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Concept: Phenformin


Hyperglycemia during corticosteroid and asparaginase therapy for acute lymphoblastic leukemia is a significant side effect that is usually treated with insulin. Metformin is an oral antidiabetic biguanide that may cause metabolic acidosis and liver enzyme abnormalities of possible concern in patients receiving chemotherapy.

Concepts: Anti-diabetic drug, Buformin, Glycogen, Phenformin, Diabetes mellitus, Anti-diabetic drugs, Metformin, Acute lymphoblastic leukemia


Abstract 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.

Concepts: Diabetes mellitus type 2, Suicide, Insulin, Diabetes mellitus, Lactic acidosis, Metformin, Anti-diabetic drug, Phenformin


Metformin (N,N-dimethylbiguanide), buformin (1-butylbiguanide) and phenformin (1-phenethylbiguanide) are anti-diabetic biguanide drugs, expected to having anti-cancer effect. The mechanism of anti-cancer effect by these drugs is not completely understood. In this study, we demonstrated that these drugs dramatically enhanced oxidative DNA damage under oxidative condition. Metformin, buformin and phenformin enhanced generation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in isolated DNA reacted with hydrogen peroxide (H2O2) and Cu(II), although these drugs did not form 8-oxodG in the absence of H2O2 or Cu(II). An electron paramagnetic resonance (EPR) study, utilizing alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone and 3,3,5,5-tetramethyl-1-pyrroline-N-oxide as spin trapping agents, showed that nitrogen-centered radicals were generated from biguanides in the presence of Cu(II) and H2O2, and that these radicals were decreased by the addition of DNA. These results suggest that biguanides enhance Cu(II)/H2O2 -mediated 8-oxodG generation via nitrogen-centered radical formation. The enhancing effect on oxidative DNA damage may play a role on anti-cancer activity.

Concepts: Buformin, Oxidative stress, Hydrogen peroxide, Anti-diabetic drug, Oxygen, Phenformin, Biguanide, Metformin


The biguanides are a family of drugs with diverse clinical applications. Metformin, a widely used anti-hyperglycemic biguanide, suppresses mitochondrial respiration by inhibiting respiratory complex I. Phenformin, a related anti-hyperglycemic biguanide, also inhibits respiration, but proguanil, which is widely used for the prevention of malaria, does not. The molecular structures of phenformin and proguanil are closely related and both inhibit isolated complex I. Proguanil does not inhibit respiration in cells and mitochondria because it is unable to access complex I. The molecular features that determine which biguanides accumulate in mitochondria, enabling them to inhibit complex I in vivo, are not known.

Concepts: Atovaquone, Inhibitor, Oxygen, Guanidines, Biguanide, Phenformin, Metformin, Cellular respiration


During the last decade, the burst of interest is observed to antidiabetic biguanide metformin as candidate drug for cancer chemoprevention. The analysis of the available data have shown that the efficacy of cancer preventive effect of metformin (MF) and another biguanides, buformin (BF) and phenformin (PF), has been studied in relation to total tumor incidence and to 17 target organs, in 21 various strains of mice, 4 strains of rats and 1 strain of hamsters (inbred, outbred, transgenic, mutant), spontaneous (non- exposed to any carcinogenic agent) or induced by 16 chemical carcinogens of different classes (polycycIic aromatic hydrocarbons, nitroso compounds, estrogen, etc.), direct or indirect (need metabolic transformation into proximal carcinogen), by total body X-rays and γ- irradiation, viruses, genetic modifications or special high fat diet, using one stage and two-stage protocols of carcinogenesis, 5 routes of the administration of antidiabetic biguanides (oral gavage, intraperitoneal or subcutaneous injections, with drinking water or with diet) in a wide ranks of doses and treatment regimens. In the majority of cases (86%) the treatment with biguanides leads to inhibition of carcinogenesis. In 14% of the cases inhibitory effect of the drugs was not observed. Very important that there was no any case of stimulation of carcinogenesis by antidiabetic biguanides. It was conclude that there is sufficient experimental evidence of anti-carcinogenic effect of antidiabetic biguanides.

Concepts: Biguanide, Phenformin, Nitrosamine, Metformin, Cancer, Oncology, Carcinogen, Benzene


A new salting-out assisted liquid-liquid extraction (SALLE) sample preparation method for the determination of the polar anti-diabetic biguanide drugs (metformin, buformin and phenformin) in blood plasma, urine and lake water samples were developed. The SALLE was performed by mixing samples (plasma (0.2mL), urine or lake water (1.0mL)) with acetonitrile (0.4mL for plasma, 0.5mL for urine or lake water), sodium hydroxide powder was then added for the phase separation. The effects of type of salting-out reagent, type of extraction solvent, volumes of acetonitrile and sample, amount of sodium hydroxide, vortexing and centrifugation times on the extraction efficiency were investigated. The upper layer, containing the biguanides, was directly injected into a HPLC unit using ZIC-HILIC column (150mm×2.1mm×3.5μm) and was detected at 236nm. The method was validated and calibration curves were linear with r2>0.99 over the range of 20-2000μgL-1 for plasma and 5-2000μgL-1 for urine and lake water samples. The limits of detection were in the range (3.8-5.6)μgL-1, (0.8-1.5)μgL-1 and (0.3-0.8)μgL-1 for plasma, urine and lake water, respectively. The accuracies in the three matrices were within 87.3-103%, 87.4-109%, 82.2-109% of the nominal concentration for metformin, buformin and phenformin, respectively. The relative standard deviation for inter- and intra -day precision were in the range of 1.0-17% for all analytes in the three matrices.

