Clenbuterol is known as a sympathomimetic. These hormones are taken to mimic adrenaline and noradrenaline in the human body. Clenbuterol is a selective beta-2 agonist that is used to stimulate the beta receptors in fat and muscle tissue in the body. Clenbuterol exhibits most of it's effects on the stimulation of both type 2 and 3 beta receptors. Clenbuterol is really one of bodybuilding's most misunderstood performance enhancement drugs. It is often been stated that clenbuterol is effective in causing anabolic gains and has in times even been compared to some of the weaker anabolic steroids. Books such as the World Anabolic Review, 1996, by P. Grunding and M. Bachmann state incorrectly that, "its effects, however, can by all means be compared to those of steroids." These statements are inaccurate and misleading to say the least. A lot of these claims as to the anabolic effects of clenbuterol are derived from studying the effects of clenbuterol on livestock. Clenbuterol is effective in increasing muscle mass and decreasing fat loss in animals. The problem with the variation in anabolic effects between humans and livestock is that livestock have an abundance of the type 3 beta receptors whereas humans have little if any of the type 3 beta receptors. These beta-3 receptors increases insulin secretion and sensitivity, causing more glucose and amino acids to be transported into skeletal muscle thus causing the anabolic effects that we, humans, just aren't seeing. As Dan Duchaine stated in his Muscle Media article on clenbuterol, "In those animal research studies showing an anabolic effect from clenbuterol, it's my guess the anabolism happens specifically when the beta2 receptor stops working. At that point, the beta3 increases and causes the anabolic effect through insulin mechanisms." Since humans, again, have either very little or no beta-3 receptors, there is no chance of this anabolic effect. Just another of the studies where everyone assumed that what works in animals must work in humans. This is just simply not the case with clenbuterol.
Side effects of clenbuterol include:
Muscular tremors (especially hand shakes)
Hypertension (high blood pressure)
Possible cardiac hypertrophy as clen also targets cardiac and smooth muscle fibres
Heart muscle necrosis has been demonstrated in animal studies
Clen can have some serious side effects (like sudden death) at very high dosages. Clen is very hard on your system.