Metabolism of trichloroethylene in man

Groups of 5 to 6 volunteers each participated in three experimental series involving inhalation of analytically controlled trichloroethylene concentrations for 6 h daily on 5 successive week days: (a) 50 ppm constant, (b) 250 ppm for 12min/h (high peak concentrations, average 50 ppm); (c) 100 ppm constant. The trichloroethanol (TCE) levels in the blood were determined 3 times daily, the TCE and trichloroacetic acid (TCA) levels in the urine twice daily by means of gas Chromatographic (TCE) and colorimetric (TCA) techniques. It was seen that TCE accumulates in the blood from day to day reaching maximum values of (a) 2.0 g/ml, (b) 2.5 g/ml, or (c) 5.0 g/ml; the half life of TCE in the blood was 12 h in each case. After a single dose of 15 mg/kg chloral hydrate (normal hypnotic dose) TCE reached levels of approx. 7 g/ml within 1 h; the pattern of elimination was identical to that obtained after Tri inhalation. The maximum TCE value after 100 ppm Tri coincides with that obtained 2 to 2 1/2 h after ingestion of chloral hydrate. There are some data in the literature indicating that such TCE levels reduce the performance ability in vigilance tests. The formation and accumulation of TCE probably is responsible for the psycho-organic syndrome encountered during occupational exposure to Tri.On inhalation of Tri for several days the urinary excretion of TCE and TCA does not follow certain rules which may be derived from single experiments (for instance, 6 h-inhalations). It would appear, therefore, that the procedures described in the literature for assessment of Tri exposure on the basis of TCE and/or TCA excretion are subject to revision.The described study was supported by the Deutsche Forschungsgemeinschaft.     

Effect of ethanol on the metabolism of trichloroethylene

Trichloroethylene (TCE) is metabolized to chloral hydrate (CH) by the cytochrome P-450 monooxygenase system. CH can either be oxidized by chloral hydrate dehydrogenase to trichloroacetic acid (TCA) or reduced by alcohol dehydrogenase to trichloroethanol (TCEtOH). The oxidation reaction requires NAD+, while the reduction reaction requires NADH. Since ethanol (EtOH) is known to alter the NAD+/NADH ratio in the hepatocyte, it was coadministered with TCE in an attempt to alter the metabolism of TCE. This would provide a means for predicting interactions of ethanol on the hepatotoxicity and carcinogenicity of TCE. Male Sprague-Dawley rats were administered oral doses of either 1.52, 4.56, or 22.8 mmol/kg TCE, with the treatment group receiving an additional 1.52, 4.56, or 22.8 mmol/kg EtOH, respectively. Blood and urine samples were collected over 72 h. The clearance of TCE appeared to be saturated at the 4.56 mmol/kg dose, as evidenced by prolonged residence times for TCE in the body. Consistent with this result, there was an attenuation of the increases in the levels of TCEtOH and TCA in blood. However, the time to peak concentration of these metabolites was delayed with increasing doses and their residence time in the body was prolonged. Therefore, the area under the curve (AUC) for TCEtOH and TCA continued to increase with the higher doses of TCE. Measurement of the net output of these metabolites in urine confirmed that, although metabolism was saturated, the net metabolic conversion of TCE increased. As predicted, EtOH decreased blood levels of TCA, but only at early times at the high dose. EtOH did increase the urinary TCEtOH/TCA ratio at all dose levels. These results are consistent with the hypothesis of a more reduced state in the hepatocyte caused by the generation of excessive reducing equivalents by EtOH metabolism. The metabolism of TCE is shifted toward reduction to TCEtOH, away from oxidation to TCA. However, the effect was prominent only at extremely high doses of TCE and EtOH.     

