According to the authors of the study, which is published in Clinical Pharmacology & Therapeutics (June 2005; vol 77; no 6), research into the effects of ephedra is still relevant as FDA's 2004 final ruling banning its use in dietary supplements did not staunch the supply from all possible sources.
"Although ephedra is now banned as a dietary supplement ingredient, it can still be obtained as a traditional Chinese medicine, ma huang," they wrote.
"Synthetic ephedrine is also available as an over-the-counter medication [Primatene from Wyeth Pharmaceuticals] for asthma and can be obtained as an energy-boosting product in convenience stores and via Internet distributors of performance-enhancing supplements."
They also said that safety studies of dietary supplements containing herbal stimulants are of interest, as some weight-loss products have been reformulated with combinations of herbal caffeine and sympathomimetics like Citrus aurantium (synephrine) in place of ephedra.
What is more, in April a court in Utah ruled that the FDA had failed to meet its burden of proof that a daily dose of 10 mg or less of ephedrine alkaloids presents an unreasonable risk of illness or injury. The FDA is appealing the decision, which has prompted some sectors of the dietary supplements industry to claim the ban has been effectively overturned - even though trade associations have said there are no plans amongst their members to reintroduce ephedra products for the time being.
Although it has stirred up renewed debate over ephedra, the Utah ruling does not have a direct bearing on the new study, however, since the dose to which it applies is lower than that used in the trial.
The randomized, double-blind, 3-arm crossover study involved 16 healthy participants (eight men and eight women). Each one took either two doses of ephedra-guarana (23.3mg ephedra alkaloids and 167mg of caffeine), two doses of Xenadine RFA (25 mg ephedra alkaloids and 200 mg caffeine), or two doses of a placebo. The doses, which were consistent with the products' instructions, were taken five hours apart.
The researchers found that both Xenadrine and the ephedra-guarana increased heart rate by up to 18 beats per minute and systolic and diastolic blood pressure by up to 22.2 mm Hg and 14.7 mm Hg respectively.
Postprandial glucose concentration and insulin concentration also increased significantly, and serum potassium concentrations decreased.
While the metabolic and circulatory changes occurred after both the first and second doses, plasma free fatty acid concentrations only increased after the first dose.
"These findings provide further evidence that dietary supplements containing combinations of sympathomimetics could potentially have unfavorable cardiovascular effects, particularly in individuals with underlying hypertension, glucose intolerance, or atherosclerosis," concluded the researchers.
The anti-ephedra camp has argued that the herbal also poses a risk to apparently healthy people, citing the sudden death of 23-year-old professional baseball player Steve Belcher in 2003. The coroner's report gave the cause of his death as heat stroke but said that Xenadrine, which was reportedly found in his locker, was a contributing factor.