Clenbuterol is a sympathomimetic amine used by sufferers of breathing disorders as a decongestant and bronchodilator. Clenbuterol is a ß2 (Beta 2) agonist with stimulant and thermogenic effects. It causes an increase in aerobic capacity, central nervous system stimulation, and an increase in blood pressure and oxygen transportation. It increases the rate at which body fat is metabolized, simultaneously increasing the body's basal metabolic rate (BMR). In animal studies clenbuterol has shown anabolic activity, however this is unproven in humans and still undecided. Clenbuterol’s ability to stimulate fat cells and accelerate breakdown of triglycerides into free fatty acids is what makes it attractive to bodybuilders and people looking for fat reduction. Clenbuterol is a drug that might exhibit life threatening side-effects when abused, so care should be taken when using this drug. The dosage for the first couple of days should be very low and most find 30-40mcg tolerable as an initial dosage. When side-effects are bearable the dosage might be increased by 10-20mcg every three or four days. Increasing the dosage should be stopped when side-effects become too much to tolerate or when a maximum of 120mcg is reached per day. Never exceed 120mcg per day! (80mcg for women)

Clenbuterol will only work for a limited time before effects diminish. For most individuals this will take about 4 to 6 weeks due to the down-regulation of ß2 receptors. Since clenbuterol has thermogenic effects it is possible to determine whether it is still effective or not by taking ones body temperature. An elevated temperature of about 0.5 to 1C is a sign that the clenbuterol is still active. But the comparison should only be done under controlled and similar conditions – for example, early in the morning upon awakening. Having a reference temperature before any clenbuterol was taken will also help to make an accurate conclusion. In the past clenbuterol was cycled in on and off periods of about 2 weeks in an attempt to minimize receptor down-regulation. This is not necessary anymore, because drugs like ketotifen can now be taken in conjunction with clenbuterol. Ketotifen is an antihistamine used for asthma treatment in children. 

Ketotifen also up-regulates ß2 receptors making clenbuterol more effective and for longer periods. To have this up-regulatory effect it should be used at 3mg per day. A number of side-effects are likely to be experienced while taking clenbuterol and may include shaky hands, insomnia, sweating, increased blood pressure, and nausea. These side effects will generally subside after a week or so of use, once the user becomes accustomed to the drug. Clenbuterol hydrochloride is a central nervous system stimulant with potential for fatal overdose. Signs of overdose may include rapid breathing, blood pressure irregularities, irregular heartbeat, unconsciousness, trembling, shaking, panic, extreme restlessness, and severe nausea, vomiting or diarrhea.

Numerous bodybuilder deaths have been linked to the use of clenbuterol during the preceding weeks leading up to "sudden death syndrome". The cases where this has happened were mostly related to either doses of clenbuterol well above 120mcg per day, or dosages being increased too quickly. Clenbuterol is easily obtainable in South Africa, but the price varies greatly depending on the brand and administration route. Injectable versions are generally more expensive where oral versions are cheaper. The oral varieties can be found in powder (Ventipulmin), tablets, capsules.