EFFECT OF ETHANOL ON THE METABOLISM OF TRICHLOROETHYLENE IN THE PERFUSED RAT LIVER

The effect of 2 m M ethanol, a concentration indicative of daily alcohol consumption, was investigated on trichloroethylene (TRI) metabolism in perfused Wistar rat liver. The study consisted of two parts: The first part studied TRI administration with or without ethanol. In the second study chloral hydrate (CH), an intermediate in TRI metabolism, was administered in the absence or presence of ethanol to phenobarbital (PB) treated or non-PB-treated rats. The concentrations of the metabolites, total trichloroethanol (TCE), and trichloroacetic acid (TCA) were measured by gas chromatography and intracellular reduced pyridine nucleotides by surface fluorometry. In the first study, ethanol infusion significantly increased the TCE/TCA ratio, TCE production rate, and percentage of reduced pyridine nucleotides, and decreased TCA production rate without an associated change in the sum of TCE and TCA formation rates. In the second study, ethanol infusion in the absence or presence of PB produced similar significant increases in the TCE/TCA ratio, TCE production rate, and percentage of reduced pyridine nucleotides, accompanied by a decrease in TCA formation. The observed shift in TRI metabolism in the presence of ethanol, from oxidation to TCA to reduction to TCE, suggests that alcohol exerts alterations in hepatic intracellular oxidation-reduction (redox) states.     

Trichloroethylene inhibits aldehyde dehydrogenase only for aliphatic aldehydes of short chains in rats

The effects of trichloroethylene (TCE) administration on aldehyde dehydrogenase (ALDH) and cytochrome P450 isozymes were studied in rats and compared with those of methanol. Intragastric administration of TCE to rats at 0.05 or 0.2 ml/kg for 1 week significantly inhibited ALDH activity for aliphatic aldehydes of short chains in the mitochondrial and cytosolic fractions of rat liver, respectively, but had no effect on the activity for long chain aliphatic aldehydes. ALDH activity catalyzing the metabolism of some aromatic aldehydes was even induced by TCE. Microsomal ALDH activity was not decreased by TCE treatment. A kinetic study showed that the low-Km isozyme of ALDH for propionaldehyde in mitochondrial and cytosolic fractions was inhibited by TCE treatment. Addition of TCE, trichloroethanol or trichloroacetic acid to the in vitro assay system did not affect the activity for acetaldehyde, but chloral hydrate at 0.02 mM decreased the activity by 42 and 35% in cytosol and the 700 x g supernatant, respectively. Methanol treatment, on the other hand, had no effect on any ALDH activity. Both TCE and methanol significantly induced CYP2E1 in rat liver. The combined effects of TCE on ALDH and cytochrome P450 may account for the degreasers' flush. Exposure to TCE and methanol may result in a change in the metabolism and toxicity of other chemicals.     

Subchronic toxicity of chloral hydrate on rats: a drinking water study

The subchronic toxicity of chloral hydrate, a disinfection byproduct, was studied in rats following 13 weeks of drinking water exposure. Male (262 +/- 10 g) and female (190 +/- 8 g) Sprague-Dawley rats, ten animals per group, were administered chloral hydrate via drinking water at 0.2, 2, 20 and 200 ppm. Control animals received distilled water only. Gross and microscopic examinations, serum chemistry, hematology, biochemical analysis, neurogenic amine analysis and serum trichloroacetic acid (TCA) analysis were performed at the end of the treatment period. Bronchoalveolar fluids were collected at necropsy and urine specimens were collected at weeks 2, 6 and 12 for biochemical analysis. No treatment-related changes in food and water intakes or body weight gains were observed. There were no significant changes in the weights of major organs. Except for a mild degree of vacuolation within the myelin sheath of the optic nerves in the highest dose males, there were no notable histological changes in the tissues examined. Statistically significant treatment-related effects were biochemical in nature, with the most pronounced being increased liver catalase activity in male rats starting at 2 ppm. Liver aldehyde dehydrogenase (ALDH) was significantly depressed, whereas liver aniline hydroxylase activity was significantly elevated in both males and females receiving the highest dose. A dose-related increase in serum TCA was detected in both males and females starting at 2 ppm. An in vitro study of liver ALDH confirmed that chloral hydrate was a potent inhibitor, with an IC(50) of 8 micro M, whereas TCA was weakly inhibitory and trichloroethanol was without effect. Analysis of brain biogenic amines was conducted on a limited number (n = 5) of male rats in the control and high dose groups, and no significant treatment-related changes were detected. Taking into account the effect on the myelin sheath of male rats and the effects on liver ALDH and aniline hydroxylase of both males and females at the highest dose level, the no-observed-effect level (NOEL) was determined to be 20 ppm or 1.89 mg kg(-1) day(-1) in males and 2.53 mg kg(-1) day(-1) in females. This NOEL is ca. 1000-fold higher than the highest concentration of chloral hydrate reported in the municipal water supply.     

