Metformin

Key points

• Metformin belongs to the biguanide class of antidiabetic medicines.
• It is supplied as film-coated and prolonged-release tablets.
• Lactic acidosis is a serious side effect that requires immediate medical attention.

What metformin is used for

Metformin is an adjunct to diet and exercise for improving blood sugar control in type 2 diabetes mellitus. It helps keep blood glucose within the target range. General information on treatment is available under diabetes management.

How it works

The medicine reduces glucose production in the liver and decreases glucose absorption in the intestine. It also improves the body’s sensitivity to insulin. Effects usually begin within 2–3 hours and last around 6–12 hours.

Metformin products on MayChemist

Glucophage tablets contain metformin in 500 mg, 850 mg and 1000 mg strengths, for type 2 diabetes mellitus. The metformin ingredient page has more on the medicine. Pharmacy partners in India ship orders to Malaysia in discreet packaging.

Safety

Metformin is contraindicated in severe renal impairment, diabetic ketoacidosis and hypersensitivity to the medicine. The label specifies an eGFR below 30 mL/minute/1.73 m², since the kidneys are the main route of clearance.

Kidney function should be monitored during treatment, and the medicine is withdrawn before contrast imaging. There is a risk of vitamin B12 deficiency.

Nausea, vomiting and diarrhoea are common; abdominal pain and loss of appetite can also occur. Lactic acidosis is serious and needs immediate medical attention. Its onset can be subtle, with malaise, muscle aches, breathing difficulty, drowsiness and abdominal pain. Risk factors include kidney impairment, age 65 or older, contrast studies, surgery, low-oxygen states such as acute heart failure, heavy alcohol use, liver impairment, mitochondrial disease and interacting drugs such as topiramate. If lactic acidosis is suspected, metformin should be stopped and hospital care sought, where prompt haemodialysis is recommended.

Alcohol and iodinated contrast agents interact with metformin. Insulin is usually preferred during pregnancy; small amounts may pass into breast milk, so consult a physician. For use in children, consult a specialist.

What the sources say

• Metformin tablets are indicated, with diet and exercise, for adults and children aged 10 and older with type 2 diabetes (DailyMed).
• Metformin is described as a biguanide; it lowers glucose absorbed from food and made by the liver, and increases the body’s response to insulin (MedlinePlus).
• Reported postmarketing cases of metformin-associated lactic acidosis have involved death, hypothermia, hypotension and resistant bradyarrhythmias (DailyMed).

Further reading

• Metformin
• Metformin - healthdirect
• Meet Metformin - Diabetes Australia
• Glucophage 500 mg film coated tablets - Patient Information