METFORMIN-WGR

What it is

Metformin-WGR contains metformin hydrochloride and is available in 500 mg, 850 mg, and 1000 mg tablet strengths. Metformin is a biguanide with antihyperglycaemic effects, lowering both basal and postprandial plasma glucose, and does not stimulate insulin secretion and therefore does not cause hypoglycaemia.

Approved indications

— Type 2 diabetes mellitus in adults, children from 10 years of age and adolescents, particularly in overweight patients, when dietary management and exercise alone does not result in adequate glycaemic control. — In adult patients, metformin may be used as initial treatment or in sulfonylurea failures either alone or in combination with a sulfonylurea and other oral agents or as adjuvant therapy in insulin requiring type 2 diabetes.

Dosing overview

Tablets should be taken in divided doses with meals, initially 500 mg once or twice a day and if necessary increased over a few weeks up to 1 g three times per day. 500 mg three times a day is often sufficient to obtain diabetic control, and if necessary, the dose can be increased to 1 g three times daily, which is the maximum recommended daily dose. In children from 10 years of age and adolescents, the usual starting dose is one tablet of 500 mg or 850 mg once daily given during or after meals, with a maximum recommended dose of 2 g daily. In elderly patients, the initial and maintenance dosing should be conservative due to the potential for decreased renal function, with any dosage adjustment based on careful assessment of renal function, and elderly patients should not be titrated to the maximum dose.

Key safety warnings

Life threatening lactic acidosis can occur due to accumulation of metformin, with risk factors including renal impairment, old age and the use of high doses of metformin above 2 g per day. Lactic acidosis is a rare but serious metabolic complication with high mortality in the absence of prompt treatment, and reported cases have occurred primarily in diabetic patients with significant renal failure. The risk must be considered in the event of non-specific signs such as muscle cramps with digestive disorders and severe weakness, and lactic acidosis is characterised by acidotic dyspnoea, abdominal pain and hypothermia followed by coma. Metformin induces a reduction in thyrotropin levels in patients with treated or untreated hypothyroidism, and regular monitoring of TSH levels is recommended in patients with hypothyroidism. 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 in patients with risk factors known to cause vitamin B12 deficiency. In patients with known mitochondrial diseases such as Mitochondrial Encephalopathy with Lactic Acidosis and Stroke-like episodes syndrome and Maternal inherited diabetes and deafness, metformin is not recommended due to the risk of lactic acidosis exacerbation and neurologic complications.

Contraindications

Metformin-WGR is contraindicated in juvenile diabetes mellitus that is uncomplicated and well regulated on insulin, diabetes mellitus regulated by diet alone, during or immediately following surgery where insulin is essential, any type of metabolic acidosis such as lactic acidosis or diabetic ketoacidosis, hypersensitivity to metformin hydrochloride or to any of the excipients, and diabetic pre-coma. Renal failure or renal dysfunction with creatinine clearance less than 60 mL/min is contraindicated, as are acute conditions with the potential to alter renal function such as dehydration, severe infection and shock. Intravascular administration of iodinated contrast materials is contraindicated, as are acute or chronic diseases which may cause tissue hypoxia such as cardiac failure, recent myocardial infarction, respiratory failure, pulmonary embolism, shock, acute significant blood loss, sepsis and gangrene. Pancreatitis, elective major surgery, severe hepatic insufficiency, acute alcohol intoxication, alcoholism and lactation are also contraindicated.

PBS listing

No information regarding PBS listing is available in the provided documents.

Regulatory history

Metformin-WGR was first approved on 29 March 2019. ARTG registration includes metformin hydrochloride 500 mg, 850 mg and 1000 mg tablet formulations first listed on 29 March 2019, and extended-release formulations of 500 mg and 1000 mg first listed on 5 September 2016.