The fate of the ethanol analogue 1,3-butanediol in the dog. An in vivo-in vitro comparison

In view of the current interest in 1,3-butanediol as food additive or potential drug its pharmacokinetics have been investigated in the dog and compared to its oxidation in vitro by alcohol dehydrogenase. Plasma disappearance of i.v. doses of 5.5 mmol/kg were zero order followed by first order. Assuming Michaelis-Menten kinetics a V_max of 1.23 ± S.D. 0.27 μmol/min/g of liver and a K_m of 1.15 ± 0.85 mM could be calculated. The corresponding values for 1,3-butanediol metabolism by alcohol dehydrogenase in vitro were 1.62 ± 0.34 μmol/min/g of liver and 5.11 ± 1.45 mM. Hepatic vein catheterizations were used to measure hepatic blood flow (18.1 ± 2.8 ml/min/kg) and the fraction of butanediol disappearing in the liver, which was only 34.2 ± 6.6 per cent. Compared to ethanol, V_max of 1,3-butanediol was 15 per cent smaller in vitro, 45 per cent smaller in vivo, K_m was 3 times larger in vitro and 60 per cent smaller in vivo. The splanchnic elimination fraction of 1,3-butanediol was about $\text{1}\text{2}$ the one of ethanol. These data are consistent with the concept, that oxidation by alcohol dehydrogenase is the major route of butanediol elimination. The differences between 1,3-butanediol and ethanol metabolism, however, render different pharmacological and toxicological effects likely.     

Current management of ethylene glycol poisoning.

Ethylene glycol, a common antifreeze, coolant and industrial solvent, is responsible for many instances of accidental and intentional poisoning annually. Following ingestion, ethylene glycol is first hepatically metabolised to glycoaldehyde by alcohol dehydrogenase. Glycoaldehyde is then oxidised to glycolic acid, glyoxylic acid and finally oxalic acid. While ethylene glycol itself causes intoxication, the accumulation of toxic metabolites is responsible for the potentially fatal acidosis and renal failure, which characterises ethylene glycol poisoning. Treatment of ethylene glycol poisoning consists of emergent stabilisation, correction of metabolic acidosis, inhibition of further metabolism and enhancing elimination of both unmetabolised parent compound and its metabolites. The prevention of ethylene glycol metabolism is accomplished by the use of antidotes that inhibit alcohol dehydrogenase. Historically, this has been done with intoxicating doses of ethanol. At a sufficiently high concentration, ethanol saturates alcohol dehydrogenase, preventing it from acting on ethylene glycol, thus allowing the latter to be excreted unchanged by the kidneys. However, ethanol therapy is complicated by its own inherent toxicity, and the need to carefully monitor serum ethanol concentrations and adjust the rate of administration. A recent alternative to ethanol therapy is fomepizole, or 4-methylpyrazole. Like ethanol, fomepizole inhibits alcohol dehydrogenase; however it does so without producing serious adverse effects. Unlike ethanol, fomepizole is metabolised in a predictable manner, allowing for the use of a standard, validated administration regimen. Fomepizole therapy eliminates the need for the haemodialysis that is required in selected patients who are non-acidotic and have adequate renal function.     

Determination of glycols in biological specimens by gas chromatography-mass spectrometry

A simple extraction and derivatization procedure for the analysis of eight glycols (ethylene glycol, EG; diethylene glycol, DEG; triethylene glycol, TEG; 1,2-propanediol, 1,2-PD; 1,3-propanediol, 1,3-PD; 1,2-butanediol, 1,2-BD; 2,3-butanediol, 2,3-BD; and hexylene glycol, HXG) using a 2-microL serum or blood sample is described. Following deproteinisation with acetonitrile, derivatization to its mono or di TMS derivative, glycols were detected using gas chromatography-electron impact mass spectrometry equipped with a split-spitless inlet and a DB-5MS column in the scan mode from 40 to 500 amu. Gamma-hydroxybutyrate-d6 (GHB-d6) was used as the internal standard. The limits of detection and quantitation in 2 pL of serum ranged, respectively, from 0.7 mg/L for EG to 8.5 mg/L for TEG and from 1.3 mg/L for EG to 18.2 mg/L for 1,2-PD. A linear response was observed over the concentration range from 1 to 800 mg/L for EG and 18 from 800 for TEG and 1,2-PD for serum and blood. Coefficients of variation for both intra-assay precision and interassay reproductibility ranged respectively between 1.9% for TEG to 4.9% for 1,2-PD (11.8% for HXG) and 3.5% for DEG to 9% for 2,3-BD (20.4 for HXG) at the 400 mg/L serum level. The method was applied to plasma and whole blood.     

