Reappraisal of the toxicology of ethylene glycol. IV. The metabolism of labelled glycollic and glyoxylic acids in the rhesus monkey

Final Report On the Safety Assessment of Glycolic Acid, Ammonium, Calcium, Potassium, and Sodium Glycolates, Methyl, Ethyl, Propyl, and Butyl Glycolates, and Lactic Acid, Ammonium, Calcium, Potassium, Sodium, and Tea-Lactates, Methyl, Ethyl, Isopropyl, and Butyl Lactates, and Lauryl, Myristyl, and Cetyl Lactates

This report provides a review of the safety of Glycolic Acid, Ammonium, Calcium, Potassium, and Sodium Glycolates, Methyl, Ethyl, Propyl, and Butyl Glycolates, Lactic Acid, Ammonium, Calcium, Potassium, Sodium, and TEA-Lactates, and Lauryl, Myristyl, and Cetyl Lactates. These ingredients belong to a group known as alpha-hydroxy acids (AHAs). Products containing these ingredients may be for consumer use, salon use, or medical use. This report does not address the medical use. In consumer and salon use, AHAs can function as mild exfoliants, but are also used as pH adjusters and skin-conditioning agents. AHAs are absorbed by the skin; the lower the pH, the greater the absorption. Metabolism and distribution studies show expected pathways and distribution. Consistent with these data, acute oral animal studies show oxalate-induced renal calculi, an increase in renal oxalate, and nephrotoxic effects. No systemic effects in animals were seen with dermal application, but irritation at the sight of application was produced. While many animal studies were performed to evaluate AHA-induced skin irritation, it was common for either the AHA concentration or the pH of the formulation to be omitted, limiting the usefulness of the data. Clinical testing using AHA formulations of known concentration and pH was done to address the issue of skin irritation as a function of concentration and pH. Skin irritation increased with AHA concentration at a given pH. Skin irritation increased when the pH of a given AHA concentration was lowered. Repeat insult patch tests using lotions and creams containing up to 10% Glycolic or Lactic Acid were negative. Glycolic Acid at concentrations up to 10% was not comedogenic and Lactic Acid at the same concentrations did not cause immediate urticarial reactions. Glycolic Acid was found to be nonirritating to minimally irritating in animal ocular tests, while Lactic Acid was found to be nonirritating to moderately irritating. In vitro testing to predict ocular irritation suggested Glycolic Acid would be a minimal to moderate-severe ocular irritant, and that Lactic Acid would be a minimal to moderate ocular irritant. Developmental and maternal toxicity were reported in rats dosed by gavage at the highest dose level used in a study that exposed the animals on days 7-21 of gestation. No developmental toxicity was reported at levels that were not maternally toxic. AHAs were almost uniformly negative in genotoxicity tests and were not carcinogenic in rabbits or rats. Clinical reports suggested that AHAs would enhance the penetration of hydroquinone and lidocaine. Animal and clinical tests were done to further evaluate the potential ofAHAs to enhance the skin penetration of other chemical agents. Pretreatment of guinea pig skin with Glycolic Acid did not affect the absorption of hydroquinone or musk xylol. Clinical tests results indicated no increase in penetration of hydrocortisone or glycerin with Glycolic Acid pretreatment. Because AHAs can act to remove a portion of the stratum corneum, concern was expressed about the potential that pretreatment with AHAs could increase skin damage produced by UV radiation. Clinical testing was done to determine the number of sunburn cells (cells damaged by UV radiation that show distinct morphologic changes) produced by 1 MED of UV radiation in skin pretreated with AHAs. A statistically significant increase in the number of sunburn cells was seen in skin pretreated with AHAs compared to controls. These increases, however, were less than those seen when the UV dose was increased from 1 MED to 1.56 MED. The increase in UV radiation damage associated with AHA pretreatment, therefore, was of such a magnitude that it is easily conceivable that aspects of product formulation could eliminate the effect. Based on the available information included in this report, the CIR Expert Panel concluded that Glycolic and Lactic Acid, their common salts and their simple esters, are safe for use in cosmetic products at concentrations ≤10%, at final formulation pH≥3.5, when formulated to avoid increasing sun sensitivity or when directions for use include the daily use of sun protection. These ingredients are safe for use in salon products at concentrations ≤30%, at final formulation pH ≥3.0, in products designed for brief, discontinuous use followed by thorough rinsing from the skin, when applied by trained professionals, and when application is accompanied by directions for the daily use of sun protection.