Development of an animal model of solvent abuse for use in evaluation of extreme tricholoroethyylene inhalation

Self-intoxication by inhalation of vapors of trichloroethylene (TCE) and other solvents in widespread. In order to develop exposure protocols which typify episodes of TCE “sniffing”, male Wistar-Munich rats were exposed to TCE vapor levels ranging from 9000 to 16 000 ppm. TCE in concentrations of 14 000 ppm and greater quickly produced loss of righting reflex. Recovery from the narcosis was very rapid. Central nervous system (CNS) depression was found to be cumulative in rats subjected for 5 h to alternating periods of 5 min of 15 000 ppm TCE and 15 min of fresh air. Ethanol markedly potentiated depression in these subjects. No evidence of liver or kidney damage was seen in rats subjected to the repetitive 5-h TCE inhalation regimen, nor in rats fasted for 16 h before the TCE-exposure session. Oral admnistration of 5 ml/kg body wt of ethanol 1 h, 16 h, or once daily for 3 days before the TCE-exposure regimen had little if any potentiating effect on hepatorenal toxicity potential. Animals that received ethanol and were fasted before TCE exposure exhibited slight elevations in SGOT and SGPT levels.     

Ethanol-induced enhancement of trichloroethylene metabolism and hepatotoxicity: difference from the effect of phenobarbital

Male Wistar rats pretreated with ethanol (2.0 g in 80 ml liquid diet/day for 3 weeks) or phenobarbital (PB, 80 mg/kg/day ip for 4 days) were exposed by inhalation to 500, 1000, 2000, 4000, or 8000 ppm trichloroethylene (TRI) for 2 or 8 hr, and the blood concentration of TRI and the urinary concentration of TRI metabolites (trichloroethanol (TCE) and trichloroacetic acid (TCA] were determined at various times. Plasma glutamic-pyruvic transaminase (GPT) activity was measured 22 hr after the end of exposure as an indicator of hepatic damage. Both ethanol and PB enhanced TRI metabolism as evidenced by accelerated disappearance of TRI from the blood and increased excretion of total trichloro compounds (TCE + TCA) in the urine. However, the effects of ethanol and PB were different from each other: ethanol markedly enhanced the metabolism particularly at TRI concentration of 2000 ppm or lower, whereas PB enhanced it only at 4000 ppm or higher. This difference was also reflected in the effect of TRI on liver: ethanol potentiated TRI hepatotoxicity more markedly than did PB when TRI concentration remained 2000 ppm or lower, whereas PB potentiated the toxicity more markedly than ethanol when the concentration was 4000 ppm or higher. It is noteworthy that ethanol potentiated TRI hepatotoxicity at a TRI concentration as low as 500 ppm. The severity of hepatic damage expressed by plasma GPT activity essentially paralleled the urinary excretion rate of total trichloro compounds during and 4 hr after exposure (r = 0.87 to 0.93). Compared between the contribution of concentration and duration of exposure to the toxicity, a higher concentration of TRI tended to cause more severe liver damage to PB-treated rats than did a prolonged period of exposure, whereas the toxicity in ethanol-treated rats was generally more marked in rats exposed to TRI for a longer period than in rats exposed to a higher concentration.     

Mechanistic studies on chloral toxicity: relationship to trichloroethylene carcinogenesis

Chloral (trichloroacetaldehyde), the major metabolite of trichloroethylene (TCE), was investigated for its potential to form DNA-protein cross-links (DPX), a lesion produced by other aldehydes. Chloral did not form DPX in rat liver nuclei at concentrations up to 250 mM for 30 min at 37 degrees C, while chloroacetaldehyde (47 mM) and acetaldehyde (200 mM) did form cross-links. Experiments with the aldehyde-trapping reagents thiosemicarbazide and semicarbazide showed that chloral did not react, in contrast with aldehydes that form DPX. This indicates a very strong hydration of chloral. Mice given 800 mg/kg [14C]chloral after pretreatment with 1500 mg/kg TCE for 10 days had no detectable covalent binding of 14C to DNA in the liver. These results do not support a genotoxic theory of carcinogenesis for TCE mediated through chloral.     

Alteration of the enzymology of chloral hydrate reduction in the presence of ethanol.

