Metformin in peritoneal dialysis: a pilot experience

Metformin-associated lactic acidosis (MALA): Is it an underestimated entity? A retrospective, single-center case series

INTRODUCTION

Metformin is widely considered a first-line antiglycemic agent due to its cost-effectiveness and favorable adverse effect profile. However, its use is prohibited in patients with an estimated glomerular filtration rate <30 mL/min/1.73 m2 , due to the risk of potentially lethal metformin-associated lactic acidosis (MALA). We sought to evaluate MALA cases and outcomes at our institution.

METHODS

In this observational, retrospective case series, we reviewed our EMR for all patients who had a metformin level drawn between January 2013 and May 2022 to identify individuals who met the diagnostic criteria for MALA. We evaluated risk factors for MALA, the relationship between metformin level, blood pH, serum bicarbonate, and lactate level and clinical outcomes of ventilator dependency, renal replacement therapy requirement, renal recovery in acute kidney injury (AKI) patients, and survival.

FINDINGS

A total of 107 patients had metformin levels drawn, of which 19 patients met the diagnostic criteria for MALA. In our case series, MALA was primarily seen in AKI (15 patients) secondary to dehydration and sepsis, followed by end-stage renal disease (ESRD) (4 patients). Intubation was required in 17 patients, of whom 8 were successfully extubated after a mean duration of 14 days. Sixteen patients received renal replacement therapy (RRT). Intermittent hemodialysis (IHD) was performed in nine, continuous renal replacement therapy (CRRT) in four, and sequential therapy of IHD and CRRT in three patients. Seven patients, all in the AKI group (46.7%), died while all ESRD patients survived, accounting for an overall mortality rate of 36.8%. Among the eight surviving AKI patients, four had complete renal recovery with renal function returning to baseline, three had partial renal recovery, and one continued to require IHD at the time of discharge to a rehabilitation facility.

DISCUSSION

MALA may be an underrecognized entity. A high level of clinical suspicion leading to prompt and aggressive treatment with RRT may improve mortality rates. Provider and patient education is of paramount importance for safe use of metformin.

Shouldn't Stage 4 And 5 Chronic Kidney Disease Patients Use Metformin?

Metformin is the first place anti-diabetic agent recommended with life style changes in many guidelines for the treatment of patients with type 2 diabetes mellitus (DM). The mechanism of effect of the drug is to increase insulin sensitivity in peripheral tissue and reduce glucose secretion from the liver. Metformin is a low cost, effective and safe drug. Although its frequent side effects are gastrointestinal side effects and the most feared side effect is lactic acidosis. Due to this side effect, its use is limited in many guidelines in patients with chronic kidney disease (CKD). In this article, we examined the use of metformin in all stages of CKD. We investigated the incidence of metformin-associated lactic acidosis (MALA). Shouldn't stage 4 and 5 chronic kidney disease patients use metformin? We sought an answer to question. As a result, we decided that side effects like MALA are extremely rare. We observed that these side effects occur mostly in the presence of diseases in which tissue perfusion is impaired such as infections, serious cardiovascular events, and hypotension. We came to the conclusion that metformin should be used in patients with stage 4 and 5 CKD patients, without much fear, considering the profit and loss relationship.

Safety and effectiveness of metformin in patients with reduced renal function: A systematic review

AIM

To examine clinical and safety outcomes associated with metformin use in patients with impaired renal function.

MATERIALS AND METHODS

We searched PubMed and Embase databases from inception to August 2020, supplementing our search with a review of investigator files and reference lists of included studies. Any study reporting original data on metformin and patient-centred outcomes in patients with impaired renal function, defined as an estimated glomerular filtration rate (eGFR) of less than 60 mL/min/1.73m² , was included. Post hoc meta-analysis was performed for the outcomes of mortality, cardiovascular events and acidosis.

RESULTS

Nine small prospective studies enrolling patients with significantly impaired renal function identified only one case of clinically apparent lactic acidosis. Among 13 larger retrospective studies, seven examined the risk of mortality across patient subgroups; meta-analysis showed reductions in overall mortality at an eGFR of 45 mL/min/1.73m² or higher but not at an eGFR of less than 45 mL/min/1.73m² . Eight retrospective studies evaluated acidosis as an outcome; meta-analysis showed no increase in risk of acidosis except at an eGFR of less than 30 mL/min/1.73m² , in which group the HR was 1.97 (95% CI 1.03-3.77).

