Ephedrine

Ephedrine is methamphetamine with a hydroxyl group on the beta carbon so it produces less of  a "rush" than speed (crosses the blood-brain barrier less readily). If you find  self-administering an amphetamine feels sleazy then don't do it.
___
  //  \\      CH3
 //    \\     |
 \      / CH2-CH-NH2     Amphetamine
  \    /
   ====
   ____
  //  \\      CH3
 //    \\     |
 \      / CH2-CH-NH-CH3  Methamphetamine
  \    /
   ====
   ____
  //  \\      CH3
 //    \\     |
 \      / CH2-CH-NH-CH3  Ephedrine
  \    /  |
   ====   OH

There are people who should NOT use the stack. It's a great supplement but not a magic bullet. During the first week of usage the user normally encounters a few small annoyances. Firstly, the the body is so stimulated byepinephrine and the boost to the CNS that they get a case of the "jitters". Their fingers shake mildly even though they are not agitated.

However, studies have shown that this effect recedes as time progresses (i.e. after the first week, it is not as apparent). This is, however, an important consideration for those who need steady hands in their occupation. This effect can be minimized. It is smart to ease into usage and not immediately start with heavy doses. For myself, I gradually started using the stack over two weeks, slowly working my way up to 5 days of the stack 3x a day. As a result, I did not notice "the jitters" as badly as people have when they just started popping the stuff like breath mints at a singles bar.  Furthermore, there is evidence showing that adding the amino acid tyrosine to the stack can minimize this effect. Adding 1 gram of L-tyrosine to the stack can help increase the effectiveness of the ephedrine by nearly 50%. What this implies is that you can reduce ephedrine dosages to half the normal dosage and thereby help curb off some of the stimulatory effect. Secondly, the stack can cause a bit of diarrhea if taken on an empty stomach, like creatine monohydrate.  This effect, however, can be minimized by taking the stack with a meal.  The diarrhea is mostly due to the caffeine - so if you are used to a bit of caffeine in your diet, then this might not even be a problem. However, taking the stack with a meal will ensure that the chemicals are buffered and are not as harsh on your stomach. 

Choose the optimal time of ingestion appropriate for you. Since the stack is stimulatory, it is not a smart idea to take a hit of it after 6:00 PM (assuming you're in bed by 11:00 PM). Remember that you can "feel" the stimulatory effects of the stack for a good 3-4 hours after taking it. Taking the stack too late in the night will keep you awake and restless when you normally go to bed.  Most people like a good night of sleep; so unless you're some kind of twisted nocturnal freak, don't take the stack too late in the night. Myself and others have noticed that after you cease your final dosage of ECA for the day, you do get a bit of a headache and do feel somewhat lethargic. The lethargy is easily explained. The ECA stack produces a stimulatory effect, so the body will try to maintain homeostasis by trying to balance out the stimulation with interaction from the parasympathetic nervous system. Since the stimulation is exogenous, i.e. of the body, once it is removed (i.e. ECA dosages are stopped), the parasympathetic system can operate unopposed - which is the reason why you feel tired. The headache is most probably a sign of caffeine withdrawal. Ephedrine itself does not seem to have any physiological withdrawal symptoms but if you are not to a certain amount of caffeine in your diet you might get a bit of a headache or feel irritable after ceasing dosages. In any event, a few Tylenol will easily take care of any headaches. It should be noted that headaches are not to be expected but do none the less occur occasionally. 

Ephedrine does raise blood pressure, but only temporarily. This is NOT a permanent effect (unlike eating excessive saturated fats in the diet). As soon as you cease usage, i.e. even in the same day, blood pressure returns to normal. It is not necessary to worry about negative impacts on blood pressure. 

You should not use ephedrine is you have heart disease, high blood pressure, thyroid disease, diabetes or an enlarged prostate. Furthermore, if you are taking any MAO inhibitor drugs for depression or appetite suppression, you should stay away from ephedrine. If you have peptic ulcers - aspirin and caffeine can aggravate that situation.