People hear about a horse drug that causes rapid weight loss so they grab it, never knowing about its consequences.

The drug was first taken by some bodybuilders, because it makes you lose fat, but not muscle.

People said models and Hollywood types are now using the drug, which is meant only for horses.

"Everyone in Hollywood wants to be thin. It is a sign of achievement. And the tabloids keep constant track of who's the thinnest and what the weight watch is and if you gain a few pounds in Hollywood it's suddenly seen as a crisis," said Linda Wells, with Allure magazine.

One model, who did not want to be identified, took an illegal drug called clenbuterol years ago. We'll call her Jennifer.

Normally used to treat asthma in horses, clenbuterol has also been found to cause rapid weight loss.

"There are rumors that Hollywood celebrities are using this drug to become very thin, very quickly," Wells said.

"My body would look better than it already did, and what 20 year old wouldn't be like, alright! I want my body to look better than it does!" Jennifer said.

Despite being widely discussed and sold on the Internet, those pushing the drug rarely mention its potentially dangerous effects on the nervous system.

"Probably the prevalent thing was the rapid heartbeat -- just my heart was going to beat out of my skin" Jennifer said. "This wasn't a cup of coffee feeling. This was like three pots of coffee feeling."

"Just out of nowhere my eye would start going crazy twitching just from my nerves being so out of control," Jennifer said.

Fortunately for Jennifer, she stopped taking the drug before things got worse, and walked away with a valuable lesson.

"There's nothing at all that exists that is going to take the place of a consistent, good nutritional plan and working out, exercising on a regular basis. Nothing," Jennifer said.

"This is dangerous. This is really bad idea. You do not want to be taking this drug," Wells said.

On top of the fact that it's dangerous, some people said that after a few weeks of losing weight on the drug, it made them start gaining weight.