CONCLUSIONS

The literature shows metformin to be associated with reduced mortality and no increased risk of acidosis at an eGFR of 45 mL/min/1.73m² or higher. Metformin appears to be associated with fewer benefits and possible increases in the risk of acidosis at an eGFR of less than 30 mL/min/1.73m² . Consistent with US Food and Drug Administration guidelines, metformin should not be used at an eGFR less than 30 mL/min/1.73m² , and further research on its risk-benefit profile at eGFR values approaching 30 mL/min/1.73m² is warranted.

The Phantom of Metformin-Induced Lactic Acidosis in End-Stage Renal Disease Patients: Time to Reconsider with Peritoneal Dialysis Treatment

Objective

Metformin continues to be the safest and most widely used antidiabetic drug. In spite of its well-known benefits; metformin use in end-stage renal disease (ESRD) patients is still restricted. Little has been reported about the effect of peritoneal dialysis (PD) on metformin clearance and the phantom of lactic acidosis deprives ESRD patients from metformin therapeutic advantages. Peritoneal dialysis is probably a safeguard against lactic acidosis, and it is likely that using this drug would be feasible in this group of patients.

Material and methods

The study was conducted on 83 PD patients with type 2 diabetes mellitus. All patients were on automated PD (APD). Metformin was administered in a dose of 500 - 1,000 mg daily. Patients were monitored for glycemic control. Plasma lactic acid and plasma metformin levels were monitored on a scheduled basis. Peritoneal fluid metformin levels were measured. In addition, the relation between plasma metformin and plasma lactate was studied.

Results

Mean fasting blood sugar (FBS) was 10.9 ± 0.5 and 7.8 ± 0.7, and mean hemoglobin A1-C (HgA1C) was 8.2 ± 0.8 and 6.4 ± 1.1 at the beginning and end of the study, respectively (p < 0.001). The mean body mass index (BMI) was 29.1 ± 4.1 and 27.3 ± 4.5 at the beginning and at the end of the study, respectively (p < 0.001). The overall mean plasma lactate level across all blood samples was 1.44 ± 0.6. Plasma levels between 2 and 3 mmol/L were found in 11.8% and levels of 3 - 3.6 mmol/L in 2.4% plasma samples. Hyperlactemia (level > 2 and < 5 mmol/L) was not associated with overt acidemia. None of our patients had lactic acidosis (levels > 5 mmol/L). Age ≥ 60 was a predictor for hyperlactemia. No relationship was found between plasma metformin and lactate levels.

Conclusion

Metformin may be used with caution in a particular group of ESRD patients who are on APD. Metformin allows better diabetic control with significant reduction of BMI. Information on the relationship between metformin and plasma lactate levels is lacking. Peritoneal dialysis appears to be a safeguard against the development of lactic acidosis in this group of patients.

Is the use of metformin in patients undergoing dialysis hazardous for life? A systematic review of the safety of metformin in patients undergoing dialysis

AIMS

Metformin may have clinical benefits in dialysis patients; however, its safety in this population is unknown. This systematic review evaluated the safety of metformin in dialysis patients.

METHODS

MEDLINE, Embase, CENTRAL, PsycINFO and the Cochrane Library were searched for randomised controlled trials and observational studies evaluating metformin use in dialysis patients. Three authors reviewed the studies and extracted data. The primary outcomes were mortality, occurrence of lactic acidosis and myocardial infarction (MI) in patients taking metformin during dialysis treatment for ≥12 months (long term). Risk of bias was assessed using Risk Of Bias In Nonrandomised Studies of Interventions (ROBINS-1). Overall quality of evidence was assessed using Grading of Recommendations Assessment, Development and Evaluation (GRADE).

RESULTS

Fifteen observational studies were eligible; 7 were prospective observational studies and 8 were case reports/case series. No randomised controlled trials were identified. The 7 prospective observational studies (n = 194) reported on cautious metformin use in patients undergoing maintenance dialysis. Only 3 provided long-term follow-up data. In 2 long-term studies of metformin therapy (≤1000 mg/d) in patients undergoing peritoneal dialysis (PD), 1 reported 6 deaths (6/83; 7%) due to major cardiovascular events (3 MI) and the other reported no deaths (0/35). One long-term study of metformin therapy (250 mg to 500 mg thrice weekly) in patients undergoing haemodialysis reported 4 deaths (4/61; 7%) due to major cardiovascular events (2 MI). These findings provide very low-quality evidence as they come from small observational studies.

CONCLUSION

The evidence regarding the safety of metformin in people undergoing dialysis is inconclusive. Appropriately designed randomised controlled trials are needed to resolve this uncertainty.

