Acute methanol toxicity in minipigs

Effects of crude glycerin from waste vegetable oil supplementation on feed intake, ruminal fermentation characteristics, and nitrogen utilization of goats

This experiment was evaluation of the effects of increasing concentrations of crude glycerin from waste vegetable oil (CGWVO) in diets on feed intake, digestibility, ruminal fermentation characteristics, and nitrogen balance of goats. Four crossbred male (Thai Native × Anglo Nubian) goats, with an average initial body weight (BW) of 31.5 ± 1.90 kg, were randomly assigned according to a 4 × 4 Latin square design. The dietary treatments contained 0, 2, 4, and 6 % of dietary dry matter (DM) of CGWVO. Based on this experiment, there were significantly different (P > 0.05) among treatment groups regarding DM intake and digestion coefficients of nutrients (DM, OM, CP, EE, NDF, and ADF), which goats receiving 6 % of CGWVO had lower daily DMI and nutrient intake than those fed on 0, 2, and 4 % of CGWVO. Ruminal pH, NH3-N, and blood urea nitrogen (BUN) concentration were unchanged by dietary treatments, except that for 6 % of CGWVO supplementation, NH3-N, and BUN were lower (P < 0.05) than for the diets 0 % of CGWVO, while the differences between the diets 0, 2, and 4 % of CGWVO were not significant. The amounts of N absorption and retention were similar among treatments, except that for 6 % of CGWVO which N absorption was lower (P < 0.05) than among treatments while the difference between the diets 0, 2, and 4 % of CGWVO were not significant. Based on this study, CGWVO levels up to 4 % in total mixed ration could be efficiently utilized for goats. This study was a good approach in exploiting the use of biodiesel production from waste vegetable oil for goat production.

A chemical analysis of samples of crude glycerol from the production of biodiesel in Australia, and the effects of feeding crude glycerol to growing-finishing pigs on performance, plasma metabolites and meat quality at slaughter

The aims of this study were to: (i) determine the chemical composition of 11 samples of crude glycerol collected from seven Australian biodiesel manufacturers; and (ii) examine the effects of increasing levels of crude glycerol fed to growing-finishing pigs on performance, plasma metabolites and meat quality at slaughter. Chemical composition of crude glycerol samples varied considerably; glycerol content ranged between 38 and 96%, with some samples containing up to 29% ash and 14% methanol. One of these samples (76.1% glycerol, 1.83% methanol) was then fed to 64 female pigs (50.9 ± 5.55 kg; mean ± s.d.) allocated to one of five dietary treatments (0, 4, 8, 12 and 16% crude glycerol) until they reached 105 kg liveweight. There were no statistical differences in performance indices with increasing levels of added glycerol, although there was an unexpectedly high variation between treatments. Blood glycerol levels were unaffected by diet in week two of the experiment, but increased linearly (P < 0.001) with increasing levels of dietary glycerol before slaughter. The inclusion of crude glycerol did not influence any meat quality parameters at slaughter (P > 0.05). Diets containing added crude glycerol were less dusty after mixing, but diets that contained 8, 12 and 16% glycerol all formed a firm aggregate within 24 h of mixing that presented some feeding difficulties. This might restrict inclusion of glycerol in mash diets to dietary levels less than 8%. Furthermore, levels of residues such as methanol and ash should be monitored to prevent excessive amounts of these compounds in pig diets.

Formate pharmacokinetics during formate administration in folate-deficient young swine

The objective of the study was to investigate the effect of folate deficiency on formate pharmacokinetics during formate administration in folate-deficient young swine. Methanol is a one of the congeners found in alcoholic beverages. Methanol toxicity is mediated through formic acid and thus plays a significant role in the pathophysiology of alcoholism. Folate is a required cofactor in the metabolism of formate to CO(2) and H(2)O. We investigate the effect of folate deficiency on the pharmacokinetics of formate. Twelve young pigs were pair-matched and randomly placed into 2 groups on acquisition ( approximately 5 weeks). One group was made folate deficient (FFD) by feeding with a folic acid-deficient diet; the other group (FFC) was fed a diet supplemented with folate. Four animals (31-38 kg) from each group were infused (intravenous) with 351 mg/kg of sodium formate. The remaining 2 animals were infused with isotonic sodium chloride solution. Blood samples were collected before and at 10, 20, 30, 45, 60, 90, 120, 180, 240, and 480 minutes post dose and analyzed for formate levels by gas chromatography. Pharmacokinetic parameters were estimated using a noncompartmental approach. Formate (mean +/- SE) accumulation was higher in the FFD group than the FFC group (AUC(0-infinity) of 72.37 +/- 8.29 vs 30.08 +/- 2.58 g min/L, respectively). Elimination was also slower in the FFD group (FFD systemic clearance = 0.12 +/- 0.01 L/min compared with FFC systemic clearance = 0.27 +/- 0.02 L/min). Half-life of elimination was 2.5 times longer in FFD group (113 +/- 1 minute) than in FFC group (45 +/- 6 minutes). Folate deficiency had no influence on the volume of distribution of formate (18.84 +/- 1.05 L in FFD vs 17.21 +/- 1.35 L in FFC). Adequate folate status is important in the elimination of formate. A folate-deficiency state results in a reduction in formate elimination kinetics, which may increase the risk of formate toxicity.