Cutaneous metabolism of glycol ethers

The toxicity of glycol ethers is associated with their oxidation to the corresponding aldehyde and alkoxyacetic acid by cytosolic alcohol dehydrogenase (ADH; EC 1.1.1.1.) and aldehyde dehydrogenase (ALDH; 1.2.1.3). Dermal exposure to these compounds can result in localised or systemic toxicity including skin sensitisation and irritancy, reproductive, developmental and haemotological effects. It has previously been shown that skin has the capacity for local metabolism of applied chemicals. Therefore, there is a requirement to consider metabolism during dermal absorption of these compounds in risk assessment for humans. Cytosolic fractions were prepared from rat liver, and whole and dermatomed skin by differential centrifugation. Rat skin cytosolic fractions were also prepared following multiple dermal exposure to dexamethasone, ethanol or 2-butoxyethanol (2-BE). The rate of ethanol, 2-ethoxyethanol (2-EE), ethylene glycol, 2-phenoxyethanol (2-PE) and 2-BE conversion to alkoxyacetic acid by ADH/ALDH in these fractions was continuously monitored by UV spectrophotometry via the conversion of NAD⁺ to NADH at 340 nm. Rates of ADH oxidation by rat liver cytosol were greatest for ethanol followed by 2-EE >ethylene glycol >2-PE >2-BE. However, the order of metabolism changed to 2-BE >2-PE >ethylene glycol >2-EE >ethanol using whole and dermatomed rat skin cytosolic fractions, with approximately twice the specific activity in dermatomed skin cytosol relative to whole rat skin. This suggests that ADH and ALDH are localised in the epidermis that constitutes more of the protein in dermatomed skin than whole skin cytosol. Inhibition of ADH oxidation in rat liver cytosol by pyrazole was greatest for ethanol followed by 2-EE >ethylene glycol >2-PE >2-BE, but it only inhibited ethanol metabolism by 40% in skin cytosol. Disulfiram completely inhibited alcohol and glycol ether metabolism in the liver and skin cytosolic fractions. Although ADH1, ADH2 and ADH3 are expressed at the protein level in rat liver, only ADH1 and ADH2 are selectively inhibited by pyrazole and they constitute the predominant isoforms that metabolise short-chain alcohols in preference to intermediate chain-length alcohols. However, ADH1, ADH3 and ADH4 predominate in rat skin, demonstrate different sensitivities to pyrazole, and are responsible for metabolising glycol ethers. ALDH1 is the predominant isoform in rat liver and skin cytosolic fractions that is selectively inhibited by disulfiram and responds to the amount of aldehyde formed by the ADH isoforms expressed in these tissues. Thus, the different affinity of ADH and ALDH for alcohols and glycol ethers of different carbon-chain length may reflect the relative isoform expression in rat liver and skin. Following multiple topical exposure, ethanol metabolism increased the most following ethanol treatment, and 2-BE metabolism increased the most following 2-BE treatment. Ethanol and 2-BE may induce specific ADH and ALDH isoforms that preferentially metabolise short-chain alcohols (i.e. ADH1, ALDH1) and longer chain alcohols (i.e. ADH3, ADH4, ALDH1), respectively. Treatment with a general inducing agent such as dexamethasone enhanced ethanol and 2-BE metabolism suggesting induction of multiple ADH isoforms.     