Lactate Levels with Chronic Metformin Use: A Narrative Review

Metformin has been associated with lactic acidosis. Lactate levels are not commonly tested in clinical practice, and it is unclear to what extent metformin would typically increase lactate levels with chronic use. The aim of this review was to determine whether regular monitoring of the plasma lactate level would be beneficial in avoiding lactate accumulation and, ultimately, minimising the incidence of lactic acidosis in metformin-treated patients.A comprehensive search of PubMed, Embase, Web of Science, Cochrane and International Pharmaceutical Abstracts databases covering the period up to 30 May 2017 was performed. Search terms included combinations of terms and keywords, including "metformin", "lactate", "lactic acid" and "lactic acidosis". Cases series of lactic acidosis or metformin-associated lactic acidosis were excluded.Of 1539 potentially relevant articles, a total of 52 reported lactate levels from routine/regular pathological tests in metformin users. The studies were subdivided into four themes, regarding metformin usage and the reported lactate levels in patients who: (1) did not have contraindications to the use of metformin; (2) had contraindications, or renal impairment but without other contraindications; (3) exercised; or (4) also received any nucleoside reverse transcriptase inhibitor. Studies have reported that metformin treatment could increase lactate level of users. However, most results showed that the lactate level remained in the normal range.No definitive conclusions on the benefits of regular lactate monitoring in patients taking metformin can be made. Future research on larger populations focusing on the measurement of lactate levels with continuous metformin use is warranted.

Association Between Stroke Risk and Metformin Use in Hemodialysis Patients With Diabetes Mellitus: A Nested Case-Control Study

BACKGROUND

Metformin use reduces the incidence and severity of stroke in patients with type 2 diabetes mellitus (DM). The benefits of metformin for stroke have not been examined in hemodialysis patients with DM.

METHODS AND RESULTS

Using the National Health Insurance Research Database, we identified 17 760 patients with DM and new-onset hemodialysis between 2001 and 2013. Of these, 1898 patients hospitalized for either ischemic or hemorrhagic stroke were matched to 7592 control patients according to sex, age, and year of initial hemodialysis therapy by using incidence sampling. The association between metformin use and stroke risk was estimated using conditional logistic regression after adjustment for hemodialysis frequency, comorbidity, and prescribed medications. Metformin use was recorded before the date of stroke admission and the date of pseudostroke of the case and control patients, respectively. Results showed that hemodialysis patients with ischemic stroke were more likely to use metformin than the controls 1 year before the date of stroke admission (adjusted odds ratio: 1.64; 95% confidence interval, 1.32-2.04). The association was evident within 90 days before the index date (adjusted odds ratio: 1.81; 95% confidence interval, 1.27-2.60). The results were consistent with those of hemodialysis patients with hemorrhagic stroke. Metformin use remained a risk factor for stroke in patients treated with antihypertensive, sulfonylurea, and antiplatelet drugs.

CONCLUSIONS

This nested case-control study is the first to show that metformin use is associated with stroke risk in hemodialysis patients with DM. We suggest that metformin should not be used by hemodialysis patients with DM.

Metformin ameliorates the Phenotype Transition of Peritoneal Mesothelial Cells and Peritoneal Fibrosis via a modulation of Oxidative Stress

Phenotype transition of peritoneum is an early mechanism of peritoneal fibrosis. Metformin, 5′-adenosine monophosphate-activated protein kinase (AMPK) activator, has recently received a new attention due to its preventive effect on organ fibrosis and cancer metastasis by inhibiting epithelial-to-mesenchymal transition (EMT). We investigated the effect of metformin on EMT of human peritoneal mesothelial cells (HPMC) and animal model of peritoneal dialysis (PD). TGF-β1-induced EMT in HPMC was ameliorated by metformin. Metformin alleviated NAPDH oxidase- and mitochondria-mediated ROS production with an increase in superoxide dismutase (SOD) activity and SOD2 expression. Metformin inhibited the activation of Smad2/3 and MAPK, GSK-3β phosphorylation, nuclear translocalization of β-catenin and Snail in HPMCs. Effect of metformin on TGF-β1-induced EMT was ameliorated by either AMPK inhibitor or AMPK gene silencing. Another AMPK agonist, 5-amino-1-β-D-ribofuranosyl-imidazole-4-carboxamide partially blocked TGF-β1-induced EMT. In animal model of PD, intraperitoneal metformin decreased the peritoneal thickness and EMT with an increase in ratio of reduced to oxidized glutathione and the expression of SOD whereas it decreased the expression of nitrotyrosine and 8-hydroxy-2′-deoxyguanosine. Therefore, a modulation of AMPK in peritoneum can be a novel tool to prevent peritoneal fibrosis by providing a favorable oxidant/anti-oxidant milieu in peritoneal cavity and ameliorating phenotype transition of peritoneal mesothelial cells.

