Metformin: mechanisms of antihyperglycemic action, other pharmacodynamic properties, and safety perspectives

Metformin: A Prospective Alternative for the Treatment of Chronic Pain

Metformin (biguanide) is a drug widely used for the treatment of type 2 diabetes. This drug has been used for 60 years as a highly effective antihyperglycemic agent. The search for the mechanism of action of metformin has produced an enormous amount of research to explain its effects on gluconeogenesis, protein metabolism, fatty acid oxidation, oxidative stress, glucose uptake, autophagy and pain, among others. It was only up the end of the 1990s and beginning of this century that some of its mechanisms were revealed. Metformin induces its beneficial effects in diabetes through the activation of a master switch kinase named AMP-activated protein kinase (AMPK). Two upstream kinases account for the physiological activation of AMPK: liver kinase B1 and calcium/calmodulin-dependent protein kinase kinase 2. Once activated, AMPK inhibits the mechanistic target of rapamycin complex 1 (mTORC1), which in turn avoids the phosphorylation of p70 ribosomal protein S6 kinase 1 and phosphatidylinositol 3-kinase/protein kinase B signaling pathways and reduces cap-dependent translation initiation. Since metformin is a disease-modifying drug in type 2 diabetes, which reduces the mTORC1 signaling to induce its effects on neuronal plasticity, it was proposed that these mechanisms could also explain the antinociceptive effect of this drug in several models of chronic pain. These studies have highlighted the efficacy of this drug in chronic pain, such as that from neuropathy, insulin resistance, diabetic neuropathy, and fibromyalgia-type pain. Mounting evidence indicates that chronic pain may induce anxiety, depression and cognitive impairment in rodents and humans. Interestingly, metformin is able to reverse some of these consequences of pathological pain in rodents. The purpose of this review was to analyze the current evidence about the effects of metformin in chronic pain and three of its comorbidities (anxiety, depression and cognitive impairment).

Metabolic targets for cancer therapy

Malignant cells exhibit metabolic changes, when compared to their normal counterparts, owing to both genetic and epigenetic alterations. Although such a metabolic rewiring has recently been indicated as yet another general hallmark of cancer, accumulating evidence suggests that the metabolic alterations of each neoplasm represent a molecular signature that intimately accompanies and allows for different facets of malignant transformation. During the past decade, targeting cancer metabolism has emerged as a promising strategy for the development of selective antineoplastic agents. Here, we discuss the intimate relationship between metabolism and malignancy, focusing on strategies through which this central aspect of tumour biology might be turned into cancer's Achilles heel.

Suicide commitment with metformin: our experience with five cases

Biguanides can function as oral antihyperglycemic drugs. They were used for diabetes mellitus or prediabetes treatment over the last nine decades, but they lost their popularity in 1970s because of phenformin and regained with metformin. For metformin, the most common side effects are diarrhea and dyspepsia, occurring in up to 30% of patients. The most important and serious side effect is lactic acidosis. Phenformin was removed from the markets before 1970, because it caused lactic acidosis in 40-65 patients in 100,000 patient-years. Metformin causes lactate accumulation only in patients who have hepatic failure, renal failure or in patients who attempt suicide with high dosage of drugs. In this report, we present five patients who used high doses of metformin for suicide attempt.

Should dialysis be offered in all cases of metformin-associated lactic acidosis?

Metformin is commonly used in diabetes mellitus type 2, with lactic acidosis being a rare but potentially fatal complication of this therapy. The management of metformin-associated lactic acidosis (MALA) is controversial. Treatment may include supportive care, activated charcoal, bicarbonate infusion, hemodialysis, or continuous venovenous hemofiltration. In the previous issue of Critical Care, Peters and colleagues systematically evaluated outcomes in MALA patients admitted to their intensive care unit. The mortality rate of patients who received dialysis was similar to that of patients who were not dialyzed. However, it was the more acutely and chronically ill patients who actually received dialysis. This suggests that hemodialysis was beneficial in preventing a higher mortality rate in those who required renal replacement therapy.

Dialysis Rounds A Dialysis Case Presentation and Discussion Edited by Roger A. Rodby: Severe Lactic Acidosis Treated with Prolonged Hemodialysis: Recovery After Massive Overdoses of Metformin

We report two cases of severe lactic acidosis due to massive metformin ingestion. The first case was a 37-year-old man who was discovered several hours after ingesting 45 g of metformin. He had severe lactic acidosis (blood pH 6.81, bicarbonate 4 mEq/L, lactate 25.7 mEq/L). Despite intravenous bicarbonate therapy, he decompensated and was placed on a combination of hemodialysis and charcoal hemoperfusion for a continuous time of 25 hours. His hospital course was complicated by acute renal failure requiring a period of intermittent hemodialysis. He has since made a complete recovery. The second case was a 53-year-old man who ingested 50 g of metformin. He also presented with severe lactic acidosis (blood pH 6.85, bicarbonate 3 mEq/L and lactate 28.4 mEq/L) and deteriorated despite intravenous bicarbonate therapy. He was placed on hemodialysis as a continuous therapy for 21 hours. His hospital course was complicated by acute renal failure requiring a period of intermittent hemodialysis. He has subsequently made a complete recovery. Metformin-associated lactic acidosis carries a high mortality rate. Prolonged hemodialysis should be considered as an early treatment option in these cases.