In 2004, the U.S. Food and Drug Administration banned the U.S. sale of ephedra and its alkaloids, including ephedrine, due to safety concerns. Until that time, ephedrine was commonly combined with caffeine to make diet pills. In fact, the ephedrine/caffeine combination was shown to be very effective at promoting weight loss, even better than either chemical alone. That finding led to research that investigated the relationship between the two. It's not that caffeine makes ephedrine last longer, simply that they work better together than apart.
Thermogenesis
A 1991 study in the journal "Metabolism: Clinical and Experimental" investigated the way caffeine and ephedrine worked together to burn fuel. Researchers measured the effect of caffeine plus ephedrine against a placebo, and found that the combination produced a thermogenic effect greater than would be obtained with either caffeine or ephedrine alone, even at double the dose. The study did not reveal the nature of the mechanism, only its existence -- the ephedrine/caffeine combination at the 20 mg/200 mg dose burned an extra 10 calories per hour.
Muscle Retention
This thermogenic effect was what made the combination such an effective weight loss supplement -- an increased calorie burn leads to a more rapid weight loss, and caffeine is known to have mild appetite suppressing effects. A 1992 study in the journal "Metabolism: Clinical and Experimental" found that ephedrine plus caffeine resulted in an increase in calories burned, all of which came from fat. All study participants lost approximately the same amount of weight, but those given the ephedrine/caffeine combo lost 4.5 kg more fat and 2.8 kg less muscle. The fat loss was expected, but the preservation of muscle mass was a surprise that led to further research.
Performance Enhancement
A caffeine/ephedrine combination extends time to fatigue during anaerobic exercise, allowing you to work harder and longer at muscle-building workouts. This accounts for muscle mass preservation seen in weight loss studies, but the mechanism was still unclear. A 2001 study in the journal "Medicine and Science in Sports and Exercise" tested the effects of caffeine plus ephedrine against both caffeine and ephedrine alone. Ephedrine alone seemed to increase power early in the exercise session, while caffeine alone lengthened time to fatigue. Researchers concluded that the benefit of the combination comes from the ephedrine's ability to stimulate the central nervous system and caffeine's ability to increase contraction strength and reaction time of muscle fibers.
Dangers
The caffeine/ephedrine combination certainly proved to be effective, but that doesn't mean it's safe. Caffeine can cause nervousness, tremors and sleeplessness, and ephedrine comes with an even longer list of potential dangers. According to MayoClinic.com, possible ephedrine side effects include nausea, vomiting, abdominal pain, anxiety, dizziness, headache, hallucinations, delirium, fainting, depression, mania, seizures and stroke. In people with pre-existing cardiovascular disease, it can cause irregular heartbeat, fluid in the lungs and heart attack, and may also cause kidney stones, pain with urination and uterine contractions. This is why ephedrine is not to be used during pregnancy, but it also penetrates the placenta and causes increased heart rate in the fetus.
References
- "Sports Medicine"; Caffeine and Ephedrine: Physiological, Metabolic and Performance-Enhancing Effects; Magkos F, et al.; 2004
- "Metabolism: Clinical and Experimental"; Thermogenic Synergism Between Ephedrine and Caffeine in Healthy Volunteers: A Double-Blind, Placebo-Controlled Study; Arne Astrup, et al; March 1991
- "Metabolism: Clinical and Experimental"; The Effect of Ephedrine/Caffeine Mixture on Energy Expenditure and Body Composition in Obese Women; Astrup A, et al.; July 1992
- "Medicine and Science in Sports and Exercise"; Effect of Caffeine and Ephedrine Ingestion on Anaerobic Exercise Performance; Bell DG, et al.; August 2001
- MayoClinic.com: Ephedra (Ephedra sinica)/ Ma Huang
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