Extending Metformin Use in Diabetic Kidney Disease: A Pharmacokinetic Study in Stage 4 Diabetic Nephropathy

INTRODUCTION

Metformin use in advanced chronic kidney disease is controversial. This study sought to examine the pharmacokinetics, safety, and efficacy of low-dose metformin in patients with type 2 diabetes and stage 4 chronic kidney disease.

METHODS

In this open-label, phase I trial, 3 consecutive cohorts (1, 2, and 3) of 6 patients each were recruited to receive 250-, 500-, or 1000-mg once-daily doses of metformin, respectively. All patients underwent a first-dose pharmacokinetic profile and weekly trough metformin concentrations for the duration of 4 weeks of daily therapy. Prespecified clinical and biochemical safety endpoints of serum bicarbonate, venous pH, and serum lactate were assessed weekly. Efficacy was assessed by pre- and post-HbA1c and 72-hour capillary glucose monitoring.

RESULTS

There was no evidence of accumulation of metformin in any cohort. There were no episodes of hyperlactatemia or metabolic acidosis and no significant change in any biochemical safety measures. Median (interquartile range) observed trough concentrations of metformin in cohorts 1, 2, and 3 were 0.083 (0.121) mg/l, 0.239 (0.603) mg/l, and 1.930 (3.110) mg/l, respectively. Average capillary glucose concentrations and mean HbA1c decreased in all cohorts.

DISCUSSION

In our patient cohorts with diabetes and stage 4 chronic kidney disease, treatment with 4 weeks of low-dose metformin was not associated with adverse safety outcomes and revealed stable pharmacokinetics. Our study supports the liberalization of metformin use in this population and supports the use of metformin assays for more individualized dosing.

Could metformin be used in patients with diabetes and advanced chronic kidney disease?

Diabetes is an important cause of end stage renal failure worldwide. As renal impairment progresses, managing hyperglycaemia can prove increasingly challenging, as many medications are contra-indicated in moderate to severe renal impairment. Whilst evidence for tight glycaemic control reducing progression to renal failure in patients with established renal disease is limited, poor glycaemic control is not desirable, and is likely to lead to progressive complications. Metformin is a first-line therapy in patients with Type 2 diabetes, as it appears to be effective in reducing diabetes related end points and mortality in overweight patients. Cessation of metformin in patients with progressive renal disease may not only lead to deterioration in glucose control, but also to loss of protection from cardiovascular disease in a cohort of patients at particularly high risk. We advocate the need for further study to determine the role of metformin in patients with severe renal disease (chronic kidney disease stage 4-5), as well as patients on dialysis, or pre-/peri-renal transplantation. We explore possible roles of metformin in these circumstances, and suggest potential key areas for further study.

Extracorporeal Treatment for Metformin Poisoning: Systematic Review and Recommendations From the Extracorporeal Treatments in Poisoning Workgroup

BACKGROUND

Metformin toxicity, a challenging clinical entity, is associated with a mortality of 30%. The role of extracorporeal treatments such as hemodialysis is poorly defined at present. Here, the Extracorporeal Treatments In Poisoning workgroup, comprising international experts representing diverse professions, presents its systematic review and clinical recommendations for extracorporeal treatment in metformin poisoning.

METHODS

A systematic literature search was performed, data extracted, findings summarized, and structured voting statements developed. A two-round modified Delphi method was used to achieve consensus on voting statements and RAND/UCLA Appropriateness Method to quantify disagreement. Anonymized votes and opinions were compiled and discussed. A second vote determined the final recommendations.

RESULTS

One hundred seventy-five articles were identified, including 63 deaths: one observational study, 160 case reports or series, 11 studies of descriptive cohorts, and three pharmacokinetic studies in end-stage renal disease, yielding a very low quality of evidence for all recommendations. The workgroup concluded that metformin is moderately dialyzable (level of evidence C) and made the following recommendations: extracorporeal treatment is recommended in severe metformin poisoning (1D). Indications for extracorporeal treatment include lactate concentration greater than 20 mmol/L (1D), pH less than or equal to 7.0 (1D), shock (1D), failure of standard supportive measures (1D), and decreased level of consciousness (2D). Extracorporeal treatment should be continued until the lactate concentration is less than 3 mmol/L (1D) and pH greater than 7.35 (1D), at which time close monitoring is warranted to determine the need for additional courses of extracorporeal treatment. Intermittent hemodialysis is preferred initially (1D), but continuous renal replacement therapies may be considered if hemodialysis is unavailable (2D). Repeat extracorporeal treatment sessions may use hemodialysis (1D) or continuous renal replacement therapy (1D).

