“….Phentermine is a ß-phenethylamine derivative that stimulates the release of norepinephrine and dopamine from nerve terminals. Although phentermine is not approved by the FDA for long-term use, it is the most commonly prescribed anorexiant medication in the United States [1], presumably because it is less expensive than sibutramine. Phentermine was approved by the FDA more than 30 years ago, when the criteria needed for approval were less rigorous than they are today. Therefore, fewer studies have evaluated the efficacy and safety of phentermine therapy than have evaluated sibutramine and orlistat. Only one long-term (36 weeks) RCT evaluated the effect of phentermine therapy on body weight [2]. In that study, obese women were randomized to diet therapy and either treatment with daily phentermine, daily phentermine every other month alternating with daily placebo every other month, or daily placebo. Approximately two-thirds of the 108 enrolled subjects completed the study; among completers, the groups receiving either continuous or intermittent phentermine therapy lost about 13% of their initial weight, compared with a 5% weight loss in the placebo group. The most common side effects of phentermine are dry mouth, insomnia, and constipation. Although all sympathomimetic agents can increase blood pressure and heart rate, these side effects are uncommon when there is adequate weight loss…..”