Products
Clenbuterol is not commercially available as a human drug in many countries, but exclusively as a veterinary drug for the treatment of respiratory diseases (e.g., Ventipulmin ad us vet). It is available only on medical prescription. In other countries, clenbuterol is on the market in tablet and drop form (Spiropent).
Structure and properties
Clenbuterol (C
12
H
18
Cl
2
N
2
O, M
r
= 277.2 g/mol) is a phenylethylamine derivative and a racemate. It has a similar structure to other beta2-sympathomimetics, for example, salbutamol (Ventolin, generics). In medicinal products, it is present as clenbuterol hydrochloride, a white crystalline powder that is soluble in water.
Effects
Clenbuterol (ATC R03AC14) has sympathomimetic, bronchodilator, and anti-inflammatory properties. It is anabolic (growth-promoting), promotes insulin release, builds muscle, and breaks down fat. It stimulates, in deep doses, the adrenergic β
2
-receptors of bronchial muscles. At high doses, it is less selective. When taken orally, effects occur within approximately 5-20 minutes and last for up to 14 hours. The terminal half-life is reported to be 34 hours.
Indications
For the treatment of obstructive airway diseases, e.g., asthma and chronic obstructive bronchitis. Clenbuterol is approved for this purpose as a veterinary drug in many countries. There are none commercially available for human use.
Abuse as a doping agent
Because of its anabolic effects, clenbuterol can be abused as a doping agent and anabolic steroid in competitive sports and bodybuilding. It is on the doping list and is prohibited before, during and after competition. For example, professional cyclist Alberto Contador was convicted of clenbuterol abuse by the International Court of Justice for Sport in 2012 and was forced to forfeit his victory in the 2010 Tour de France. Clenbuterol is used in animal fattening as an illegal growth-promoting agent because it promotes the building of muscle meat while also breaking down fat. Consumption of contaminated meat can lead to false positive doping results, as was probably the case with table tennis pro Dimitrij Ovtcharov. Whether clenbuterol is actually suitable as a doping agent in humans is not undisputed. In any case, its misuse should be discouraged.
Dosage
According to the drug label. Clenbuterol may be taken as a solution by inhalation or orally.
Contraindications
- Hypersensitivity
- Severe hyperthyroidism
- Certain cardiac arrhythmias
- Hypertrophic obstructive cardiomyopathy
For complete precautions, see the drug label.
Interactions
There are numerous drug-drug interactions possible. They can be found in the drug label. Clenbuterol is excreted largely unchanged in the urine.
Adverse effects
As with other beta2-sympathomimetics, the most common adverse effects include tremor (shaking), headache, restlessness, nausea, heartburn, dizziness, muscle pain, muscle cramps, nervousness, allergic reactions, and urinary retention. Cardiovascular disorders such as rapid pulse, arrhythmias, chest pain, extrasystoles, and ischemia are possible. Hypokalemia, hyperglycemia, insulin elevation, and renal disorders are rare. Such side effects are also possible when meat contaminated with clenbuterol is consumed. Dangerous overdoses with rapid heartbeat, cardiac arrhythmias, low blood pressure, shock and convulsions may also occur.