Ethylene glycol: an estimate of tolerable levels of exposure based on a review of animal and human data

Upon ingestion ethylene glycol (EG, monoethylene glycol) is rapidly absorbed from the gastrointestinal tract, and depending on the severity of exposure signs of toxicity may progress through three stages. Neurological effects characterize the first step consisting of central nervous depression (intoxication, lethargy, seizures, and coma). The second stage, usually 12-24 h after ingestion, is characterized by metabolic acidosis due to the accumulation of acidic metabolites of EG, primarily glycolic acid (GA), contributing to the ensuing osmolal and anion gaps. Stage 3, generally 24-72 h after ingestion, is determined mainly by oxalic acid excretion, nephropathy, and eventual renal failure. Because the toxicity of EG is mediated principally through its metabolites, adequate analytical methods are essential to provide the information necessary for diagnosis and therapeutic management. The severe metabolic acidosis and multiple organ failure caused by ingestion of high doses of EG is a medical emergency that usually requires immediate measures to support respiration, correct the electrolyte imbalance, and initiate hemodialysis. Since metabolic acidosis is not specific to EG, whenever EG intoxication is suspected, every effort should be made to determine EG as well as its major metabolite GA in plasma to confirm the diagnosis and to institute special treatment without delay. A number of specific and sensitive analytical methods (GC, GC-MS, or HPLC) are available for this purpose. Due to the rapid metabolism of EG, the plasma concentration of GA may be higher than that of EG already upon admission. As toxicity is largely a consequence of metabolism of EG to GA and oxalic acid, the simultaneous quantification of EG and GA is important. Formation of calcium oxalate monohydrate in the urine may be a useful indicator of developing oxalate nephrosis although urine crystals can result without renal injury. The pathways involved in the metabolism of EG are qualitatively similar in humans and laboratory animals, although quantitative differences have been reported. Comparison between species is difficult, however, because the information on humans is derived mainly from acute poisoning cases whereas the effects of repeated exposures have been investigated in animal experiments. Based on published data the minimum human lethal dose of EG has been estimated at approx. 100 ml for a 70-kg adult or 1.6 g/kg body weight (calculation of dose in ml/kg to mg/kg based in EG density=1.11 g/l). However, human data from case reports are generally insufficient for the determination of a clear dose-response relationship and quantification of threshold doses for systemic toxicity, in particular renal effects, is limited. As toxicity is largely a consequence of metabolism of EG to GA, it is important to note that no signs of renal injury have developed at initial plasma glycolate concentrations of up to 10.1 mM (76.7 mg/dl). Plasma EG levels of 3.2 mM (20 mg/dl) are considered the threshold of toxicity for systemic exposure, if therapeutic strategy is based on the EG concentration alone.

American Academy of Clinical Toxicology Practice Guidelines on the Treatment of Ethylene Glycol Poisoning. Ad Hoc Committee

Fomepizole (4-methylpyrazole, 4-MP, Antizol) is a potent inhibitor of alcohol dehydrogenase that was approved recently by the US Food and Drug Administration (FDA) for the treatment of ethylene glycol poisoning. Although ethanol is the traditional antidote for ethylene glycol poisoning, it has not been studied prospectively. Furthermore, the FDA has not approved the use of ethanol for this purpose. Case reports and a prospective case series indicate that the intravenous (i.v.) administration of fomepizole every 12 hours prevents renal damage and metabolic abnormalities associated with the conversion of ethylene glycol to toxic metabolites. Currently, there are insufficient data to define the relative role of fomepizole and ethanol in the treatment of ethylene glycol poisoning. Fomepizole has clear advantages over ethanol in terms of validated efficacy, predictable pharmacokinetics, ease of administration, and lack of adverse effects, whereas ethanol has clear advantages over fomepizole in terms of long-term clinical experience and acquisition cost. The overall comparative cost of medical treatment using each antidote requires further study.

Ethylene glycol antifreeze poisoning. Three case reports and a review of treatment

We present three patients with ethylene glycol antifreeze poisoning whose management included the use of continuous veno-venous haemodiafiltration. Results from these cases demonstrate clearance of the ethylene glycol molecule.

Determination of cyclic butylboronate esters of some 1,2- and 2,3-diols in plasma by high-resolution gas chromatography/mass spectrometry

A gas chromatographic/mass spectrometric analytical procedure is described to determine glycols in plasma as cyclic butyl boronate esters. The method, involving a pre-deproteinization step, required only 0.25 ml of plasma and a short time (20 min) to react with the derivatizing agent (butyl boronic acid). The gas chromatographic separation on a CP Sil 8 CB silica capillary column coupled to a mass detector assured a complete identification of the compounds. The analytical recoveries (greater than 95%) with low coefficient of variation (4-11%) assured the feasibility of the method over a concentration range from 5 to 1000 micrograms ml-1 for each glycol. The lower detection limits, namely 1-5 micrograms ml-1, confirmed the sensitivity of the method.

