PHENTODUR

What it is

PHENTODUR contains phentermine as an ion-exchange resin complex, available in strengths of 15, 30 or 40 mg. It is supplied as modified release capsules. The ion-exchange resin is highly insoluble and releases phentermine at a rate dependent on cation concentration in gastrointestinal fluids, providing continuous and controlled ionic release over a 10 to 14 hour period.

Approved indications

— Management of obesity as a short-term adjunct in a medically monitored comprehensive regimen of weight reduction based on exercise, diet and behaviour modification in obese patients with a body mass index (BMI) of 30 kg/m² or greater. — Initiation of treatment in overweight patients with a lower BMI (25 to 29.9 kg/m²) which increases the risk of morbidity from a number of disorders.

Dosing overview

The recommended starting dose for adults and adolescents over 12 years is 30 mg daily as one capsule at breakfast, swallowed whole. Larger framed individuals may require 40 mg daily. The recommended maintenance dose, either continuous or intermittent, is 15 to 40 mg daily depending on responsiveness. Evening dosing should be avoided, as this agent may induce insomnia. Patients require medical review after a defined course of treatment, which should not exceed three months. PHENTODUR is not recommended for children under the age of 12 years as safety and efficacy have not been established. PHENTODUR is not recommended for the elderly.

Key safety warnings

Serious regurgitate cardiac valvular disease, primarily affecting the mitral, aortic and/or tricuspid valves, has been reported in otherwise healthy persons who had taken a combination of fenfluramine or dexfenfluramine with phentermine for weight loss. There have been no reported cases to date of valvular heart disease occurring with the use of phentermine alone. Since selective serotonin reuptake inhibitors, ergot-like drugs and clomipramine affect serotonin disposition, there remains a theoretical risk that combination of these agents with phentermine may be associated with cardiac valvular disease and is not recommended. Cases of severe, sometimes fatal primary pulmonary hypertension have been reported in patients who have received anorectics, with duration of treatment beyond three months significantly increasing the risk. The possibility of an association between primary pulmonary hypertension and the use of phentermine alone cannot be ruled out, with very rare cases reported in patients who have taken phentermine alone. The initial symptom of primary pulmonary hypertension is usually dyspnoea, with other early symptoms including angina pectoris, syncope, lower extremity oedema or unexplained onset of diminished exercise tolerance; treatment should be immediately discontinued and the patient referred to a specialist unit for investigation. Cardiovascular and cerebrovascular events have rarely been reported, mainly in association with rapid weight loss, and weight loss should be gradual and controlled in obese patients undergoing treatment with PHENTODUR. Alcohol may increase CNS side effects such as dizziness, lightheadedness and confusion, and its concurrent use should be avoided with PHENTODUR.

Contraindications

PHENTODUR is contraindicated in pulmonary artery hypertension; existing heart valve abnormalities or heart murmurs; moderate to severe arterial hypertension; cerebrovascular disease; severe cardiac disease including arrhythmias and advanced arteriosclerosis; known hypersensitivity to sympathomimetic drugs; hyperthyroidism; agitated states or a history of psychiatric illnesses including anorexia nervosa and depression; glaucoma; history of drug or alcohol abuse or dependence; and concomitant treatment with Monoamine Oxidase Inhibitors or within 14 days following their administration.

Regulatory history

PHENTODUR was first registered on the Australian Register of Therapeutic Goods on 11 August 2021, with three registered variants comprising 15 mg, 30 mg and 40 mg modified release capsules.