METERMINE

What it is

Metermine is a phentermine capsule available in three strengths (15 mg, 30 mg, and 40 mg), where phentermine is formulated as an ion-exchange resin complex. The formulation provides continuous and controlled ionic release over a 10 to 14 hour period. Phentermine is a sympathomimetic amine with significant anorectic activity, with its appetite suppressant effect generally considered to be exerted through the hypothalamus.

Approved indications

— Management of obesity as a short-term adjunct in a medically monitored comprehensive regimen of weight reduction based on exercise, diet (caloric/kilojoule restriction) and behaviour modification in obese patients with a body mass index (BMI) of 30 kg/m² or greater. — Treatment can be initiated 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

Adults and adolescents over 12 years take one capsule daily at breakfast, swallowed whole. The recommended starting dose is 30 mg daily. 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. Patients require medical review after a defined course of treatment, which should not exceed three months.

Key safety warnings

Serious regurgitative 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. Cases of severe, sometimes fatal primary pulmonary hypertension have been reported in patients who have received anorectics, and the possibility of an association between primary pulmonary hypertension and the use of phentermine alone cannot be ruled out, though there have been very rare cases of primary pulmonary hypertension in patients who reportedly 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 the unexplained onset or aggravation of diminished exercise tolerance, and treatment should be immediately discontinued and the patient referred to a specialist unit for investigation under these circumstances. 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 Metermine. 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.

Contraindications

Metermine is contraindicated in patients with pulmonary artery hypertension; existing heart valve abnormalities or heart murmurs; moderate to severe arterial hypertension; cerebro-vascular disease; severe cardiac disease including arrhythmias or 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/alcohol abuse or dependence; or concomitant treatment with Monoamine Oxidase (MAO) Inhibitors or within 14 days following their administration.

Regulatory history

Metermine phentermine capsules in three strengths (15 mg, 30 mg, and 40 mg) were first listed on the Australian Register of Therapeutic Goods on 1 July 2004.