Phentermine
Weight Management
In plain English
Phentermine is an FDA-approved appetite suppressant that has been used for short-term weight loss since the 1950s. It is a stimulant related to amphetamine and works by reducing hunger. It is intended for short-term use alongside diet and exercise, and it is not appropriate for people with certain heart conditions or uncontrolled high blood pressure. Common effects include a faster heart rate, higher blood pressure, restlessness, dry mouth, and trouble sleeping.
The science
Phentermine is a sympathomimetic amine that promotes release of norepinephrine (and to a lesser degree dopamine and serotonin) in the hypothalamus, suppressing appetite. It is FDA-approved for short-term (typically up to 12 weeks) management of obesity. The strongest modern controlled evidence comes from the fixed-dose combination with topiramate: in the 56-week CONQUER phase 3 trial (n=2,487), phentermine 15 mg/topiramate 92 mg produced ~9.8% weight loss versus 1.2% for placebo. Phentermine alone raises heart rate and blood pressure, can cause insomnia and irritability, and carries abuse potential as a controlled substance; it is contraindicated in cardiovascular disease, hyperthyroidism, and with MAO inhibitors.