Phentremine is supposed to be a replacement for Ephedra, now that Ephedra has been taken off the market.  Phentremine is advertised as an appetite suppressant that helps a person lose about five pounds a week, if not more weight.  On the website it claims that this product increases your metabolism, and energy as it helps you lose weight.   The ingredients are listed as Hoodia Gordonii, Citrus Aurantium and Evodamine.  The text on this site keeps stressing that these are all natural ingredients, but I have not heard of them.  Apparently Phentremine comes in two formulas, and the strongest is Phentremine X which has an extra bit of Willow Bark in it.  Supposedly these ingredients work to turn off the brain stimulants that make you hungry.  You might want to check with your doctor or at least a nutritionist before taking anything that speeds up your metabolism and effects your brain.