Clenbuterol

Clenbuterol is a decongestant and bronchodilator used in a variety of respiratory diseases. It belongs to the group of beta-sympathomimetics.

Uses and indications

Clenbuterol is a long-acting antiasthmatic and broncholytic agent. It is used for long-term therapy of bronchial asthma, COPD and chronic obstructive bronchitis. It is not suitable for acute treatment of bronchospasm due to its delayed onset of action.

Unlike other representatives of this group, it is not administered by inhalation, but as a tablet or oral solution. It is often combined together with ambroxol, an expectorant.

Clenbuterol is approved in Germany and Austria, but not in the United States. It is also used in many countries for veterinary use.

History

Clenbuterol was developed and first approved in the 1960s. In the years that followed, clenbuterol fell into disrepute due to its use as a doping agent. In the early 2000s, it was also touted as a "weight-loss" product. However, this effect has proven to be groundless.

Pharmacodynamics and mechanism of action

Clenbuterol is a β2-sympathomimetic and which binds to β2-receptors. This is due to its structural similarity to epinephrine and norepinephrine, the natural agonists of this receptor. Activation of β2-receptors by clenbuterol leads to smooth muscle relaxation in the lungs, gastrointestinal tract, uterus, and various blood vessels. Activation of β2-receptors also cause vasodilation of the heart muscle.

In asthma and similar pulmonary conditions, bronchial smooth muscle spasms, making breathing difficult. The administration of clenbuterol can minimize the occurrence of bronchospasm. Because of its prolonged action, and slow onset of action, it is not suitable for the treatment of acute bronchospasm.

Pharmacokinetics

Absorption after oral administration is rapid and almost complete (98%). The half-life is about 36-39 hours.

Drug interactions

Interactions may occur with the following drugs:

• When used with other β2-sympathomimetics, anticholinergics, tricyclic and MAO inhibitors, and narcotic gases, side effects on the cardiovascular system may be increased.
• Theophylline, corticosteroids, digitalis preparations, and diuretics (except potassium-sparing diuretics) may reduce the risk of potassium deficiency
• Beta-blockers may reverse the effect of clenbuterol
• The blood sugar-lowering effect of antidiabetic agents may be reduced with concomitant treatment
• When clenbuterol and antitussives are taken at the same time, a dangerous buildup of secretions may occur due to the impaired cough reflex

Contraindications

Clenbuterol should not be used in the following cases:

• In case of allergy to clenbuterol
• In hyperthyroidism
• hypertrophic obstructive cardiomyopathy
• In tachycardic arrhythmias (too fast heartbeat)
• pheochromocytoma (a tumor of the adrenal glands)

Side effects

The following side effects may occur.

Common:

• Palpitations
• Accelerated heartbeat
• muscle tremor
• Nervousness

Occasional:

• Headache
• Vomiting
• Nausea
• Dry mouth
• Indigestion and diarrhea
• skin rash
• muscle pain
• Muscle cramps

Not known:

• Cardiac arrhythmias
• Angina pectoris (tightness of the heart)
• Dizziness
• Drop in blood potassium levels
• Hypersensitivity reactions
• Restlessness

Pregnancy and breastfeeding

Clenbuterol is not recommended during pregnancy. This is especially true for the first 3 months of pregnancy and for the days before delivery due to its labor-inhibiting effects.

Clenbuterol passes into breast milk. Therefore, it should not be used during breastfeeding or breastfeeding should be interrupted.

Misuse

Clenbuterol can increase cardiac output, maximum heart rate, and thus exercise performance in athletes in the short term. It also increases basal metabolic rate and an anabolic effect on muscle growth is discussed. Because of these effects, it can be misused by competitive athletes for doping purposes. Therefore, it is a banned substance by the International Olympic Committee (IOC).

In the recent past, it has also been touted as a so-called "weight loss product". However, there are too few clinical studies available for this use.