The ECA stack is a drug combination used in weight loss and as a stimulant. ECA is an initialism for ephedrine, caffeine, and aspirin, with variants of it including the EC stack, which removes the aspirin for those who can not tolerate it. Dietary supplements based on or including elements of ECA were popular through the 1990s and early 2000s, but the marketing of ephedra- or ephedrine-containing stimulant combinations for weight loss and bodybuilding is now restricted or illegal in the United States, Canada and Netherlands due to reports of heart attack, stroke, and death associated with these supplements
While it was available as a supplement, ECA was marketed with claims that it would aid weight loss, improve athletic performance and increase energy. Placebo-controlled studies have consistently found ephedrine in combination with caffeine to be effective in promoting moderate fat loss in the already-obese. A meta-analysis combining results from all available studies estimated average weight loss of 1 kg/month more than placebo. There is insufficient evidence to support use of ephedra for athletic performance.
Natural supplements that contain ephedra (aka Ma Huang) as an ephedrine substitute have been linked to cases of heart attack, stroke, and death in healthy young adults even when taken at the labeled dosage. A 2003 meta-analysis of all available studies and case reports concluded that: “ephedrine- and ephedra-containing dietary supplements […] have harms in terms of a 2- to 3-fold increase in psychiatric symptoms, autonomic symptoms, upper gastrointestinal symptoms, and heart palpitations. More serious adverse effects from ephedra use cannot be excluded at a rate less than 1.0 per thousand, and case reports raise the possibility that a causal relationship with serious adverse events may exis