs 1 individual [6.7%]; relative risk, 2.67 [95% confidence interval, 1.40-5.10]). There were no significant sex-related differences.ConclusionsThe ephedra- and caffeine-containing dietary supplement Metabolife 356 increased the mean maximal QTc interval and SBP. 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.

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