TIH-METFORMIN

What it is

TIH-METFORMIN is metformin hydrochloride available in three strengths: 500 mg, 850 mg, and 1000 mg tablets. The 500 mg tablet is oblong and white, the 850 mg tablet is round and white, and the 1000 mg tablet is oval and white. The tablets are gluten free. Metformin is a biguanide with antihyperglycaemic effects on both basal and postprandial hyperglycaemia and does not stimulate insulin secretion and therefore does not cause hypoglycaemia.

Approved indications

— Type 2 diabetes mellitus not satisfactorily controlled by diet, where the risk of lactic acidosis is minimised by excluding predisposing factors, especially impaired renal, hepatic or cardiovascular function. — Use as initial therapy or in sulphonylurea failure, either alone or in combination with a sulphonylurea or as adjuvant therapy in insulin-dependent diabetes.

Dosing overview

The 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. Control may be attained within a few days but occasionally requires up to two weeks. In children from 10 years of age and adolescents, metformin can be used as monotherapy with a usual starting dose of one tablet of 500 mg or 850 mg once daily, given during meals or after meals. The maximum recommended dose in children is 2 g daily, taken as two or three divided doses.

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 that can occur due to metformin accumulation, and reported cases have occurred 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, and lactic acidosis is characterised by acidotic dyspnea, 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. 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 which may lead to worsening of the disease.

Contraindications

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

PBS listing

Information on PBS listing is not available in the provided source documents.

Regulatory history

TIH-METFORMIN was first registered on the Australian Register of Therapeutic Goods on 23 June 2020, with six variants registered across 500 mg, 850 mg, and 1000 mg strengths in both bottle and blister pack presentations.