Management overview for metformin poisoning

Metformin is an antidiabetic drug that is available as immediate-release or modified-release preparations. It is also available in coformulation with other oral antidiabetic drugs (eg metformin plus glibenclimide).

Metformin accumulation is associated with a raised blood lactate concentration and metabolic acidosis, which may be profound and fatal. This can occur acutely in metformin poisoning or in unwell patients who take metformin at therapeutic doses. People who are elderly or have kidney impairment have a higher risk of metabolic acidosis.

High blood lactate concentration (hyperlactataemia) in the setting of metformin poisoning predicts worse prognosis, particularly in chronic accumulation (as opposed to acute poisoning).

Management of metformin poisoning aims to address severe metabolic acidosis if present. For large ingestions and ingestions of modified-release preparations, gastrointestinal decontamination with activated charcoal and whole bowel irrigation is recommended. A patient with hyperlactataemia, metabolic acidosis and systemic effects should be managed in a centre where haemodialysis is available.

For the management of poisoning due to coformulations of metformin, see advice for both drugs (eg for an ingestion of metformin plus glibenclamide, see also Sulfonylurea poisoning).