Clenbuterol

As of fall, 2006, Clenbuterol is not an ingredient of any therapeutic drug approved by the U.S. Food and Drug Administration, but is still used as an unproven slimming aid, and is now banned for IOC-tested athletes.

Jason Grimsley, former Major League baseball pitcher, admitted to using this drug.

Former Major League Baseball first Baseman David Segui has admitted to ordering the substance.

Entertainer Britney Spears has been reported as being a user of the drug in order to boost rapid weight loss, according to reports from the newspaper, The Sun, and has been doing so for over half a year.

The tennis player Mariano Puerta was once penalized for use of clenbuterol.

Australian wrestler Mitchil Mann was also suspended for testing positive for the drug.

Clenbuterol is approved for use in some countries (via prescription only) as a bronchodilator for asthma patients. Recently though, the drug has been publicized for its off-label use as a weight loss drug.
It is commonly used as a slimming aid despite lack of sufficient clinical evidence supporting such use. With many major diet review websites talking about clenbuterol, and given its accessibility via the internet, the drug is widely used as a "dietary supplement". In fact, nowadays it is recommended by many physical trainers as the primary solution for those bodybuilders who desire to achieve sufficiently low body fat in order to look "cut".
In many cases, it is introduced into the training regime not as an illegal drug, but simply as a weight loss aid. This reduces some of the negative connotations attached to illicit drug use and thereby decreases any hesitation to take the drug on the part of the trainee