Major
Iopromide × Metformin
X-ray contrast media. Watersoluble nephrotropic low-osmolar iodinated agents×Biguanides. Oral antihyperglycemic agents
Mechanism
Intravenous iodinated contrast media (iopromide) can cause acute kidney injury via osmotic load and direct toxicity. On metformin (renally excreted), plasma levels rise and lactic acidosis risk accumulates – a rare but life-threatening complication.
Symptoms
Lactic acidosis: dyspnoea, muscle pain, nausea, confusion, hypotension. Laboratory: blood pH below 7.35 and lactate above 5 mmol/L. Symptoms appear 1–3 days after contrast.
Management
For planned contrast studies, withhold metformin on the day of the procedure. Resume 48 hours later only with stable renal function (creatinine check before resuming). Alternative imaging in renal impairment: non-gadolinium MRI.