Simultaneous determination of formate and acetate in whole blood and urine from humans using gas chromatography–mass spectrometry

We devised a sensitive and simple method for simultaneous determination of formate and acetate in whole blood and urine from humans using gas chromatography-mass spectrometry. Formate and acetate were alkylated with pentafluorobenzyl bromide in the mixture of acetone and phosphate buffer (pH 6.8). The derivatives obtained were analyzed using gas chromatography-mass spectrometry in positive-ion electron ionization (EI) mode. The lower limit of detection for both compounds was 0.02mM. The calibration curves for formate and acetate were linear over the concentration range from 0.05 to 5.0mM. Accuracy and precision of the method were evaluated and the coefficients of variation were within 10%. With use of this method, levels of formate and acetate in whole blood can be determined in forensic cases.

NTP-CERHR Expert Panel report on the reproductive and developmental toxicity of methanol

The National Toxicology Program (NTP) and the National Institute of Environmental Health Sciences (NIEHS) established the NTP Center for the Evaluation of Risks to Human Reproduction (CERHR) in June 1998. The purpose of the Center is to provide timely, unbiased, scientifically sound evaluations of human and experimental evidence for adverse effects on reproduction, including development, caused by agents to which humans may be exposed. Methanol was selected for evaluation by the CERHR based on high production volume, extent of human exposure, and published evidence of reproductive or developmental toxicity. Methanol is used in chemical syntheses and as an industrial solvent. It is a natural component of the human diet and is found in consumer products such as paints, antifreeze, cleaning solutions, and adhesives. It is used in race car fuels and there is potential for expanded use as an automobile fuel. This evaluation is the result of a 10-month effort by a 12-member panel of government and non-government scientists that culminated in a public Expert Panel meeting. This report has been reviewed by CERHR staff scientists, and by members of the Methanol Expert Panel. Copies have been provided to the CERHR Core Committee, which is made up of representatives of NTP-participating agencies. This report is a product of the Expert Panel and is intended to (1). interpret the strength of scientific evidence that a given exposure or exposure circumstance may pose a hazard to reproduction and the health and welfare of children; (2). provide objective and scientifically thorough assessments of the scientific evidence that adverse reproductive/development health effects are associated with exposure to specific chemicals or classes of chemicals, including descriptions of any uncertainties that would diminish confidence in assessment of risks; and (3). identify knowledge gaps to help establish research and testing priorities. The expert panel report becomes a central part of the subsequent NTP-CERHR Monograph. Each monograph includes the NTP Brief on the chemical under evaluation, the expert panel report, and all public comments on the expert panel report. The NTP Brief contains the NTP's conclusions on the potential for exposure to result in adverse effects on human development and reproduction. It is based on the expert panel report, public comments on the report, and relevant data published after the expert panel report was completed. NTP-CERHR Monographs are publicly available and are transmitted to appropriate health and regulatory agencies.

American Academy of Clinical Toxicology practice guidelines on the treatment of methanol poisoning

EPIDEMIOLOGY

Almost all cases of acute methanol toxicity result from ingestion, though rarely cases of poisoning have followed inhalation or dermal absorption. The absorption of methanol following oral administration is rapid and peak methanol concentrations occur within 30-60minutes.

MECHANISMS OF TOXICITY

Methanol has a relatively low toxicity and metabolism is responsible for the transformation of methanol to its toxic metabolites. Methanol is oxidized by alcohol dehydrogenase to formaldehyde. The oxidation of formaldehyde to formic acid is facilitated by formaldehyde dehydrogenase. Formic acid is converted by 10-formyl tetrahydrofolate synthetase to carbon dioxide and water. In cases of methanol poisoning, formic acid accumulates and there is a direct correlation between the formic acid concentration and increased morbidity and mortality. The acidosis observed in methanol poisoning appears to be caused directly or indirectly by formic acid production. Formic acid has also been shown to inhibit cytochrome oxidase and is the prime cause of ocular toxicity, though acidosis can increase toxicity further by enabling greater diffusion of formic acid into cells.

FEATURES

Methanol poisoning typically induces nausea, vomiting, abdominal pain, and mild central nervous system depression. There is then a latent period lasting approximately 12-24 hours, depending, in part, on the methanol dose ingested, following which an uncompensated metabolic acidosis develops and visualfunction becomes impaired, ranging from blurred vision and altered visual fields to complete blindness.

MANAGEMENT

For the patient presenting with ophthalmologic abnormalities or significant acidosis, the acidosis should be corrected with intravenous sodium bicarbonate, the further generation of toxic metabolite should be blocked by the administration of fomepizole or ethanol and formic acid metabolism should be enhanced by the administration of intravenous folinic acid. Hemodialysis may also be required to correct severe metabolic abnormalities and to enhance methanol and formate elimination. For the methanol poisoned patient without evidence of clinical toxicity, the first priority is to inhibit methanol metabolism with intravenous ethanol orfomepizole. Although there are no clinical outcome data confirming the superiority of either of these antidotes over the other, there are significant disadvantages associated with ethanol. These include complex dosing, difficulties with maintaining therapeutic concentrations, the need for more comprehensive clinical and laboratory monitoring, and more adverse effects. Thus fomepizole is very attractive, however, it has a relatively high acquisition cost.

CONCLUSION

The management of methanol poisoning includes standard supportive care, the correction of metabolic acidosis, the administration of folinic acid, the provision of an antidote to inhibit the metabolism of methanol to formate, and selective hemodialysis to correct severe metabolic abnormalities and to enhance methanol and formate elimination. Although both ethanol and fomepizole are effective, fomepizole is the preferred antidote for methanol poisoning.