Triethylene glycol poisoning treated with intravenous ethanol infusion

INTRODUCTION: Poisoning with triethylene glycol has been rarely reported in humans. Triethylene glycol is thought to be metabolized by alcohol dehydrogenase to acidic products resulting in the production of a metabolic acidemia. Triethylene glycol metabolism has previously been shown to be inhibited by fomepizole (4-methyl pyrazole) administration. We report a case of triethylene glycol ingestion, presenting with a metabolic acidemia, treated with intravenous ethanol administration. CASE REPORT: A 23-year-old female presented to the emergency department approximately 1-1.5 hours following ingestion of a gulp of triethylene glycol (99%) brake fluid with coma (GCS-3) and metabolic acidemia (pH 7.03, PCO2 44 mm Hg, Bicarbonate 11 mmol/L, anion gap 30 mmol/L, serum creatinine 90 mumol/L). She was intubated and given 100 mmol of intravenous sodium bicarbonate. An ethanol loading dose was administered followed by an infusion to maintain serum ethanol at 100 mg/dL. Acidemia gradually resolved over the next 8 hours and she was extubated 12 hours later. The ethanol infusion was continued for a total of 22 hours. There was no recurrence of acidemia. Serum ethanol, ethylene glycol, and methanol levels were nondetectable on presentation, as was serum salicylate. Urine drug of abuse screen and thin-layer chromatography revealed no other coingested substances. The patient was discharged to a psychiatric ward 36 hours postingestion. CONCLUSION: Pure triethylene glycol poisoning results in coma and metabolic acidemia and may be treated with alcohol dehydrogenase inhibitors such as ethanol.     

Inhibition of liver alcohol dehydrogenase and ethanol metabolism by 3-substituted thiolane 1-oxides

3-Substituted thiolane 1-oxides (methyl, n-butyl, n-hexyl, and phenyl) were prepared and tested as inhibitors of horse, monkey, and rat liver alcohol dehydrogenases and of ethanol metabolism in rats. These compounds inhibit alcohol oxidation in an uncompetitive manner with respect to ethanol as a varied substrate. Lengthening the alkyl substituent increased the inhibitory potency because of tighter binding in the hydrophobic substrate binding pocket of the alcohol dehydrogenases. Thus, the 3-hexyl derivative was the most potent inhibitor of the purified rat liver alcohol dehydrogenase, with a Kii value of 0.13 microM. The 3-butyl derivative was the best inhibitor of ethanol metabolism in rats, with a Kii value of 11 mumol/kg. The acute toxicity in mice of the butyl derivative was 1.4 mmol/kg. Since high concentrations of alcohol do not prevent the inhibitory effects of these compounds, they may be particularly useful for preventing poisoning by methanol or ethylene glycol.     

Acute propylene glycol ingestion

BACKGROUND: We describe a case of acute propylene glycol toxicity following ingestion of ethanol and propylene glycol-containing antifreeze in which blood lactate, serum propylene glycol, ethanol, and CO2 concentrations were serially measured. CASE REPORT: A 61-year-old man was hospitalized after acute ingestion of ethanol and automotive antifreeze. His clinical presentation and course were essentially unremarkable. Initial lab tests revealed serum ethanol concentration, 167 mg/dL, normal serum electrolytes and osmol gap, 120 mOsm/kg. Intravenous 10% ethanol infusion was begun for suspected ethylene glycol toxicity and discontinued at approximately 17 hours post-ingestion. Toxicological analysis of urine was positive for ethanol and propylene glycol, and negative for ethylene glycol, methanol, and isopropanol. Blood lactate was mildly elevated and serum CO2 concentration was normal. Gas chromatographic analysis of serial serum specimens for propylene glycol concentration revealed a maximum value of 470 mg/dL at 7 hours and a nonlinear decline to below detection limit (3 mg/dL) at 57 hours after antifreeze ingestion. The patient was discharged on hospital day 2. CONCLUSION: The propylene glycol elimination pattern, absence of significant acid-base disturbance, and minimal lactate elevation in this case are consistent with ethanol-related inhibition of propylene glycol metabolism. The effect of ethanol on clinical outcome after acute propylene glycol intoxication remains uncertain.     

A gas-liquid chromatographic method for quantitation of 1,3-butylene glycol in whole blood or plasma and the separation of the short chain glycols

A microanalytical method with direct on-column specimen injection for determination of 1,3-butylene glycol (1,3-butanediol) in whole blood or plasma using gas-liquid chromatography with flame ionization is described. Whole blood or serum (minimum of 10 microL) was mixed with an equal volume of internal standard (1,2-propanediol, 50 mg/dL) and a 2-microL aliquot was injected onto the column without prior derivatization or extraction. The other short chain (C2 to C4) alkyldiols were separated by this method and did not interfere with the quantitation of 1,3-butylene glycol. The method was linear (y = 0.0206x + [-0.0073], r = 0.9990) over the range of 25 to 100 mg/dL and the coefficient of variation varied between 0.74 and 6.03%. Minimum detectable concentration of 1,3-butylene glycol was 5.0 mg/dL. The method described is suitable for the rapid detection of potentially toxic blood or plasma levels of 1,3-butylene glycol, as well as for the detection of other short chain glycols.     