The enzymology of chloral hydrate reduction to trichloroethanol was studied in rat liver slices and homogenates. Two enzymes capable of reducing chloral hydrate are present in rat liver and by their properties were found to be aldehyde reductase and alcohol dehydrogenase. The alcohol dehydrogenase catalyzed reaction was very sensitive to the NAD/NADH ratio of the incubation medium and was found to be virtually incapable of performing the reduction with a simulated in vivo coenzyme ratio. The aldehyde reductase catalyzed reaction was relatively insensitive to the NADP/NADPH ratio. Hence, only one of the two possible enzyme systems appears to catalyze the reduction in vivo. Incubations performed with liver slices in the presence or absence of inhibitors and alternative substrates for the two enzyme systems indicated that in the absence of ethanol only aldehyde reductase catalyzed the reduction of chloral hydrate. About a 1.5-fold increase in the rate of reduction of chloral hydrate was observed when 40 mM ethanol was added to the liver slice incubation. Further, deuterium was incorporated into trichloroethanol when the incubations were performed with deuteroethanol. The increased rate of reduction and the deuterium incorporation were both prevented by the inclusion of alcohol dehydrogenase inhibitors (pyrazole and isobutyramide). Thus, in the presence of ethanol, both alcohol dehydrogenase and aldehyde reductase contribute to the reduction of chloral hydrate. Alcohol dehydrogenase is capable of reducing chloral hydrate in the presence of an oxidizable alcohol because it is converted into an enzyme—NADH complex which can then reduce the compound.     

Inhibition of alcohol dehydrogenase by chloral hydrate and trichloroethanol: possible role in the chloral hydrate-ethanol interaction

Both chloral hydrate and trichloroethanol inhibited mouse liver alcohol dehydrogenase (LADH) in vitro. The inhibition of LADH by chloral hydrate appears to be non-competitive in nature with an inhibition constant (Ki) of about 2.7 X 10(-4) M. The inhibition of LADH by trichloroethanol was competitive and the (Ki) was about 2.7 X 10(-5) M. The elimination of ethanol from the blood and brain was significantly reduced in chloral hydrate- or trichloroethanol-pretreated mice. Since reduced elimination of ethanol could result in the prolongation of its central depressant activity, we suggest that this should be considered as a factor in the enhanced pharmacological effects of ethanol-chloral hydrate mixtures.     

Induction of strand breaks in DNA by trichloroethylene and metabolites in rat and mouse liver in vivo

The ability of trichloroethylene (TCE) and selected metabolites to induce single-strand breaks in hepatic DNA of male B6C3F1 mice and Sprague-Dawley rats in vivo was evaluated using an alkaline unwinding assay. Doses of TCE of 22-30 mmol/kg were required to produce strand breaks in DNA in rats, whereas a dose of 11.4 mmol/kg was sufficient to increase the rate of alkaline unwinding in mice. To assess the importance of TCE metabolism to this response, rats were subjected to pretreatments of ethanol, phenobarbital, TCE, or the appropriate vehicle for 4 days prior to challenge doses of TCE. Phenobarbital and TCE, but not ethanol pretreatments, reduced the dose of TCE required to produce significant increases in single-strand breaks. In another series of experiments, mice and rats were treated with metabolites of TCE. Trichloroacetate, dichloroacetate, and chloral hydrate induced strand breaks in hepatic DNA in a dose-dependent manner in both species. Strand breaks in DNA were observed at doses that produced no observable hepatotoxic effects as measured by serum aspartate aminotransferase and alanine aminotransferase levels. The slopes of the dose-response curves and the order of potency of these metabolites differed significantly between rats and mice, suggesting that different mechanisms of single-strand break induction may be involved in the two species. These data provide a potential explanation for the different sensitivity of mice and rats to the hepatocarcinogenic effects of TCE.     

