[Metformin-associated lactic acidosis remains a serious complication of metformin therapy]

Fatal metformin overdose: case report and postmortem biochemistry contribution

Metformin is an oral antihyperglycemic agent used in the management of type 2 diabetes mellitus. Lactic acidosis from metformin overdose is a rare complication of metformin therapy and occurs infrequently with therapeutic use. Fatal cases, both accidental and intentional, are extremely rare in clinical practice. Metformin is eliminated by the kidneys, and impaired renal function can result in an increased plasma concentration of the drug. In this report, we describe an autopsy case involving a 70-year-old woman suffering from diabetes mellitus and impaired renal function who received metformin treatment. Metformin concentrations in the peripheral blood collected during hospitalization and femoral blood collected during autopsy were 42 and 47.3 µg/ml, respectively. Lactic acidosis (29.10 mmol/l) was objectified during hospitalization. Furthermore, postmortem biochemistry allowed ketoacidosis to be diagnosed (blood β-hydroxybutyrate, 10,500 µmol/l). Death was attributed to lactic acidosis due to metformin intoxication. Increased plasma concentrations of the drug were attributed to severely impaired renal function. The case emphasizes the usefulness of performing exhaustive toxicology and postmortem biochemistry towards the more complete understanding of the pathophysiological mechanisms that may be involved in the death process.

Metformin overdose: time to move on

Does metformin-associated lactic acidosis really exist? Despite an old controversy, there is no doubt about it. But do we understand what is going on? Laboratory findings raised several hypotheses explaining the pathophysiology of this disease. The main cause could be an inhibition of either gluconeogenesis or mitochondrial respiratory chain complex I. From bench to bedside, one hypothesis is now confirmed in humans. Metformin poisoning involves, at least partially, a mitochondrial dysfunction.

The gonadal hormone regulates the plasma lactate levels in type 2 diabetes treated with and without metformin

OBJECTIVE

Our previous study showed there was a gender difference in plasma lactate concentrations in subjects with type 2 diabetes. This study investigated the effect of sex hormone levels on plasma lactic acid (LA) levels in type 2 diabetes with and without metformin therapy.

SUBJECTS AND METHODS

Fasting whole blood specimens of 392 type 2 diabetes patients treated with metformin (n=199) or not (n=193) were collected. LA was measured with an enzyme-electrode assay. Levels of sex hormones, including testosterone (T) and estradiol (E(2)), were measured with a chemiluminescence microparticle immunoassay. Spearman's or Pearson's correlation and logistic regression analysis were performed for the factors associated with LA.

RESULTS

The LA level in the metformin group was significantly higher than that in the non-metformin group (1.26±0.43 vs. 1.14±0.49 mmol/L, P<0.001), and LA levels of females were significantly higher than those of males (P<0.001). LA concentrations were positively correlated with E(2) level but negatively correlated with metformin and T levels (P<0.01). The logistic regression analysis showed that gender, creatinine, E(2), metformin, and T were independent factors influencing lactate levels. Analysis of subgroups demonstrated that the LA concentrations increased with the elevation of E(2) level (P<0.05) but decreased with the rising of T level (P<0.05).

CONCLUSIONS

Sex hormones play an important role on regulating plasma lactate levels in diabetes patients treated with metformin. E(2) up-regulates but T tend to down-regulate lactate levels.

Metformin and lactic acidosis in patients with type 2 diabetes--from pride and prejudice to sense and sensibility

AIM

To present the cases of lactic acidosis encountered in our department among metformin-treated type 2 diabetic patients and to investigate the role of contraindications to metformin use.

METHODS

A survey of medical records of metformin-treated type 2 diabetic patients hospitalised for various medical conditions during the years 2004-2005 who exhibited elevated serum concentrations of lactic acid.

RESULTS

Seven metformin-treated type 2 diabetic patients were identified who were not attending our department and were hospitalised with elevated serum lactic acid levels (6 developed lactic acidosis). All patients had one or more contraindications to metformin use. Outcome was favourable in 6 patients, while 1 patient with hepatocellular carcinoma died of liver failure.

CONCLUSIONS

So far, metformin is one of the safest first-line oral hypoglycaemic agents. However, caution is needed to avoid patients with evident contraindications. This highlights the need for the practitioner to possess sound clinical judgement when prescribing metformin.

[Metabolic acidosis in a context of acute severe asthma]

In a context of asthma, lactic acidosis may occur during beta2-agonist therapy. Several cases have been reported during its administration by intravenous and/or inhaled route. This side-effect seems rather unknown and the mechanism for compensation of metabolic acidosis by hyperventilation may worsen dyspnoea and mislead clinicians. Other causes of lactic acidosis such as a major hypoxemia, a cardiovascular collapse or sepsis may also be experienced in this context and must be ruled out before attributing the lactic acidosis to beta2-agonist treatment. We report the case of a 50-year-old man hospitalized for an acute major asthma, who received a salbutamol continuous infusion associated with inhaled terbutaline. A serum lactate level of 13 mmol/l was noted eight hours after the introduction of the bronchodilator treatment. After reducing doses of beta2-agonists, the evolution was favourable, regarding both respiratory and metabolic aspects, with a rapid decrease of the serum lactate level, which finally returned to normal level after 32 hours of hospitalization.

Acidose lactique et metformine

OBJECTIVE

The aims of this review are to precise the pathophysiological mechanisms leading to biguanide-associated lactic acidosis, to give elements of diagnosis, and to underline the precautionary conditions for prescribing these drugs by an improvement in physicians and patient's education.

DATA SOURCES

A PubMed database research in English and French language reports published until December 2005. The keywords were: lactic acidosis, metformin, biguanide, diabetes mellitus.

DATA EXTRACTION

Data in selected articles were reviewed, clinical and basic science research relevant informations were extracted.

DATA SYNTHESIS

Metformin, which is an oral antidiabetic agent, is the only one biguanide available in France. It acts by enhancing the sensitivity to insulin by a decrease in the hepatic glucose production and an increase in its peripheral use. In term of glycemic control, it has the same efficiency than the other hypoglycemic agents. It represents the treatment of choice for overweight type 2 diabetic patients because of its beneficial effects on the weight loss and on the cardiovascular complications. The incidence of metformin-associated lactic acidosis is very low when contra-indications and appropriate rules for prescribing this drug are respected. The relationship between metformin and lactic acidosis remains largely controversial. In practical, we can distinguish three situations which have different prognosis. In the first case, metformin seems to be responsible for lactic acidosis because of self-poisoning or accidental overdose, and prognosis is good. In the second case, the association between metformin and lactic acidosis is coincidental rather than causal, and may be induced by an underlying organ failure. In the last case there is a cause of lactic acidosis which is worsened by a precipitating factor leading to metformin accumulation. The 2 latter situations are very severe as mortality rate is about 50%. Symptomatic treatments and renal replacement therapy which allows metformin removal are the curative treatment. Prevention is essential. It requires the respect of metformin contraindications and a better education of physicians and patients for a safe prescription.

CONCLUSION

Due to its beneficial effects, metformin is the gold standard treatment for overweight type 2 diabetic patients. The essential precautionary conditions for prescribing metformin as well as the respect of its contra-indications permit largely to prevent lactic acidosis. This complication is serious when it is associated with intercurrent illnesses and metformin accumulation. The curative treatment is based on renal replacement therapy. Prevention only rests on the respect of the contra-indications. Education of physicians and patients concerning the rules of prescription remains essential.