Simultaneous detection and quantitation of diethylene glycol, ethylene glycol, and the toxic alcohols in serum using capillary column gas chromatography

Determination of toxic glycols and alcohols in an emergency setting requires a rapid yet accurate and reliable method. To simultaneously determine diethylene glycol (DEG) along with ethylene glycol, methanol, isopropanol, acetone, and ethanol, we modified a previously developed gas chromatographic (GC) method. The system used a Hewlett-Packard 6890 GC with EPC, a Gooseneck splitless liner, and an Rtx-200 capillary column (30 m x 0.53-mm i.d., 3 mm). After serum samples were deproteinized using ultrafiltration (Millipore Ultrafree-MC), 1 mL of the protein-free filtrate was manually injected into the GC. Internal standards for alcohols (and acetone) and glycols were n-propanol and 1,3-butanediol, respectively. All compounds eluted within 3.5 min (linear temperature gradient from 40 to 260 degrees C); total run time was 6.5 min. Limit of detection and linear range for all compounds were 1 or 2.5 mg/dL and 0-500 mg/dL, respectively. In addition, there was no interference from propionic acid, propylene glycol, and 2,3-butanediol. The modifications in the equipment and temperature program allowed increased resolution and thus, detection and reliable quantitation of DEG and other common toxic glycols and alcohols of clinical interest.     

Effects of pyrazole and 3-amino-1,2,4-triazole on methanol and ethanol metabolism by the rat

The metabolism of methanol-¹⁴C and ethanol-1-¹⁴C in rats was evaluated from the rates of ¹⁴CO₂ production. 3-Amino,1,2,4-triazole, a known catalase inhibitor, decreased by 10 and 35 per cent the rates of oxidation of ethanol and methanol, whereas pyrazole, an alcohol dehydrogenase inhibitor, decreased the rates 85 and 50 per cent respectively. However, the simultaneous use of both inhibitors gave the same effects produced by pyrazole alone. Thus the relative contributions in vivo to alcohol metabolism of rat liver alcohol dehydrogenase and catalase-mediated peroxidation, cannot be estimated only in this way. Rat liver alcohol dehydrogenase was purified 14·7 times. At pH 7·0 and 30°, the K_m for methanol was 340 mM and for ethanol 0·26 mM. The V_max/e was 2·36 nM for methanol and 22·3 nM for ethanol (NADH × U^?1 × 1^?1 × sec^?1). 3-Amino-1,2,4-triazole inhibited the purified enzyme with a K_i of 55 mM for methanol and 33 mM for ethanol. The K_i of pyrazole was 2·3 mM for methanol and 2·2 mM for ethanol. The amount of alcohol dehydrogenase present in rat liver, with the found kinetic constants, can account for the ethanol oxidation in vivo, but fails to account, as methanol dehydrogenase, for the observed pyrazole-sensitive methanol oxidation. A mechanism for the complete oxidation of methanol to CO₂ and water through the concerted action of catalase and alcohol dehydrogenase is suggested. 3-Amino-1,2,4-triazole in a dose of 1 g/kg decreases more than 90 per cent of the catalatic activity of catalase, but under certain conditions in vitro, only about 50 per cent of the peroxidative activity of catalase towards methanol and ethanol. Consequently, the degree of catalase-mediated peroxidation should not be controlled or estimated from the residual catalatic activity when using catalase inhibitors. Pyrazole, at a dose of 0·3 g/kg, does not affect catalase activity 1 hr after administration, but decreases it more than 90 per cent after 24 hr. This effect is completely prevented in the presence of alcohol.     

Butanediols: selection, open field activity, and NAD reduction by liver extracts in inbred mouse strains.

Mice from the high-ethanol preferring C57BL strain and low-ethanol preferring DBA strain were tested for their preference for butanediols. The C57BL strain showed a significantly higher preference for a 10% (v/v) solution of 1,3-butanediol than the DBA strain. The C57BL strain also showed a significantly greater consumption of 1,2- and 2,3-butanediol, but the separation between strains was much smaller than with 1,3-butanediol. Both strains uniformly avoided 1,4-butanediol. Tolerance for 1,3-butanediol was tested in an open-field monitor at 3 doses. At the lowest dose the DBA strain was hyperactive and the C57BL were unaffected. At the highest dose both strains were equally depressed. The specific activity of NAD reduction on incubation of liver extracts with 1,3-butanediol and ethanol as substrates was higher with both compounds in extracts from the C57BL strain.     

