Answer:

First off, be aware that ephedrine and caffeine in combination has been shown to cause side effects such as rapid pulse, raising blood pressure, nervousness, sleeplessness, and in extreme cases where people are especially sensitive to it, loss of memory and passing out.

It may be better to try other supplements before using this combination (I actually don't recommend using it).

How long caffeine and ephedrine keep your blood pressure raised depends on a number of factors but generally the effects diminish after about 4 to 6 hours after taking it. The greatest factor that affects this is the dosage you take. The more you take, the longer it will take to decrease the effects (up to a point).

Some people are especially sensitive to the stimulating properties of ephedrine and experience this for longer periods. Some tolerate the combination quite well.

It is also generally accepted that the longer you take ephedrine, the more accustomed your body becomes to it and the faster the effects will diminish.