Phentermine (phentermine hydrochloride) is a generic drug used to treat obesity. Learn about side effects, drug interactions, dosages, warnings, and more. 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. [9] Alongside a healthy diet and exercise, the drug phentermine may help you lose weight. This article explains its benefits, dosage, and possible side effects. Detailed Phentermine dosage information for adults. Includes dosages for Obesity; plus renal, liver and dialysis adjustments. 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. 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. 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 and Lomaira) is a schedule IV controlled prescription drug used as a short-term weight loss in conjunction with diet and other lifestyle modifications to treat obesity. 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.