In terms of action this drug is best likened to the now also illegal ephedrine and its legal replacement, ma huang. All of them operate mainly by increasing the manufacture and secretion of catabolic hormones known as cathecholamines (like dopamine, epinephrine (adrenaline) and norepinephrine (noradrenaline)) which are secreted from the adrenal region. Now these hormones have a wide variety of functions. First of all they seem to alter the contractile characteristics of smooth muscle, but very specifically.
Some will apparently be stimulated, and others inhibited. Amongst those inhibited, the smooth muscles in the bronchial tree, which explains its soothing effect in patients with breathing problems. What it also does is increase thermogenisis. This usually encompasses a rise in blood pressure, a stimulatory effect of the heart muscle and a resulting rise in body temperature.
Along with the reversing of the effects of insulin (and inhibiting the action of insulin) which results in a release of glycogen back into the blood stream as glucose and an inability to store or use more glycogen, it will increase the rate of protein and fat being burned in the body. For bodybuilders that appears to be the primary use of the drug. This thermogenisis and an increase in the rate of fat being burned usually has as a result that the metabolic rate of the subject its much higher and he burns more calories. This in turn results in loss of adipose tissue (the shedding of fat in other words) revealing a leaner physique with cuts and striations. The downside to this effect is that there is a concomitant rise in the rate of protein being burned. Where fat is robbed from the fatty tissue in the body, protein is generally robbed from the muscle. As with all catabolic hormones, in time muscle loss can and will occur. Which is why many opt to use this compound during a cycle of anabolic steroids that will help preserve the lean body mass while reducing the fat.
Among the other actions that cathecholamines have is an increase in aerobic capacity (facilitated by the easier breathing), a stimulation of the nervous system (facilitated by norepinephrine and acetylcholine release) and thus the skeletal muscle system, an increase in oxygen transportation (facilitated by the increased blood pressure) and an increase in vigil. These characteristics in turn combine to make this drug particularly interesting for athletes doing endurance sports and needing a boost. Especially in middle-long running numbers, this drug is widely abused and its no secret that in cycling circles clenbuterol in liquid form is combined with a painkiller and the drug EPO (synthetic erythropoeitin, a renal hormone) which increases the manufacture of red blood cells. It is then injected along the road, thereby avoiding positive tests prior to the race. Needless to say such a cocktail is very hazardous to the cardiovascular system. Just to demonstrate the wide use of this drug and its immense popularity among athletes, observe the US Olympic team. Exercise-induced asthma is an afflmiction that generally occurs in 3-7% of the population, and is in some rare cases treated with clenbuterol. In 2000 60% of US Olympic athletes claimed to have exercise-induced asthma and ALL of them were prescribed clenbuterol for this condition. An otherwise illegal drug, tolerated solely for this reason. And this while the Romanian gymnast Andrea Raducan was stripped of her gold medal for the 25 µg of norephedrine in her cold medicin she was taking...
In several animal studies1,2,3 Clenbuterol was also shown to act as an anabolic, believed to be able to impart muscle gains. This was never demonstrated in humans4 however, and there is more evidence that its effect on catabolic hormones invokes the opposite. In any case, the animal studies used much higher doses5 then one would safely recommend for humans. The late Dan Duchaine, by many held in high regard as a steroid guru and a former writer of the now defunct MM2K, believed it had something to do with the stimulation of a third beta receptor, which was different in humans as opposed to other mammals, and that this was the reason humans did not receive any anabolic benefits. As with most of what Dan said, this is very questionable, but one of many possible explanations in a debate that still rages on. Despite the many claims of other bodybuilders that still swear it has some form of anabolic action, I must say I've seen enough proof to the contrary to strongly advise against buying clenbuterol for promoting muscle mass. You may be more than sorely disappointed. Next time you see a 230 pound, 6 foot top-level cyclist, let me know and I may change my mind.
Clenbuterol, when used for its fat-burning properties is best used in a pyramid scheme. Slowly building up the dose may be more important that tapering off of it, as most first time users will rarely if ever know how they will react. Because of the effects on blood pressure its best to start with 20-40 µg per day and slowly work your way up increasing the dose every 3 days by 20 µg, to a maximum of 120-160 µg (most find 80 µg to be adequate). Its also best not used for long periods of time. Body homeostasis seems to negate the excitatory and inhibitive functions of clenbuterol over time, creating a complacency effect. It loses most of its nerve stimulation and fat burning benefits after 3-4 weeks, and using it longer on end would be futile. The user is best to discontinue use for an equal period of time and then recommence again.
Another thing people should be aware of is the inherent liver toxicity associated with clenbuterol use. When stacking with oral 17-alpha-alkylated steroids, accutane, anti-biotics or other hepatoxic elements, one should have his liver values checked by a licensed physician at regular points in time to avoid all problems. If you not a yellow discoloration of the skin cease use immediately and contact your doctor.
Clenbuterol should be built up and tapered off gradually with dosage increases and decreases every 3-4 days and doses never exceeding 160 µg per day to be perfectly safe. Its mostly used for periods of 2-3 weeks then discontinued for equal periods of time to disallow the body to adapt to the effects of the drug. For fat-burning goals clenbuterol is often stacked with another fat-burning agent for quick effect, or alternated with another fat-burning agent by people who need to stay lean on a year-round basis. Usually cytomel (T3) is used for such purposes, with alternating cycles of 3 weeks each. If used together, cycles will not completely overlap, but differ slightly so as not to match the low doses with the low and the high doses with the high. A typical cycle for clenbuterol might be 3 weeks, with the daily amounts being 40/40/40/60/60/60/80/80/80/100/100/100/80/80/80/60/60/60/40/40/40 µg/day. Then stopping for three weeks and recommencing.
It's also commonly stacked with anabolic steroids . Usually non-aromatizing steroids that give the user a leaner and harder look, and allow for less water retention. They serve a main purpose of allowing the user to keep as much of his hard-earned muscle mass as he tries to shed the fat he has stocked up in the off-season with catabolic precursors such as clenbuterol. Clenbuterol is generally regarded as fairly safe6, hence its wide-spread use. It should be disadvised for all with blood pressure and/or previously diagnosed cardio-vascular problems. But most tolerate it quite well. By building up the dose over time they usually see when they've reached a dose that becomes too harsh. The use of clenbuterol will elicit higher body temperature, higher blood pressure and in some, especially at high doses, insomnia and jitters. Though these should not be nearly as pronounced with clenbuterol as they are with ephedrine and its legal counterpart ma huang. They are also easily remedied by shifting doses around so you don't take clenbuterol in the hours leading up to bedtime and most of it in pre-training phases when the drug can enhance your training vigor. Another good match for clenbuterol in a stack is the plant derivative yohimbine Hcl. It does concern the standardized product yohimbine here and not the raw material yohimbe, which is useless. In small doses of 20-30 mg per day, it can stop the down-regulation of the noradrenaline feedback mechanisms, that usually inhibit the actions of noradrenaline by reducing receptor affinity. This has two important uses. The first is that the length of action of clenbuterol can be enhanced by a few hours when using it together with yohimbine Hcl (although it already has a considerable half-life time7 of 36 hours and one daily dose should suffice) , and the second is that concomitant use of yohimbine Hcl may allow clenbuterol to induce its fatburning aspects on a longer term than the normal 2-3 weeks, so it can be used for 5-6 weeks instead. Yohimbine Hcl is, at least for now still, a legal supplement that can be acquired for very little money from legal sources and supplement companies.