Metformin-associated lactic acidosis (MALA) is a rare but serious adverse drug reaction (ADR). The aim of the study was to identify clinical situations associated with the onset of MALA in patients hospitalised in the Nord Pas de Calais regional intensive care units (ICUs), and to assess its preventability.

We included all cases of MALA, identified by metformin accumulation >2.3mg/dL and lactate >2.2mmol/L, reported by the regional ICU physicians to the Regional Centre of Pharmacovigilance and registered in the French Pharmacovigilance Database between 1 January 2017 and 30 December 2018.

One hundred and ninety-eight (198) cases of MALA were included. 38 patients died in direct association with MALA (19.2%). There was a correlation between metformin plasma accumulation and acute renal failure and with the severity of MALA (P<0.0001). All patients presented an acute intercurrent event favouring MALA, dehydration for 87 (43.9%) patients, severe infection for 65 (32.8%) patients. For 172 patients (86.7%), the prescription was not adapted to the intercurrent medical situation as recommended. Seventy (40.5%) patients consulted their general practitioner for the acute intercurrent event, 1 temporarily stopped metformin and 34.3% had been referred directly to hospital. The remaining 65.7% presented to the hospital around 4 days later due to worsening symptoms. MALA was identified as preventable in 160 patients (80.8%).

MALA in ICUs often follow acute dehydration or infection, and these high-risk situations must be signals to prevent this serious ADR. Specific education programmes for physicians and patients could also reduce this risk.