Phentermine comes as tablets and extended-release capsules. It usually is taken as a single daily dose in the morning or three times a day 30 minutes before meals. Phentermine is taken once daily, in the morning, by mouth in the form of a tablet pill. Phentermine is only available by prescription. Weight Loss MD only uses pharmaceutical grade medication from manufactures in the United States. Phentermine is the most widely-prescribed weight-loss medication in the United States. It first received FDA approval in 1959 as an appetite suppressant for the short-term management of obesity. Phentermine (contracted from phenyl-tertiary-butyl amine), also known as α,α-dimethylphenethylamine, is a psychostimulant drug of the substituted amphetamine chemical class, with pharmacology similar to amphetamine. User Reviews for Phentermine. Also known as: Adipex-P, Lomaira, Suprenza. The following information is NOT intended to endorse drugs or recommend therapy. What other drugs will affect phentermine? Taking phentermine together with other diet medications such as fenfluramine (Phen-Fen) or dexfenfluramine (Redux) can cause a rare fatal lung disorder called pulmonary hypertension. Phentermine is not appropriate or safe for everyone. It is critical that you inform your doctor of all current and past medical conditions, as well as any current or recent medications and supplements you may be taking. Phentermine is a pharmaceutical diet pill which requires a prescription to be purchased online. It contains one active ingredient ( phentermine hydrochloride ) and comes in 37.5 mg, 30 mg and 15 mg strengths. Phentermine is the generic form of the brand-name drugs Adipex-P, Suprenza, and Ionamin, which are used for weight loss. Phentermine decreases appetite and stimulates the body to burn calories. Phentermine is a prescription weight-loss drug. Most doctors agree that phentermine works by suppressing the appetite and upregulating the metabolism, though the specific pathways are not fully understood.