Biochemical effects of chloral hydrate on male rats following 7-day drinking water exposure

The biochemical and toxicological effects of chloral hydrate were investigated. Four groups (n = 7 per group) of male Sprague-Dawley rats (161-170 g) were administered chloral hydrate in drinking water at concentrations of 20, 200 or 2000 ppm for 7 days. The control group received phosphate-buffered water only. There were no treatment-related changes in the body weight gains, relative weights of major organs or haematological parameters. Trichloroacetic acid was significantly (P < 0.05) elevated in the serum of high-dose animals (7.75 +/- 5.14 mg dl(-1), mean +/- SD). In the high-dose animals there was a 36% increase in protein level in the liver homogenates but not in the corresponding 9000 g supernatants. Concurrently, there was a threefold increase in the activity of the hepatic peroxisomal enzyme palmitoyl CoA oxidase (PCO). A prominent change was the dose-related suppression in hepatic aldehyde dehydrogenase (ALDH) activity observed in all treatment groups, with the decrease ranging from 15% at 20 ppm to 68% at 2000 ppm. There were no significant decreases in the activity of hepatic enzymes ethoxyresorufin O-deethylase (EROD), benzyloxyresorufin O-dealkylase (BROD) and UDP-glucuronosyl-transferase (UDPGT). In the high-dose group there was a 30% increase in hepatic glutathione-S transferase (GST) activity, accompanied by a 13% increase in glutathione (GSH). Significant effects on lipids were observed in the liver of the high-dose animals, with a 15% decrease in hepatic cholesterol and triglyceride levels. There were no treatment-related changes in serum chemistry parameters, including cholesterol and triglyceride levels. Although in vitro assays showed chloral hydrate to be an inhibitor of serum pseudocholinesterase activity, with a 50% inhibition concentration (ic(50)( of approximately 0.7 mM at 5 mM butyrylthiocholine, no decrease in serum pseudocholinesterase activity was found in the treated animals. It was concluded that the liver is the target organ for chloral hydrate, with suppression of ALDH as the most sensitive endpoint followed by alteration in the GSH level and GST activity. Changes observed in the high-dose animals, such as increased peroxisomal PCO activity in the liver and perturbation of lipid homeostasis in the liver and blood, were likely to be associated with trichloracetic acid, the major metabolite of chloral hydrate.     

Effects of some centrally acting drugs on acetylcholine synthesis by rat cerebral cortex slices

1. Brain cortex slices from rats injected i.p. with urethane (1 g/kg), chloral hydrate (350 mg/kg) or physostigmine (0.75 mg/kg) were examined for acetylcholine (ACh) content, cholinesterase (total enzyme) activity and formation of (14)C-ACh from carbon (14)-uniformly labelled glucose (U-(14)C-D-glucose) in the presence of 0.01 mM physostigmine.2. Slices from rats treated with urethane, chloral hydrate, or physostigmine contained significantly higher concentrations of ACh than slices from untreated animals.3. Only slices from physostigmine-treated rats had a significantly lower cholinesterase activity.4. Slices from urethane- or chloral hydrate-treated animals formed significantly less (14)C-ACh than slices from untreated or physostigmine-treated rats when incubated in 4 mM K(+) medium. In an ACh-releasing medium (31 mM K(+)) slices from rats treated with urethane or chloral hydrate and slices from untreated rats formed similar amounts of (14)C-ACh.5. Slices from rats treated with atropine (25 mg/kg) or pentylenetetrazol (75 mg/kg) had a similar ability to form (14)C-ACh as slices from untreated animals when incubated in either 4 or 31 mM K(+) medium.6. These findings suggest that the intraneuronal ACh concentration is a limiting factor in the regulation of ACh synthesis.     

Effect of 4-methylpyrazole and pyrazole on the induction of fatty liver by a single dose of ethanol

Pyrazole (272 mg/kg), 4-methylpyrazole (4-MP; 200 mg/kg) or saline was injected intraperitoneally into fasted male and female rats. Ten min later, ethanol (4 or 6 g/kg) or an equicaloric dose of sucrose was given by stomach tube. Hepatic triglyceride (TG) levels were measured at 6, 12 or 16 hr after the gavage. With a 4 g/kg dose of ethanol, pyrazole reduced the accumulation of TG at 6 hr in females, but not at 12 and 16 hr. In males, ethanol gave relatively little TG accumulation at 6 hr and pyrazole did not affect this, but at 16 hr the TG levels in the ethanol-pyrazole group had not risen as much as in the ethanol-saline group. In contrast to pyrazole, 4-MP by itself increased liver TG content, and significantly increased the TG accumulation caused by a 4 g/kg dose of ethanol in both males and females at 16 hr. However, 4-MP caused a significantly smaller TG accumulation in females at 6 hr after the ethanol, but not in males. With a larger dose of ethanol (6 g/kg), both pyrazole and 4-MP decreased the accumulation of TG at 16 hr in males. It is concluded that ethanol per se, ethanol as a metabolic substrate, and pyrazoles as pharmacological agents with complex actions may all contribute to the development of acute fatty liver. Therefore, pyrazole and 4-MP do not appear to be suitable tools for resolving the controversy about the mechanism of production of alcoholic fatty liver.     

