Biguanide-induced lactic acidosis in Finland

Do Patients Die with or from Metformin-Associated Lactic Acidosis (MALA)? Systematic Review and Meta-analysis of pH and Lactate as Predictors of Mortality in MALA

OBJECTIVES

Metformin-associated lactic acidosis (MALA) may occur after acute metformin overdose, or from therapeutic use in patients with renal compromise. The mortality is high, historically 50% and more recently 25%. In many disease states, lactate concentration is strongly associated with mortality. The aim of this systematic review and meta-analysis is to investigate the utility of pH and lactate concentration in predicting mortality in patients with MALA.

METHODS

We searched PubMed, EMBASE, and Web of Science from their inception to April 2019 for case reports, case series, prospective, and retrospective studies investigating mortality in patients with MALA. Cases and studies were reviewed by all authors and included if they reported data on pH, lactate, and outcome. Where necessary, authors of studies were contacted for patient-level data. Receiver operating characteristic (ROC) curves were generated for pH and lactate for predicting mortality in patients with MALA.

RESULTS

Forty-four studies were included encompassing 170 cases of MALA with median age of 68.5 years old. Median pH and lactate were 7.02 mmol/L and 14.45 mmol/L, respectively. Overall mortality was 36.2% (95% CI 29.6-43.94). Neither lactate nor pH was a good predictor of mortality among patients with MALA. The area under the ROC curve for lactate and pH were 0.59 (0.51-0.68) and 0.43 (0.34-0.52), respectively.

CONCLUSION

Our review found higher mortality from MALA than seen in recent studies. This may be due to variation in standard medical practice both geographically and across the study interval, sample size, misidentification of MALA for another disease process and vice versa, confounding by selection and reporting biases, and treatment intensity (e.g., hemodialysis) influenced by degree of pH and lactate derangement. The ROC curves showed poor predictive power of either lactate or pH for mortality in MALA. With the exception of patients with acute metformin overdose, patients with MALA usually have coexisting precipitating illnesses such as sepsis or renal failure, though lactate from MALA is generally higher than would be considered survivable for those disease states on their own. It is possible that mortality is more related to that coexisting illness than MALA itself, and many patients die with MALA rather than from MALA. Additional work looking solely at MALA in healthy patients with acute metformin overdose may show a closer relationship between lactate, pH, and mortality.

Symptomatic hyperlactataemia precipitated by the addition of tetracycline to combination antiretroviral therapy

Hyperlactataemia in the setting of combination antiretroviral therapy for HIV infection occurs on a spectrum ranging from common, asymptomatic laboratory abnormalities to rare, potentially life-threatening lactic acidosis. Some other medications, including the biguanides, tetracycline, and even linezolid, have rarely been reported to cause lactic acidosis. Recently, cases of lactic acidosis or hyperlactataemia have been reported in patients receiving combination antiretroviral therapy that have been precipitated by the addition of other medications-eg, metformin or ribavirin. We report a case of symptomatic hyperlactataemia in a patient on combination antiretroviral therapy that was likely precipitated by the addition of tetracycline and discuss the broader implications of other medications with the potential to cause hyperlactataemia in the setting of combination antiretroviral therapy.

Metformin and lactic acidosis: cause or coincidence? A review of case reports

OBJECTIVE

Metformin has been associated with the serious side-effect lactic acidosis. However, it remains unclear whether the use of metformin was a cause or a coincidence in lactic acidosis.

DESIGN

A literature search of the Index Medicus (1959-66) and of the databases Embase, Medline, Medline Express (1966-99) was performed using the keywords metformin, biguanides and lactic acidosis. All articles of cases with metformin-induced lactic acidosis (MILA) were cross-referenced.

SUBJECTS

Cases were included for analysis if they met the following criteria: serum pH < or =7.35, lactate concentration > or =5 mmol L(-1).

INTERVENTION

A forum of six experts in intensive care medicine independently categorized the cases in MILA unlikely (score 0), possible MILA (score 1) or probable MILA (score 2).

MAIN OUTCOME MEASURES

Statistical analysis included the paired interobserver agreement (kappa) and multivariate regression analysis.

RESULTS

Of 80 reported cases, 33 were excluded because of insufficient quality. The forum scores of the remaining 47 cases were distributed normally with a mean score of 7 (range 2-10). The kappa-value was 0.041 (SD = 0.24, range -0.514, 0.427). Neither lactate concentration nor mortality correlated with serum metformin concentrations.

CONCLUSIONS

Given the low interobserver agreement and the lack of any relationship between metformin levels and outcome parameters, the concept that there is a simple, causal relationship between metformin use and lactic acidosis in diabetic patients has to be reconsidered.

Drug and chemical-induced metabolic acidosis

Metabolic acidosis produced by drugs and/or chemicals can be conveniently divided into those with an increase in the anion gap (anion gap = Na- (Cl + HCO3)) and those with a normal anion gap. The increase in the anion gap is due to the accumulation of unmeasured organic anions, such as lactate or acetoacetate and beta-hydroxybutyrate, as occurs in ketoacidosis and lactic acidosis, or the accumulation of toxic anions such as formate or glycolate, as occurs with the ingestion of methanol or ethylene glycol. Increased concentrations of lactic acid may also be present in the toxic forms of metabolic acidosis. The most common drugs and chemicals that induce the anion gap type of acidosis are biguanides, alcohols, polyhydric sugars, salicylates, cyanide and carbon monoxide. In normal anion gap acidosis the reduction in bicarbonate is balanced by a reciprocal increase in the chloride concentration so that the sum of the two remains unchanged. Normal anion gap acidosis is caused by carbonic anhydrase inhibitors, hydrochloride salts of amino acids, toluene, amphotericin, spironolactone and non-steroidal anti-inflammatory drugs. The mechanism by which these substances produce metabolic acidosis and the therapy are discussed.

Effect of discontinuation of biguanide therapy on metabolic control in maturity-onset diabetics

Control of blood-glucose levels was monitored for 12 wk after withdrawal of biguanides in a group of 118 diabetic patients treated with biguanides (alone or in combination with sulphonylurea) from a population of 39,200. The mean fasting blood-glucose level rose during the first 2 wk from 9.2 +/- 0.3 to 11.3 +/- 0.4 mmol/l (p less than 0.001) and the mean urinary-glucose excretion from 11.7 +/- 3.7 g/24 h to 36.5 +/- 5.5 g/24 h (p less than 0.001), respectively. The change in blood-glucose concentration did not depend on age, sex, bodyweight, or duration of diabetes or biguanide treatment. The mean increase in blood-glucose was similar (2.1-3.1 mmol/l) in subjects with their initial blood-glucose level less than or equal to 6.0 mmol/l, 6.1-11.0 mmol/l, and greater than or equal to 11.1 mmol/l. There were no changes in blood-lipids or bodyweight during the observation period. Biguanides reduced blood-glucose levels in most patients with maturity-onset diabetes. The hypoglycaemic effect was similar in subjects with normal and increased bodyweight and did not depend on the duration or severity of diabetes.