Ephedrine and Caffeine work together to suppress appetite, increase heart rate, increase body temperature, and block the process of converting carbohydrates to fat (lipogenesis). Aspirin adds to this effect by thinning the blood, and also by telling the hypothalumus (which controls internal body temperature) that the increase in heat in the body is normal, hence decreasing the body's attempts to fight the increased body heat (which, in turn, leads to longer caloric burn).
When first taken, the stack will often cause a high due to the ephedrine (as it is a powerful stimulant, and is used as a precursor to amphetamine). Un-wise users believe that this high felt while first taking the stack means that the drug is working. When tolerance to the stimulant builds, users think that the drug has stopped working. This is, in fact, untrue. The stimulant effects subside, but the fat-burning effects do not.
If a user increases the dosage in order to obtain the high, side-effects can become dangerous and possibly lethal. Deaths caused by ephedrine