乙醇、水合氯醛和纳洛酮 3药相互作用的定量分析(英文)

目的 :采用Q指数法、等效线法和多元逻辑Logistic回归学模型来评价乙醇、水合氯醛以及纳洛酮相互作用。方法 :观察 3种药物对昆明种小鼠催眠作用的影响。在 2药相互作用研究中 ,水合氯醛与乙醇按不同比例给予 (2 5∶75 ,5 0∶5 0 ,78∶2 2和 80∶2 0 )。在 3药相互作用研究中 ,在给予纳洛酮固定剂量 (0 .5mg·kg- 1和 0 .2mg·kg- 1) 15min后 ,混合给予水合氯醛与乙醇 (按照 1∶1和 1∶3比例 )来诱导睡眠。水合氯醛、乙醇 ,纳洛酮以及它们混合物的催眠作用 (翻正反射消失 )ED50 代入等效线、Q test和多元逻辑回归模型进行计算。结果 :在 2药物相互作用研究中 ,水合氯醛与酒精呈现明显协同作用。 3个药物相互作用研究中 ,随着纳洛酮剂量改变而呈现不同情况。结论 :乙醇与水合氯醛在诱导睡眠方面有协同作用 ,但是在加入固定剂量的纳洛酮后 ,整体可呈现拮抗作用 ,这与本研究讨论中阐述的药理机制相符合     

Synergistic action of pyrazole on ethanol incoordination: differential metabolic and central nervous system effects

The influence of pyrazole on ethanol-induced incoordination was measured by a modified tilting-plane technique. Pyrazole (1–77 mmol/kg; 120 mg/kg) and/or ethanol (32.6 mmol/kg; 1.5 g/kg) was given intraperitoneally to rats. Impairment of coordination was related to blood ethanol concentrations. The mean maximal impairment was significant in all conditions. For ethanol alone the maximal impairment was 8.7%, for pyrazole alone 4.8% and for ethanol + pyrazole 16.5 %. Ethanol alone induced a total impairment, assessed planimetrically, of 530 units. Pyrazole alone induced an impairment gradually increasing with time (totally 1070 units). When pyrazole was combined with ethanol, the rate of ethanol elimination was reduced by 81%, and the time it remained in the blood was prolonged from 196 ± 11 to 850 ± 16 min. The rate of disappearance was reduced from 8.05 to 1.57 μg/ml per min. The total impairment increased to 5600 units, indicating a synergistic interaction between ethanol and pyrazole, which is contrary to the normalizing effects of pyrazole on ethanol-induced metabolic changes. A “post-drug” impairment was observed one week after pyrazole, while no such effects were found after repeated administration of saline or ethanol alone in control animals. Thus, pyrazole showed acute and long-term toxic eifects.     

Metabolism of [3H]dopamine following intracerebroventricular injection in rats pretreated with ethanol or chloral hydrate

The metabolism of [3H]dopamine injected into the lateral cerebroventricles, was studied in rats after treatment with either ethanol or chloral hydrate. The experimental system was designed primarily to detect the possible conversion of dopamine to the tetrahydroisoquinoline derivatives, tetrahydropapaveroline, salsolinol and O-methylsalsolinol. With or without pretreatment with ethanol or chloral hydrate, no conversion of [3H]dopamine to [3H]tetrahydroisoquinolines was detected. The limits of detection per rat brain were: tetrahydropapaveroline less than 1.6 X 10(-14) moles (0.00032% conversion), salsolinol less than 1.6 X 10(-13) moles (0.00032% conversion), and 6- and 7-O-methylsalsolinol less than 3.2 X 10(-14) moles (0.00032% conversion). Two consistent ethanol- or chloral hydrate-induced alterations in [3H]dopamine metabolism were noted: (1) small but statistically significant increases in the ratios of reduced to oxidized metabolites resulting from monoamine oxidase action; and (2) decreased relative amounts of N-methylated metabolites.     

