Metformin Viatris (Metformin Hydrochloride)

Metformin is an oral antidiabetic medication used in the management of type 2 diabetes mellitus.

• Type 2 diabetes mellitus: improves glycaemic control by lowering fasting plasma glucose and HbA1c.
• Prediabetes (impaired glucose tolerance): delays progression to overt diabetes when combined with lifestyle measures.
• Polycystic ovary syndrome (PCOS): reduces insulin resistance and may help restore regular menstrual cycles.

• Metformin primarily inhibits hepatic gluconeogenesis, reducing the amount of glucose released by the liver. It also enhances peripheral glucose uptake by increasing insulin‑stimulated translocation of GLUT4 transporters in muscle and adipose tissue, thereby improving overall insulin sensitivity without directly stimulating insulin secretion.

Metformin is generally well tolerated, but a range of adverse reactions can occur.

Common Side Effects

• Nausea: mild to moderate stomach upset, often transient.
• Diarrhoea: loose stools, usually early in therapy.
• Abdominal discomfort: cramping or bloating.
• Metallic taste: temporary alteration of taste perception.
• Loss of appetite: reduced desire to eat.
• Flatulence: increased intestinal gas.

Serious or Rare Side Effects

• Lactic acidosis: a rare but life‑threatening accumulation of lactate.
• Severe skin reactions: such as Stevens‑Johnson syndrome.
• Hepatic dysfunction: marked elevation of liver enzymes.
• Hypoglycaemia: when combined with insulin or secretagogues.
• Vitamin B12 deficiency: may develop with long‑term use.
• Pancreatitis: inflammation of the pancreas.

Metformin requires careful consideration of patient‑specific factors before and during therapy.

• Renal function: assess eGFR and avoid use in severe renal impairment.
• Lactic acidosis risk: contraindicated in conditions predisposing to hypoxia or severe hepatic disease.
• Alcohol consumption: limit intake to reduce acidosis risk.
• Iodinated contrast procedures: discontinue metformin temporarily and monitor renal function.
• Pregnancy and breastfeeding: evaluate benefits versus risks with a healthcare professional.
• Store at ambient temperature: keep in the original container, protect from moisture and heat.

Metformin may interact with several medicines, altering its efficacy or safety.

Major Interactions (Avoid)

• Iodinated contrast agents: can precipitate renal dysfunction and lactic acidosis.
• Cimetidine: may increase metformin plasma concentrations.
• Chronic alcohol abuse: heightens risk of lactic acidosis.

Moderate Interactions (Monitor Closely)

• Beta‑blockers: may mask symptoms of hypoglycaemia.
• Diuretics (especially thiazides): affect renal clearance of metformin.
• ACE inhibitors or ARBs: require monitoring of renal function and electrolytes.