Learn about the side effects of phentermine, from common to rare, for consumers and healthcare professionals. Overview: Phentermine is used short-term to help with weight loss in people who have obesity or are overweight. Common side effects include fast heartbeat, high blood pressure, and restlessness. Learn about phentermine (Adipex-P) usage and dosing. Read the latest news and reviews about the drug as well as potential side effects and popular alternatives. Phentermine, sold under the brand name Adipex-P among others, is a medication used together with diet and exercise to treat obesity. [3] It is available by itself or as the combination phentermine/topiramate. [8] Alongside a healthy diet and exercise, the drug phentermine may help you lose weight. This article explains its benefits, dosage, and possible side effects. Phentermine is used for a limited period of time to speed weight loss in overweight people who are exercising and eating a low-calorie diet. Phentermine is in a class of medications called anorectics. Phentermine (Adipex-P, Lomaira) is a prescription medicine used to lessen appetite. It can help weight loss by making you less hungry. Or it can help you feel full longer. Phentermine also is offered combined with topiramate for weight loss (Qsymia). The combined drug is approved for long-term use. Phentermine is approved for use for up to 12. Phentermine is an appetite suppressant used together with diet and exercise to treat obesity. Learn about side effects, interactions and indications. Description Phentermine is used for weight reduction in patients with obesity. It is used in patients with obesity who have not been able to lose weight with diet and exercise alone. This medicine works by suppressing your appetite. This medicine is available only with your doctor's prescription. Phentermine (Adipex-P, Lomaira) is an oral weight-loss medication that works by reducing appetite. In studies, more than 80% or more of people lost at least 5% of their body weight while taking phentermine.