CONCLUSION

Metformin poisoning with lactic acidosis appears to be amenable to extracorporeal treatments. Despite clinical evidence comprised mostly of case reports and suboptimal toxicokinetic data, the workgroup recommended extracorporeal removal in the case of severe metformin poisoning.

Antidiabetic therapy in post kidney transplantation diabetes mellitus

Post-transplantation diabetes mellitus (PTDM) is a common complication after kidney transplantation that affects up to 40% of kidney transplant recipients. By pathogenesis, PTDM is a diabetes form of its own, and may be characterised by a sudden, drug-induced deficiency in insulin secretion rather than worsening of insulin resistance over time. In the context of deteriorating allograft function leading to a re-occurrence of chronic kidney disease after transplantation, pharmacological interventions in PTDM patients deserve special attention. In the present review, we aim at presenting the current evidence regarding efficacy and safety of the modern antidiabetic armamentarium. Specifically, we focus on incretin-based therapies and insulin treatment, besides metformin and glitazones, and discuss their respective advantages and pitfalls. Although recent pilot trials are available in both prediabetes and PTDM, further studies are warranted to elucidate the ideal timing of various antidiabetics as well as its long-term impact on safety, glucose metabolism and cardiovascular outcomes in kidney transplant recipients.

A justification for less restrictive guidelines on the use of metformin in stable chronic renal failure

AIM

The aim was to justify less restrictive use of metformin in stable chronic renal failure, because a literature review reveals metformin is associated with a significantly lower incidence of cardiovascular events and mortality compared with other hypoglycaemic agents, and metformin-associated lactic acidosis is rare and causation uncertain. Studies on intentional metformin overdose and metformin bioavailability, renal clearance and plasma metformin in renal impairment provide evidence in support of a less restrictive use of metformin.

METHODS

In metformin overdose (n = 22), lactic acidosis was not inevitable with a plasma metformin > 40 mg/l (therapeutic level c. 1 mg/l): Severe lactic acidosis (pH ≤ 7.21, plasma lactate ≥ 11 mmol/l, n = 8) did not occur unless plasma metformin was > 40 mg/l. Plasma lactate was a more consistent predictor of pH than plasma metformin, with plasma lactate ≤ 4.7 being associated with a pH ≥ 7.34. A likely 'safe' plasma lactate is < 3.5 mmol/l and plasma metformin < 10 mg/l.

RESULTS

Plasma metformin can be predicted from estimated glomerular filtration rate and metformin dose. Reported plasma metformin in renal failure was always less than predicted plasma metformin. Predicted plasma metformin (mg/l), with an estimated glomerular filtration rate of 30 ml/min and metformin 2000 mg/day was 6.8; an estimated glomerular filtration rate of 20 ml/min and metformin 1500 mg/day was 5.1; an estimated glomerular filtration rate of 10 ml/min and metformin 500 mg/day was 4.4.

CONCLUSION

Metformin accumulates in renal failure and, although accumulation does not always lead to lactic acidosis, dose modification to achieve a predicted plasma metformin < 10 mg/l is suggested. As plasma metformin is not routinely available, plasma lactate should be useful in monitoring the use of metformin in renal failure.

Metformin in chronic kidney disease: time for a rethink

Metformin has traditionally been regarded as contraindicated in chronic kidney disease (CKD), though guidelines in recent years have been relaxed to permit therapy if the glomerular filtration rate (GFR) is > 30 mL/min. The main problem is the perceived risk of lactic acidosis (LA). Epidemiological evidence suggests that this fear is disproportionate. Lactic acidosis is a rare complication to type 2 diabetes mellitus (T2DM), with an incidence of 6/100,000 patient-years. The risk is not increased in metformin-treated patients. Metformin possesses a number of clinical effects independent of glucose reduction, including weight loss, which are beneficial to patients. The risk of death and cardiovascular disease is reduced by about a third in non-CKD patients. Since metformin intoxication undoubtedly causes LA, and metformin is renally excreted, inappropriate dosage of metformin will increase the risk of LA. It is suggested that introduction of metformin therapy to more advanced stages of CKD may bring therapeutic benefits that outweigh the possible risks.