Warning

Lactic Acidosis
• Lactic acidosis rare but potentially fatal.^{1 6 18 20 27 29 30 62 89 96 158 234 254} Increased risk of lactic acidosis in patients with renal impairment and advanced age.^{1 2 62 96 119 234 254 260 314 352 355 361}

• Generally has occurred in diabetic patients with severe renal insufficiency and concomitant medical and/or surgical problems who were receiving multiple drugs; metformin plasma concentrations >5 mcg/mL often found in patients with lactic acidosis.^{1 2 3 20 50 62 64 76 96 123 158 164 165 234 254 314}

• Periodically monitor renal function and use the minimum effective dosage.^{1 32 62 63 65 76 85 91 93 96 119 123 124 158 164 165 234 254 258 287 314} Withhold metformin promptly in patients with any condition associated with hypoxemia, sepsis, or dehydration.^{1 2 62 63 93 234 260 314 340} Avoid use in patients with clinical or laboratory evidence of hepatic impairment.^{1 2 63 65 85 91 93 156 158 234 254 314 352 355} Manufacturers state to temporarily discontinue metformin therapy before or at the time of an intravascular (e.g., IV, intra-arterial) iodinated contrast imaging procedure in patients with eGFR of 30–60 mL/minute per 1.73 m² and in patients with a history of liver disease, alcoholism, or heart failure.^{1 234 254 330 336 352 355 610} Withhold metformin temporarily in patients undergoing surgery. ^{1 2 30 62 63 93 158 234 254 261 314 330 336 352 355 610} Concomitant drugs that may affect renal function, produce substantial hemodynamic changes, or alter metformin elimination should be used with caution.^{1 134 234 254}

  However, the American College of Radiology states that in patients with no evidence of acute kidney injury and eGFR ≥30 mL/minute per 1.73 m², no need to discontinue metformin either before or following the administration of iodinated contrast media, nor is there a need to reassess the patient's renal function after the test or procedure.³³⁵

• Advise patients not to consume excessive amounts of alcohol, acutely or chronically.^{1 2 63 76 91 93 158 234 314 352 355}

• If lactic acidosis occurs, discontinue metformin and institute general supportive therapy immediately.^{1 30 260 314} Treat as medical emergency, with immediate hospitalization and treatment required; prompt hemodialysis recommended.^{1 23 32 62 117 119 234 254 260 314 352 355}