Okay... this is more a warning post than a, "Does it work?" post, but if you have ever used it, feel free to share...
Clenbuterol is a drug FDA approved to be used on horses with obstructed airways. However, someone (in Hollywood, no less) got the idea to use it for weight loss. I suppose the premise is that you can drop 14 pounds or so in two weeks taking this drug while preserving your muscle (or actually bulking it further). It heats the body up and increases your heart rate, thus burning more calories (or so it is explained). I guess actors, actresses and models are going nuts over this stuff. The only way to buy it is through pharmacies in Mexico or Canada, or actually going to one of those countries and purchasing it. Now, remember you would get the dosage that the horse with the obstructed airways would have.
Small dangers of this drug:
Shaky hands, dizziness, jitters, elevated blood pressure and headaches
Abnormal heart rhythms, stroke, death
Here is an article on it. Read the comments, it's crazy how many people want this stuff!
Some people claim they lost 40 pounds in a month, while some say to only use it if you work out... or even for a quick fix, like the weeks coming up to a wedding.
So yeah, anyways... watch out. It may work, but it'll cost you.