Concepts: Ethanol, Buformin, Sodium hydroxide, Anti-diabetic drug, Sodium, Phenformin, Metformin, Biguanide


Metformin remains a widely-used, first-line pharmacotherapy agent for patients with type 2 diabetes mellitus because of its efficacy, mild side effects, and affordability.However, use of this medication has traditionally been shunned by clinicians in patient populations that are considered at risk of lactic acidosis, such as those with heart failure. The underutilization of metformin can largely be attributed to the historical stigma of its biguanide predecessor, phenformin, and its association with lactic acidosis. Despite various studies finding low rates of lactic acidosis and the United States Federal Drug Administration’s subsequent removal of heart failure from metformin’s contraindication labeling in 2006, this oral hypoglycemic remains underutilized in this patient population. In addition to reports of the safe use of metformin in the heart failure population, a multitude of studies have also additionally suggested a modest reduction in mortality and morbidity. Metformin’s role should be strongly reconsidered in the armamentarium of diabetes management in heart failure patients.

Concepts: Lactic acidosis, Anti-diabetic drug, Sulfonylurea, Phenformin, Obesity, Diabetes mellitus type 2, Diabetes mellitus, Metformin


The anti-diabetic biguanide drugs metformin (METF) and phenformin (PHEN) may have anti-cancer effects. Biguanides suppress plasma growth factors, but nonetheless, the view that these mitochondrial inhibitors accumulate in tumor tissue to an extent that leads to severe energetic stress or alleviation of hypoxia-induced radioresistance is gaining ground. Our cell studies confirm that biguanides inhibits cell proliferation by targeting respiration, but only at highly suprapharmacological concentrations due to low drug retention. Biodistribution/PET studies of (11)C-labeled metformin ((11)C-METF) revealed that plasma bioavailability remained well below concentrations with metabolic/anti-proliferative in vitro effects, following a high oral dose. Intraperitoneal administration resulted in higher drug concentrations, which affected metabolism in normal organs with high METF uptake (e.g., kidneys), but tumor drug retention peaked at low levels comparable to plasma levels and hypoxia was unaffected. Prolonged intraperitoneal treatment reduced tumor growth in two tumor models, however, the response did not reflect in vitro drug sensitivity, and tumor metabolism and hypoxia was unaffected. Our results do not support that direct inhibition of tumor cell respiration is responsible for reduced tumor growth, but future studies using (11)C-METF-PET are warranted, preferably in neoplasia’s originating from tissue with high drug transport capacity, to investigate the controversial idea of direct targeting.

Concepts: Oxygen, Biguanide, Phenformin, Mitochondrion, Carbon dioxide, Enzyme inhibitor, Adenosine triphosphate, Cellular respiration


We developed and validated a liquid chromatography tandem mass spectrometry (LC-MS/MS) method to detect and quantitate 14 anti-diabetic, 2 anti-obesity and 3 cholesterol-lowering drugs in botanical dietary supplements marketed for blood sugar management. Many botanical dietary supplements which carry label statements related to blood sugar management are available over the internet. Potential adulteration of such dietary supplements with anti-diabetic and other prescription drugs, some of which have been removed from the market due to adverse events, is of concern. No significant matrix effects were observed and mean recoveries of all 19 analytes from a single product matrix were 88 to 113% at spiking concentrations from 500 to 2000 μg/g. Mean recoveries of metformin, phenformin, and sibutramine from matrices prepared from multiple product composites ranged from 93 to 115% at a spiking concentration of 100 μg/g. The relative standard deviations (RSD) (%) of intra-day analyses ranged from 0.2 to 13 for all recovery studies. Eighty dietary supplements obtained in the U.S. and carrying label statements related to blood sugar management were analyzed using this method and none were found to be adulterated with the above 19 drugs. Two products obtained outside of the U.S. and known to be adulterated were also analyzed by this method and found to contain phenformin, glibenclamide, and sibutramine. This method provided satisfactory selectivity, linearity, accuracy, precision, and sensitivity for rapid determination of 19 drugs and has broad applicability for the analysis of dietary supplements for possible adulteration with these compounds.

Concepts: Phenformin, Mass spectrometry, Adulterant, Standard deviation, Anti-diabetic drug, Metformin


Metformin is the most commonly prescribed treatment for Type II diabetes and related disorders, however molecular insights into its mode(s) of action have been limited by an absence of structural data. Structural considerations along with an increasing body of literature demonstrating its effects on one-carbon metabolism suggest the possibility of folate mimicry and anti-folate activity. Motivated by increasing recognition that anti-diabetic biguanides may act directly upon the gut microbiome, we have determined structures of the complexes formed between the anti-diabetic biguanides: phenformin, buformin, and metformin and E. coli dihydrofolate reductase (ecDHFR) based on NMR, crystallographic and molecular modeling studies. Inter-ligand Overhauser effects indicate that metformin can form ternary complexes with p-aminobenzoyl-L-glutamate (pABG) as well as other ligands that occupy the region of the folate binding site that interacts with pABG, however DHFR inhibition is not cooperative. The biguanides inhibit the activity of ecDHFR competitively, with Ki ~ 20 mM (metformin) or 0.2 mM (phenformin). This inhibition may be significant at concentrations present in the gut of treated individuals, and inhibition of intestinal mucosal cells may also occur if accumulated levels are sufficient. Perturbation of folate homeostasis can alter the pyridine nucleotide redox ratios that regulate cellular metabolism.

Concepts: Anti-diabetic drug, Dihydrofolic acid, Metabolism, Phenformin, Enzyme, Biguanide, Diabetes mellitus type 2, Metformin