I've been researching the same thing for days. Phentermine has to be prescribed by a Dr. They say they sale it on line but it's an herbal version, not actually the same thing. I've also been researching Adapexin. It's the top diet pill pick of 2011 that doesn't need a Rx. Also 2010 I think. There's another Adipixen I believe that also needs a Rx. Good luck.
There are a number of weight loss pills that are available at drugstore, health food stores or supermarkets but they have not been proved effective and some may be dangerous. It would be better if you use natural ways to lose weight like doing exercise and dieting. If you should use the weight loss pills then I would recommend you to talk to your doctor first before using, for more information, visit http://www.mayoclinic.com/health/weight-loss/HQ01160.