Short answer: Phendimetrazine has a half-life of about 3.7 hours. People vary, so treat these as estimates.
Phendimetrazine is a stimulant appetite suppressant related to amphetamine, used for a few weeks alongside a calorie-restricted diet. It has been sold as Bontril; this page uses a current label for generic 35 mg tablets.
Also known as: Bontril, phendimetrazine tartrate.
The label read here is for phendimetrazine tartrate 35 mg immediate-release tablets.
The label approves phendimetrazine as a short-term (a few weeks) add-on to a calorie-restricted weight-loss plan for obesity in people with a starting BMI of 30 or more who have not responded to diet and exercise alone, used on its own and not with other weight-loss drugs. Label dosing: one 35 mg tablet two or three times a day, one hour before meals, at the lowest dose that works (half a tablet, 17.5 mg, may be enough for some), and not more than 2 tablets three times a day. The label calls it a Schedule III controlled substance. Tolerance develops within a few weeks; when it does, the drug is stopped rather than the dose raised. It gives no missed-dose instruction.
The label has no boxed warning. It is not used with an allergy to stimulant amines, advanced hardening of the arteries, heart disease with symptoms, moderate or severe high blood pressure, an overactive thyroid or glaucoma, in highly nervous or agitated people, with a history of drug abuse, or with other stimulants including MAO inhibitors. Rare, often fatal pulmonary hypertension and heart valve disease have been reported with appetite suppressants, including with fenfluramine or dexfenfluramine; the label notes no valve cases with phendimetrazine used alone. Side effects, listed without percentages, include palpitations, fast heartbeat, raised blood pressure, restlessness, insomnia, dry mouth and constipation. See phendimetrazine side effects, phendimetrazine dosing schedule and phendimetrazine vs phentermine.
The phendimetrazine label gives an average elimination half-life of about 3.7 hours, for both the immediate-release and extended-release forms, and says the 35 mg tablet is absorbed much faster than the extended-release form. It leaves mainly through the kidneys. The label gives no time to peak.
Numbers shown are taken from the source above. Half-life varies from person to person.
How Dose Track handles peptides · Reconstitution calculator · Half-life calculator