unless something has changed on me over the years, ECA is nothing more than a combination of Ephedrine, Caffeine, and Asprin.
The Ephedrine works as the thermogenic effect, boosting metabolism.
The body fights that increase and try's to normalize the metabolism, so the Caffeine slows that down.
The Asprin prolongs the effects.
If you have blood pressure or heart issues be careful. My girlfriend tried a stack, while walking on the treadmill her heart rate would race up into the 190's. She is very sensitive to medication.