Interactive effect of combined exposure to glycol ethers and alcohols on toxicodynamic and toxicokinetic parameters

 Ethylene glycol monomethyl ether (EGME) exhibits testicular toxicity and ethylene glycol monobutyl ether (EGBE) is a solvent with haemolytic effects in rats. The study of the interaction of two glycol ethers (EGME and EGBE) and three alcohols (ethanol, n-propanol and n-butanol, 10 or 30 mmol/kg), orally co-administered in male rats, was carried out from a toxicodynamic and toxicokinetic point of view. Administered alone, EGME (10 mmol/kg) caused a 30- and 5-fold increase in the urinary creatine/creatinine ratio at 24 and 48 h, respectively, and 24 h urinary excretion of methoxyacetic acid was of 0.71± 0.042 mmol/24 h (mean±SE). The simultaneous administration of one of the three alcohols at either of the doses mentioned above did not significantly modify the urinary creatine/creatinine ratio (24 and 48 h), or the 24 h urinary excretion of methoxyacetic acid. Administered alone, EGBE (5 mmol/kg) caused an average decrease of 26% in the number of circulating red blood cells and a strong (250 times) increase in the level of plasma haemoglobin 4 h after treatment. Urinary excretion of butoxyacetic acid in rats treated with EGBE (1 mmol/kg) was 0.083±0.0039 mmol/24 h (mean±SE). The simultaneous injection of 30 mmol/kg alcohol (ethanol, n-propanol or n-butanol) almost totally inhibits the haemolytic effect of EGBE, and decreases the urinary excretion of butoxyacetic acid by 43–31%. A strong dose of alcohol (30 mmol/kg) decreases the haemolytic effect due to EGBE, and reduces the urinary excretion of butoxyacetic acid. In contrast, the coadministration of alcohol did not modify the testicular toxicity of EGME, or the 24 h urinary excretion of methoxyacetic acid. It is possible that competitive inhibition of alcohol dehydrogenase by alcohols results in the diversion of EGBE metabolism. Received: 3 July 1995/Accepted: 17 November 1995     

Toxicological assessment of heat transfer fluids proposed for use in solar energy applications,II

Ten commercially available solar heat transfer fluids as well as three samples of used fluids (an ethylene glycol, a propylene glycol, and a silicone fluid) obtained from operating solar hot water systems were evaluated for acute oral toxicity in female rats and for dermal and ocular irritation in female rabbits. Mutagenicity testing was conducted in the Salmonella mutagenicity assay (TA 1538, TA 98, TA 1535, TA 100). Oral LD₅₀ values ranged from 7.0 g/kg for ethylene glycol-based products to >24 g/kg for propylene glycol, hydrocarbon oils, and silicone fluids. None of the solar fluids was mutagenic at the concentrations tested nor caused more than a slight ocular or dermal irritation. No appreciable differences were observed in evaluations between used and unused fluid samples. The results indicate that the fluids may be considered relatively safe for residential solar energy applications, although based on toxicity testing propylene glycol should be preferred over ethylene glycol. Trifluoroethanol (Fluorinol 100) was included in these studies because of its probable use as a working fluid in organic Rankine cycle waste heat recovery systems. Trifluoroethanol had an LD₅₀ of 0.21 g/kg, was not irritating to rabbit skin nor mutagenic in Salmonella, but demonstrated severe ocular toxicity.     