4-Methylpyrazole may be an alternative to ethanol therapy for ethylene glycol intoxication in man

4-Methylpyrazole (4 MP) is a strong inhibitor of alcohol dehydrogenase. Its use in acute ethylene glycol (EG) or methanol intoxication has been suggested in experimental studies about its efficacy and safety. We report three cases of accidental intoxication with ethylene glycol in man treated orally with 20 mg/kg/day of 4 MP. The treatment was maintained until plasma EG concentrations became unmeasurable. The patients were admitted early during the course of the poisoning. Their neurological status was good. A slight metabolic acidosis observed in two cases was easily corrected and did not recur. Renal function remained normal in all cases. No patient underwent hemodialysis. On admission plasma EG concentrations were 24.2 mmol/l, 13 mmol/l and 9.7 mmol/l respectively. Plasma EG half-lives were 14.5, 11.5 and 14.75 hours respectively. Plasma oxalate concentrations and the rate of urine oxalate elimination, determined in two patients, were high on admission but quickly returned to normal. Concerning possible side effects of 4 MP, a skin rash was observed in one patient and a possible eosinophilia in the others. These three cases suggest that 4 MP may decrease the metabolic consequences of EG poisoning in man and may be of therapeutic value when administered early during the course of the intoxication before coma, seizures and organic renal failure have occurred.

Independent plasma levels of sodium and glycine during transurethral resection of the prostate

This study was done to evaluate the potential role of plasma glycine levels as an indicator of the biochemical changes occurring during or shortly after transurethral resection of the prostate ( TURP ). Seventeen patients undergoing TURP were studied to determine the fate of the absorbed glycine and its effects on other amino acids and their relationship to changes in serum sodium and osmolarity. Twelve patients showed more than 100 per cent increase in plasma glycine levels with values ranging to more than 100-fold elevation. Only two patients showed a change in serum sodium of greater than 10 mEq/l with corresponding change in osmolarity. In one such patient there was no accompanying change in plasma glycine. Thus, major changes in plasma glycine and serum sodium may occur independently of one another, and may separately account for manifestations of the reactions following TURP .

Efficacy and toxicity of the solvent polyethylene glycol 400 in monkey model

Several antiepileptic drugs, such as carbamazepine and clonazepam, have low bioavailability in solid form and are insoluble in an aqueous solution. Alcohol solvents are often employed as vehicles when these drugs are studied in animal models. Secondary and particularly tertiary alcohols are suspected of some anticonvulsant activity. The present research evaluated the possibility that polyethylene glycol 400 (PEG 400) might be efficacious, toxic, or both. Monkeys (N = 11) rendered epileptic by aluminum-hydroxide were administered PEG 400 by constant rate (1 ml/hr) intravenous infusion for 3--4 weeks, preceded and followed by several weeks of baseline. At a concentration of 60%, PEG 400 significantly reduced seizure frequency, but also exhibited severe side effects. These findings suggest that experimental testing of anticonvulsants may be compromised when this or similar solvents are used chronically.

Ethylene and diethylene glycol toxicity

1. Blood concentrations of ethylene and diethylene glycol were evaluated in Sprague-Dawley rats at varying intervals following oral dosages of the glycols. 2. Ethylene and diethylene glycol in rat blood stored under refrigeration at 4 degrees +/- 10 degrees C for a period of 30 days exhibited minimal concentration losses, contrary to previous reports. 3. The amount of oxalate in the blood and kidneys of Sprague-Dawley rats doses with ethylene and diethylene glycol was quantitated. The animals dosed with ethylene glycol demonstrated significantly higher oxalate levels, particularly at 8 hr post-dosing, than similar animals dosed with diethylene glycol. 4. Ethylene glycol induced oxalate deposition within the kidney without significant histologic changes. Diethylene glycol induced histologic changes within the kidneys without kidney oxalate deposition. 5. Maximal kidney oxalate levels, following ethylene glycol dosage, occurred concurrently with peak blood oxalate concentrations. In the case of diethylene glycol, kidney oxalate levels did not peak until 4 hr after maximal blood oxalate levels. 6. Ethylene and diethylene glycol induced different modes of death in Sprague-Dawley rats.