What is clenbuterol?

In one line

Clenbuterol is an asthma-type drug made to open narrowed airways, which people misuse to lose fat or build muscle.

What is clenbuterol?
A name that comes up in diet-drug talk
Among people who want to lose fat fast, the drug name 'clenbuterol' comes up. But this drug was originally made to make breathing easier. What exactly is it, and what does it do in the body?
In short
An asthma-type drug that opens the airways
Clenbuterol is a drug that widens narrowed airways to make breathing easier. Some countries use it as an asthma medicine for people, but in the US it is not approved as a human drug. Using it without a prescription to lose fat or build muscle is drug misuse, which means using a drug the wrong way or too much.
Airways and asthma
When the airways narrow, breathing gets hard
When you breathe, air moves in and out of the lungs through tubes called bronchi, or airways. In asthma, these tubes swell and narrow, causing shortness of breath and wheezing. Drugs that relax the muscles around the airways and widen them are called bronchodilators, and clenbuterol is one of them.
What is adrenaline?
A hormone released under stress
A hormone is a substance made in one part of the body that travels in the blood and carries signals to other parts. Adrenaline is a hormone released in large amounts when you are scared or stressed, and it gets the body ready for sudden, hard effort. Stimulating the heart and widening the airways are also things adrenaline does.
What it does in the body
It switches on adrenaline's docking spot
Cells have spots where only certain substances fit and attach; these are called receptors. One of the receptors adrenaline attaches to is the beta-2 receptor, found in airway muscle, the muscles that move the body, the liver, blood vessels and more. Clenbuterol attaches to this receptor and switches on a signal similar to adrenaline's.
Whose medicine is it?
In the US, approved only for horses
In the US, clenbuterol is approved only as a syrup for horses whose airways get blocked. US law forbids using it in animals raised for meat. In Australia, too, it is not registered as a human medicine.
Farm animals and meat
Secretly treated meat caused mass poisonings
When drugs like clenbuterol are fed to farm animals, fat goes down and lean meat goes up. So clenbuterol was secretly fed to farm animals in the US, Europe, China and elsewhere. Mass poisonings, where many people at once had shaking hands, a pounding heart and headaches after eating liver or meat from such animals, were reported in Spain and elsewhere in Europe, and in China.
Why it comes up at the gym
Losing fat and building muscle
People who do bodybuilding or want to lose weight use clenbuterol without a prescription, hoping it will build muscle and cut fat. The World Anti-Doping Agency, which decides which drugs are banned in sport, puts clenbuterol in the same group as muscle-building drugs and bans it at all times, in and out of competition.
When poisoning happens
More than eight in ten were hospitalized
The most common signs of clenbuterol poisoning were a fast heartbeat, nausea and vomiting, and shaking hands. Among clenbuterol cases reported to one poisons information center in Australia, more than eight in ten people were admitted to hospital. One young man who used it for bodybuilding had his heart stop during sport and was brought back.
Heart damage
Even heart attacks in young users
When reports of clenbuterol side effects in people who exercise were gathered, heart problems were the most common. People had irregular heartbeats or heart attacks, where a blood vessel feeding the heart muscle gets blocked, and some died. Heart attacks were reported even in young bodybuilders with low risk of heart disease.
Common myth
Is it a harmless shortcut to weight loss?
No. Online, clenbuterol is sometimes presented as a harmless shortcut, but many countries have not approved it as a human medicine. In reports of side effects in people who exercise, heart problems were the most common harm, and some people died.
Summary
An airway drug misused for fat loss
Clenbuterol is an asthma-type drug made to open the airways, and it switches on the beta-2 receptor that adrenaline attaches to. It is not a harmless diet shortcut but a drug for which heart problems are the most reported harm. Related terms: adrenaline, beta-2 receptor, World Anti-Doping Agency prohibited list.