Ethanol - Induced Accumulation of Ethylene Glycol Monoalkyl Ethers in Rats

ABSTRACT

In adult female SPF Sprague-Dawley rats, exposed for 2 hours to 2-methoxy-ethanol (ME, 1600 ppm), 1-acetoxy-2-methoxy-ethane (AME, 800 ppm), 2-ethoxy-ethanol (EE, 420 ppm), or 1-acetoxy-2-ethoxy-ethane (AEE, 170 ppm) the blood level of ME (after ME or AME) or EE (after EE or AEE) was considerably increased after pretreatment with ethanol (20 mmol/kg b.w. i.p.). (ME and EE are metabolites of AME and AEE, respectively.) After i.p. co-administration of ME (10 mmol/kg), EE (10 mmol/kg) or butoxy-ethanol (BE, 2.5 mmol/kg) with ethanol (20 mmol/kg) the blood level of ME, EE, and BE remained nearly constant as long as ethanol levels in blood were above 3 mmol/l. Repeated i.p. dosing (5 times one injection per hour) with EE (4 mmol/kg) or ME (5 mmol/kg) plus ethanol (B or 10 mmol/kg) each resulted in an almost complete accumulation of both ether compounds in the blood. Blood levels of ethanol were increased significantly after EE, but only slightly after ME administration. The prolonged retention of ME, EE, or BE is due to an inhibition of the degradation of these compounds following the competition with ethanol at the alcohol dehydrogenase, the common metabolizing enzyme. This study has demonstrated that glycol ether derivatives are extremely accumulated as long as only very low levels of ethanol are present in blood. Therefore, it is concluded that the elimination of the investigated glycol ethers after occupational exposure can be retarded in alcoholized employees causing an increased health risk of these chemicals following the consumption of alcoholic beverages.     

Effect of pyrazole on rat liver catalase

Pyrazole alone does not affect catalase activity in vitro; however, its administration in vivo produces irreversible inhibition of catalase in rat liver and kidney but not in blood. The inhibition in the liver, after a 70 mg/kg single dose of pyrazole, follows first-order kinetics with a half-life of 8 hr. The activity reaches a minimum at 28 hr followed by gradual recovery at a rate corresponding to a half-life of 1.19 days. This value agrees with previous half-life determinations for rat liver catalase; therefore it is taken as evidence that the irreversibility of the inhibition demonstrated in vitro is also maintained in vivo. The inhibition of catalase is mediated by a product from the metabolism of pyrazole by the microsomal mixed-function oxidase system. This active pyrazole derivative presumably reacts with catalase hydrogen peroxide complex I, and not with the native catalase, in a process that can be prevented by alcohol. It is shown that pyrazole, a drug also used as an alcohol dehydrogenase inhibitor, is eliminated from the liver in a simple exponential process with a half-life of 3.45 hr, which agrees with its reported effects on ethanol metabolism in vivo.     

The induction of ethanol dependence and the ethanol withdrawal syndrome: the effects of pyrazole

Daily administration of an inhibitor of alcohol dehydrogenase (pyrazole, 1 m mol kg^?1, i.p.) appeared to prevent the development of metabolic tolerance to ethanol administered chronically to mice by inhalation, but increased the duration and intensity of the behavioural change associated with ethanol withdrawal, despite the absence of any marked difference in blood or brain ethanol and acetaldehyde concentrations during ethanol administration in the two groups. (Pyrazole-treated mice were exposed to lower concentrations of ethanol.) Changes in brain monoamine concentrations which occur in mice during chronic ethanol administration were not prevented by pyrazole, but differed in time course under these conditions. Repeated administration of pyrazole intraperitoneally caused weight loss and hypothermia in mice, whether or not ethanol was also given. It is concluded that the combination of pyrazole and ethanol is probably not capable of separating primary effects of chronic ethanol administration from secondary (metabolic) effects, and that inhibition of alcohol dehydrogenase is unlikely to be the sole reason for the potentiation of the ethanol withdrawal syndrome by pyrazole.     

Bis(2-methoxyethyl) ether: Metabolism and embryonic disposition of a developmental toxicant in the pregnant CD-1 mouse

An embryotoxic oral dose of bis(2-methoxyethyl) ether (DGDME), 3.73 mmol/kg body wt (500 mg/kg), administered on the 11th day of gestation to pregnant CD-1 mice was metabolized predominantly by O-demethylation to 2-(2-methoxyethoxy)ethanol with subsequent oxidation to (2-methoxyethoxy)acetic acid. Urinary excretion of this metabolite over 48 hr amounted to 63 ± 2% of the dose. A smaller percentage of the administered dose was metabolized at the central ether linkage to produce 2-methoxyethanol, which was further metabolized by alcohol dehydrogenase to methoxyacetic acid. Urinary excretion of methoxyacetic acid, a potent developmental toxicant, amounted to 28 ± 1% of the administered dose by 48 hr and was the second most prominent urinary metabolite. Unchanged DGDME and methoxyacetic acid were detected in the embryonic tissues from these animals, and embryos harvested after the initial 6-hr period showed detectable amounts of only methoxyacetic acid. The average amount of methoxyacetic acid per embryo was calculated to be 1.5 ± 1.0 μmol (5.9 mmol/kg body wt) at the 6-hr termination time. This finding suggests that the reported teratogenic effects of DGDME are due to methoxyacetic acid formed, either in the fetus or by hepatic metabolism in the dam with subsequent distribution to the embryonic tissue. These results suggest that such developmental toxicity may occur with structurally similar aprotic ethylene glycol ethers in which metabolic O-dearylation would yield 2-methoxyethanol.     

