The Truth About Clenbuterol (2024)

Clenbuterol is a beta agonist. In some parts of the world, it is used to treat breathing difficulties caused by conditions such as asthma or chronic obstructive pulmonary disease (COPD). In the United States, however, clenbuterol is not approved for this purpose. What's more, it has been used illegally by athletes as a performance enhancer similar to anabolic steroids.

What It Does

Beta agonists copy the effect of hormones called catecholamines—specifically epinephrine but also norepinephrine and dopamine. They act on the smooth muscle of the bronchi and bronchioles (the airways in the lungs), uterus, and the intestines as well as some blood vessels in the body by targeting beta adrenergic receptors in these locations.

Beta agonists prevent smooth muscles from contracting. They sometimes are used as tocolytics, medications that can delay labor by relaxing the smooth muscle of the uterus.

Bronchodilation

Beta agonists including clenbuterol are strong bronchodilators, drugs that can increase the diameter of the airways. They accomplish this by relaxing the smooth muscle tissue of the breathing tubes.

Since they open the airways, beta agonists can effectively treat asthma, COPD, and other conditions in which breathing is difficult because inflammation and/or mucus blocks the bronchioles and prevents airflow.

Bronchodilation is far from the only effect that beta agonists have on the body, however, and multiple beta agonists exist each one having a slightly different profile including toxicity level, duration of effects, and potential for harmful side effects.

Clenbuterol is similar in profile to another beta agonist called albuterol. Clenbuterol is a long-acting beta agonist. Clenbuterol is not typically used because there are similar drugs available that have the same desired effects on the breathing passageways but are less likely to cause dangerous side effects.

Anabolic Effects

Most of the studies showing anabolic effects of clenbuterol have been done on animals, but, at least one small study done on humans with chronic heart failure did show an increase in lean mass and decrease in body fat. However, this same study also showed that endurance (the length of time these individuals were able to exercise) actually decreased.

Studies on rats have shown similar effects on lean muscle mass and decreased body fat. It is also interesting to note that a study on rats showed that albuterol has similar anabolic effects at safer doses.

Clenbuterol Side Effects Long Term

These studies are the basis of the abuse of clenbuterol in athletes. However, significant large-scale studies on humans on clenbuterol have not been conducted, and long-term effects on humans using clenbuterol for this purpose have not been done.

How Is Clenbuterol Used

When used for breathing difficulties, beta agonists are usually inhaled. Using a metered-dose inhaler may help to mitigate the side effects of the medication. However, other forms of this medication exist, including oral pills, syrups, and injectable forms.

Clenbuterol is a long-acting beta agonist, so in countries where it is used for the treatment of asthma, it should be used in conjunction with a short-acting beta agonist or rescue medication (inhaled corticosteroid) rather than used alone.

When used for its anabolic properties this medication is often taken in very large doses either orally or injected, which increases the likelihood of experiencing dangerous side effects.

Dangers and Abuse

Clenbuterol is not approved in many countries due to its potential to become toxic at even very low doses. Harmful side effects may include tachycardia, heart palpitations, tremors, seizures, increased blood sugar, cardiac arrest, and even death. These dangerous side effects are more likely to occur when the drug is used at high doses.

In the United States clenbuterol is sold on the black market, sometimes under the street name "clen." it is often purchased by bodybuilders or athletes for its alleged abilities to decrease body fat and increase muscle mass.

Female athletes seem to be more likely to abuse the drug than male athletes because clenbuterol side effects for female aren't the typical issues associated with anabolic steroids such as facial hair, deepening of the voice, and thickening of the skin.

It has also been mixed with heroin, possibly for its stimulant properties, and there have been cases of hospitalization and even death after individuals have used heroin laced with clenbuterol.

Potential treatments may include intravenous fluids or medications called beta blockers to lower the heart rate. Sedatives are sometimes given to mitigate the stimulant properties of clenbuterol.

Veterinary Use

There is only one medication containing clenbuterol that is approved for use in the United States. Ventipulmin is a syrup containing a small amount of clenbuterol that is approved by the Food and Drug Administration for use in horses to treat respiratory obstruction.

In the past, clenbuterol has been used in livestock as a means to increase lean muscle mass. Currently, clenbuterol is prohibited in the United States for use in any livestock used for food because the drug will be present in the meat after the animal is slaughtered. Consuming this meat may be dangerous.

Some athletes have claimed to have ingested contaminated meat when they have tested positive for clenbuterol prior to athletic events. In some countries, clenbuterol is used in pregnant cattle to prevent early labor.