APO-METFORMIN

What it is

APO-METFORMIN XR is available as modified release tablets containing either 500 mg or 1000 mg of metformin hydrochloride. Metformin is an oral anti-diabetic agent and biguanide with antihyperglycaemic effects, lowering both basal and postprandial plasma glucose. It does not stimulate insulin secretion and therefore does not produce hypoglycaemia.

Approved indications

— Treatment of type 2 diabetes mellitus in adults, particularly in overweight patients, when dietary management and exercise alone does not result in adequate glycaemic control.

Dosing overview

For patients new to metformin, the usual starting dose is one APO-METFORMIN XR 500 tablet, once daily, with the evening meal. After 10 to 15 days the dose should be adjusted on the basis of blood glucose measurements, with dosage increases made in increments of 500 mg every 10 to 15 days, up to a maximum of 2000 mg once daily with the evening meal. APO-METFORMIN XR 1000 is intended as maintenance therapy for patients currently treated with either 1000 mg or 2000 mg metformin hydrochloride. Metformin may be used as monotherapy or in combination with other oral hypoglycaemic agents, or with insulin.

Key safety warnings

Life-threatening lactic acidosis can occur due to accumulation of metformin; the main risk factor is renal impairment, with other risk factors including old age associated with reduced renal function and high doses of metformin hydrochloride (≥ 2 g per day). Lactic acidosis is a rare but serious metabolic complication that can occur due to metformin accumulation, with reported cases occurring primarily in diabetic patients with significant renal failure. The risk of lactic acidosis must be considered in the event of non-specific signs such as muscle cramps with digestive disorders; lactic acidosis is characterised by acidotic dyspnea, abdominal pain and hypothermia followed by coma. Metformin induces a reduction in thyrotropin (thyroid stimulating hormone) levels in patients with treated or untreated hypothyroidism, and regular monitoring of TSH levels is recommended in patients with hypothyroidism. In patients with known mitochondrial diseases such as Mitochondrial Encephalopathy with Lactic Acidosis and Stroke-like episodes (MELAS) syndrome and Maternal inherited diabetes and deafness (MIDD), metformin is not recommended due to the risk of lactic acidosis exacerbation and neurologic complications. It is recommended that vitamin B12 serum levels are monitored annually, as the risk of low vitamin B12 levels increases with increasing metformin dose, treatment duration, and/or in patients with risk factors known to cause vitamin B12 deficiency.

Contraindications

APO-METFORMIN XR is contraindicated in patients with hypersensitivity to metformin or to any excipients, any type of metabolic acidosis (such as lactic acidosis or diabetic ketoacidosis), diabetic pre-coma, renal failure or renal dysfunction (creatinine clearance <60 mL/min), acute conditions with the potential to alter renal function (dehydration, severe infection, shock), intravascular administration of iodinated contrast agents, acute or chronic disease which may cause tissue hypoxia (cardiac failure, recent myocardial infarction, respiratory failure, pulmonary embolism, shock, acute significant blood loss, sepsis, gangrene, pancreatitis), major surgery, severe hepatic insufficiency, acute alcohol intoxication, alcoholism, and lactation.

PBS listing

APO-METFORMIN XR 500 mg tablet (extended release) is listed on the PBS with 2 items under a restricted scheme, with an ex-manufacturer price of A$4.00.

Regulatory history

APO-METFORMIN XR 500 mg and APO-METFORMIN XR 1000 mg modified release tablets were first registered on the ARTG on 2017-01-04 as blister pack formulations. Bottle pack formulations of both strengths were subsequently registered on 2025-06-26.