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Dietary Supplement Containing Ephedra and Caffeine Causes Electrocardiographic Changes and Increased Systolic Blood Pressure

A single dose of the dietary supplement, Metabolife 356, significantly prolongs corrected QT (QTc) interval and P-wave duration, and increases systolic blood pressure, say researchers.

"We studied young healthy volunteers without comorbid conditions and normal baseline QTc intervals rather than obese participants or those looking to enhance athletic performance," writes C. Michael White, PharmD, University of Connecticut Schools of Pharmacy, Storrs, United States, and colleagues.

In this double-blind, crossover study conducted from January to May 2003 at the University of Connecticut, the researchers randomised 15 participants to receive either the contents of 1 Metabolife 356 tablet, which contains 12 mg ephedra and 40 mg caffeine as well as 17 other ingredients and is the smallest standard single dose of the preparation, or matching placebo followed by a 7-day washout period before crossover. The 15 participants, (6 women) were a mean age of 26.7 years, a mean weight of 72.7 kg, and a mean body mass index of 24.1.

Overall, the Metabolife 356 group had a mean maximal QTc interval of 419.4 milliseconds compared with 396.1 milliseconds in the placebo group. This represents a 5.9% higher maximal QTc interval for the supplement group compared with placebo.

After supplement ingestion, 53.3% of the volunteers had a QTc interval increase of at least 30 milliseconds compared with a similar increase in 6.7% after ingesting placebo. Supplement ingestion resulted in a 17% higher P-wave duration, a 50% greater QTc interval dispersion, and a 40.4% greater P-wave dispersion compared with placebo. Supplement ingestion also resulted in a 4.8% greater maximum systolic blood pressure and a 7.9% greater stroke volume index compared with placebo.

Adverse events with Metabolife 356 use included sinus tachycardia at a rate of 120 beats per minute with palpitations in 1 volunteer, premature ventricular complexes in another volunteer, and one additional volunteer with hand tremor, but all conditions subsided within 1 to 5 hours after dosing. All participants reported nonspecific symptoms of jitteriness, queasiness, or not feeling quite right after taking the dietary supplement but no symptoms after taking placebo.

"This study demonstrated that a single dose of a dietary supplement containing ephedra and caffeine significantly prolongs the QTc interval and P-wave duration, risk factors for the development of ventricular and atrial arrhythmias, respectively," the authors conclude, adding "Systolic blood pressure is also increased." They suggest that Metabolife and similar products "be avoided" until further studies confer more information.

JAMA 2004;291:216-221.

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