A fatality due to an accidental methadone substitution in a dental cocktail

A 6-year-old male child was scheduled for a dental procedure requiring conscious sedation. Prior to the procedure, the child was administered a dental cocktail containing chloral hydrate, hydroxyzine, and methadone. After returning from the dentist, the child appeared groggy and was allowed to sleep. A few hours later, he was found unresponsive, and following resuscitation attempts at a local medical center, he was pronounced dead. Toxicological analyses of femoral blood indicated the presence of hydroxyzine at less than 0.54 μg/mL, trichloroethanol (TCE) at 8.3 μg/mL, and methadone at 0.51 μg/mL. No meperidine was detected. The cause of death was reported to be due to the toxic effects of methadone. The toxicological analysis was corroborated by the analysis of the contents of the dental cocktail, which revealed the presence of hydroxyzine, chloral hydrate, and methadone. Residue from a control sample obtained from the same pharmacy, but administered to a different subject, was found to contain hydroxyzine, chloral hydrate, and meperidine. This report represents the first known fatality due to accidental substitution of methadone in a dental cocktail.     

A search for residual behavioral effects of trichloroethylene (TCE) in rats exposed as young adults

Trichloroethylene (TCE) is an organic solvent with robust acute effects on the nervous system, but poorly documented long-term effects. This study employed a signal detection task (SDT) to assess the persistence of effects of repeated daily inhalation of TCE on sustained attention in rats. Adult male Long-Evans rats inhaled TCE at 0, 1600, or 2400 ppm, 6 h/day for 20 days (n=8/group) and began learning the SDT 3 weeks later. Rats earned food by pressing one retractable response lever in a signal trial and a second lever in a blank (no signal) trial. TCE did not affect acquisition of the response rule or performance of the SDT after the intertrial interval (ITI) was changed from a constant value to a variable one. Increasing the trial presentation rate reduced accuracy equivalently in all groups. Injections of ethanol (0, 0.5, 1.0, 1.5 g/kg ip) and d-amphetamine (0, 0.1, 0.3, 1.0 mg/kg sc) systematically impaired performance as functions of drug dose. d-Amphetamine (1.0 mg/kg) reduced P(hit) more in the 2400-ppm TCE group than in the other groups. All rats required remedial training to learn a reversal of the response contingencies, which TCE did not interfere with. Thus, a history of exposure to TCE did not significantly alter learning or sustained attention in the absence of drugs. Although ethanol did not differentially affect the TCE groups, the effect of d-amphetamine is consistent with solvent-induced changes in dopaminergic functions in the CNS. Calculations indicated power values of 0.5 to 0.8 to detect main effects of TCE for the three primary endpoints.     

Identification of trichloroethylene and its metabolites in human seminal fluid of workers exposed to trichloroethylene.

We have investigated the potential of the male reproductive tract to accumulate trichloroethylene (TCE) and its metabolites, including chloral, trichloroethanol (TCOH), trichloroacetic acid (TCA), and dichloroacetic acid (DCA). Human seminal fluid and urine samples from eight mechanics diagnosed with clinical infertility and exposed to TCE occupationally were analyzed. In in vivo experimental studies, TCE and its metabolites were determined in epididymis and testis of mice exposed to TCE (1000 ppm) by inhalation for 1 to 4 weeks. In other studies, incubations of monkey epididymal microsomes were performed in the presence of TCE and NADPH. Our results showed that seminal fluid from all eight subjects contained TCE, chloral, and TCOH. DCA was present in samples from two subjects, and only one contained TCA. TCA and/or TCOH were also identified in urine samples from only two subjects. TCE, chloral, and TCOH were detected in murine epididymis after inhalation exposure with TCE for 1 to 4 weeks. Levels of TCE and chloral were similar throughout the entire exposure period. TCOH levels were similar at 1 and 2 weeks but increased significantly after 4 weeks of TCE exposure. Chloral was identified in microsomal incubations with TCE in monkey epididymis. CYP2E1, a P450 that metabolizes TCE, was localized in human and monkey epididymal epithelium and testicular Leydig cells. These results indicated that TCE is metabolized in the reproductive tract of the mouse and monkey. Furthermore, TCE and its metabolites accumulated in seminal fluid, and suggested associations between production of TCE metabolites, reproductive toxicity, and impaired fertility.