Inhibition of 1,4-butanediol metabolism in human liver in vitro

The conversion of 1,4-butanediol (1,4-BD) to gamma-hydroxybutyric acid (GHB), a drug of abuse, is most probably catalyzed by alcohol dehydrogenase, and potentially by aldehyde dehydrogenase. The purpose of this study was to investigate the degradation of 1,4-BD in cytosolic supernatant of human liver in vitro, and to verify involvement of the suggested enzymes by means of gas chromatography–mass spectrometry. The coingestion of 1,4-BD and ethanol (EtOH) might cause complex pharmacokinetic interactions in humans. Therefore, the effect of EtOH on 1,4-BD metabolism by human liver was examined in vitro. Additionally, the influence of acetaldehyde (AL), which might inhibit the second step of 1,4-BD degradation, was investigated. In case of a 1,4-BD intoxication, the alcohol dehydrogenase inhibitor fomepizole (4-methylpyrazole, FOM) has been discussed as an antidote preventing the formation of the central nervous system depressing GHB. Besides FOM, we tested pyrazole, disulfiram, and cimetidine as possible inhibitors of the formation of GHB from 1,4-BD catalyzed by human liver enzymes in vitro. The conversion of 1,4-BD to GHB was inhibited competitively by EtOH with an apparent K _i of 0.56 mM. Therefore, the coingestion of 1,4-BD and EtOH might increase the concentrations and the effects of 1,4-BD itself. By contrast AL accelerated the formation of GHB. All antidotes showed the ability to inhibit the formation of GHB. In comparison FOM showed the highest inhibitory effectiveness. Furthermore, the results confirm strong involvement of ADH in 1,4-BD metabolism by human liver.     

Pyrazole and methylpyrazole for the treatment of 2-butoxyethanol poisoning

2-Butoxyethanol (BE) is a one member of a family of ethylene glycol monoalkyl ethers that are used in a variety of industrial and household products. The clinical features of human and animal BE intoxications mainly include metabolic acidosis, CNS depression and coma, hemolytic anemia, hematuria, and renal injury. It is believed that metabolic activation of BE to butoxyacetic acid (BAA) is responsible for these pathologic changes. The treatment of BE poisoning have been based on an inhibition of the metabolic pathway enzymes which convert BE to toxic metabolites. Therefore, a comparison was made between antidotal properties of pyrazole (PY) and 4-methylpyrazole (MP) in rats subcutaneously intoxicated with BE. It was found that both antidotes effectively protected animals against appearance of hemolytic anemia signs induced by BE. MP appears to be more efficient than PY. These data confirm the beneficial role of alcohol dehydrogenase (ADH) inhibitors in BE intoxication.     

The Measurement of D,L-2,3-Butanediol in Controls and Patients with Alcoholic Cirrhosis

Plasma D,L-2,3-butanediol was measured in 53 controls and 50 patients with alcoholic cirrhosis, none of whom had measurable amounts of blood ethanol. Thirteen of 50 samples from patients with alcoholic cirrhosis had measurable D,L-2,3-butanediol. (range < 5-154 uM). In one patient with alcoholic cirrhosis who had been abstinent from ethanol for over 5 years plasma levels of D,L-2,3-butanediol ranged between 154 and 211 uM over a one-year period. Only one of the 53 control subjects had detectable levels of D,L-2,3-butanediol. Although it has previously been reported that 2,3-butanediol is present in alcoholics consuming distilled spirits (Runstein et al. (1983) Lancet ii, 534), this is the first report of the persistent presence of these compounds in alcoholics in the absence of ethanol. Clearly in abstinent alcoholics the presence of 2,3-butanediol is not due to the ingestion of undistilled spirits nor is it likely to arise directly from the metabolic products of ethanol. The presence of D,L-2,3-butanediol in patients with alcoholic cirrhosis and its absence in control subjects suggests that this compound may be a marker of some forms of alcoholism.