From the Guidelines
Type B lactic acidosis is a condition that requires prompt recognition and management to prevent progression to multi-organ failure, and the use of metformin should be avoided in patients at risk for lactic acidosis, such as those with significant renal impairment or liver failure, as evidenced by a recent study 1. The condition is characterized by the buildup of lactic acid in the bloodstream due to reasons other than tissue hypoxia, and common causes include liver disease, medications (like metformin), malignancies, thiamine deficiency, and certain metabolic disorders. Some key points to consider in the management of Type B lactic acidosis include:
- Measuring serum lactate levels (typically >4 mmol/L) and arterial blood gases showing metabolic acidosis with an increased anion gap for diagnosis
- Discontinuing the offending drug, such as metformin, in medication-induced cases
- Providing supportive care, including intravenous fluids, and considering bicarbonate therapy in severe cases, although its use remains controversial
- Being aware of the potential risks of metformin use, including lactic acidosis, particularly in patients with estimated glomerular filtration rate (eGFR) <30 mL/min/1.73 m², as highlighted in a recent study 1
- Monitoring kidney function and reassessing it before restarting metformin treatment, as recommended in the guidelines 1
- Considering alternative treatments, such as insulin or other glucose-lowering agents, in patients with severe hyperglycemia or those who require initiation or intensification of glucose-lowering therapy 1.
From the FDA Drug Label
5 WARNINGS AND PRECAUTIONS
- 1 Lactic Acidosis There have been postmarketing cases of metformin-associated lactic acidosis, including fatal cases. Metformin associated lactic acidosis was characterized by elevated blood lactate concentrations (>5 mmol/L), anion gap acidosis (without evidence of ketonuria or ketonemia), and an increased lactate: pyruvate ratio;
- Type B lactic acidosis is characterized by an increased lactate: pyruvate ratio, which is the type of lactic acidosis associated with metformin use.
- The elevated blood lactate concentrations (>5 mmol/L) and anion gap acidosis are key features of metformin-associated lactic acidosis.
- Metformin decreases liver uptake of lactate, increasing lactate blood levels, which may increase the risk of lactic acidosis, especially in patients at risk 2.
From the Research
Type B Lactic Acidosis
- Type B lactic acidosis is a rare but serious complication of metformin therapy, with a mortality rate of approximately 50% 3.
- It is characterized by high lactate levels and metabolic acidosis, and can be caused by metformin accumulation in the body 4, 5.
- The risk of developing type B lactic acidosis is increased in patients with renal failure, heart failure, and other underlying medical conditions 6, 3.
Treatment Options
- Hemodialysis is a effective treatment for type B lactic acidosis, and can help to remove metformin and lactate from the body 4, 5, 7.
- Continuous renal replacement therapy (CRRT) and continuous venovenous hemodiafiltration (CVVHDF) are also effective treatment options 6, 7.
- Sodium bicarbonate infusion can help to correct acid-base disorders and improve patient outcomes 4, 7.
Patient Outcomes
- With prompt and aggressive treatment, patients with type B lactic acidosis can make a complete recovery 5, 7.
- However, delayed treatment can lead to poor outcomes and high mortality rates 3.
- It is essential to suspect type B lactic acidosis in diabetic patients presenting with high anion gap metabolic acidosis and increased serum lactate levels, and to initiate treatment promptly 6.