Intestinal absorption of chloral hydrate, free trichloroethanol and trichloroacetic acid in dogs

In order to examine the intestinal absorption of chloral hydrate (CH), free trichloroethanol (F-TCE) and trichloroacetic acid (TCA), an intestinal circulation system in dogs was developed using jejunal, ileal and colonic loops, and solutions of CH, F-TCE and TCA were circulated within them. The concentrations of these substances and their metabolites in the serum, urine, bile and circulates were then measured. In all groups, the fraction of water absorbed from the intestine was about 10% of the administered volume two hours after administration. The absorbed fraction of CH was about 50% in the jejunum and ileum, and about 40% in the colon. The absorbed fraction of F-TCE was about 60% in the jejunum, 50-60% in the ileum and about 40% in the colon, while the figures for TCA were about 40-50% in the jejunum and about 30-40% in the ileum and colon. The combined biliary and urinary excretion ratios of the administered substances and their respective metabolites to the total amounts absorbed from the intestine were about 25-30% for F-TCE, 10-15% for CH and 0.1-0.2% for TCA in all parts of the intestine two hours after administration.     

Comparative study of the effects of chloral hydrate and trichloroethanol on cerebral metabolism

Summary The isolated perfused rat brain was used for a comparative study of the effects of chloral hydrate and trichloroethanol on cerebral energy metabolism. After a perfusion period of 30 min the brain levels of the following substrates and metabolites were measured spectrophotometrically: P-creatine, creatine, ATP, ADP, AMP, glycogen, glucose, glucose-6-P, fructose diphosphate, -glycero-P, dihydroxyacetone-P, pyruvate, lactate, glutamate, -ketoglutarate and ammonia. Furthermore, the concentration of chloral hydrate and trichloroethanol in the isolated brain and in the perfusion medium was measured colorimetrically. Little more than 10% of chloral hydrate in the isolated brain and in the perfusion medium were reduced to trichloroethanol. In intact animals there were about 70% of chloral hydrate transformed. Chloral hydrate and trichloroethanol caused an accumulation of P-creatine, no change in the lactate/pyruvate ratio, an increase of the glucose concentration and a decrease of glucose-6-P level in the isolated brain. The rise of brain glucose level was more pronounced after trichloroethanol than after chloral hydrate. The effects of chloral hydrate and trichloroethanol on brain glucose and glucose-6-P levels suggest an inhibition of brain hexokinase activity by these drugs.Presented in part at the Fifth International Congress on Pharmacology in San Francisco, 1972 (Krieglstein et al., 1972c).     

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.     

Lack of formic acid production in rat hepatocytes and human renal proximal tubule cells exposed to chloral hydrate or trichloroacetic acid

The industrial solvent trichloroethylene (TCE) and its major metabolites have been shown to cause formic aciduria in male rats. We have examined whether chloral hydrate (CH) and trichloroacetic acid (TCA), known metabolites of TCE, produce an increase in formic acid in vitro in cultures of rat hepatocytes or human renal proximal tubule cells (HRPTC). The metabolism and cytotoxicity of CH was also examined to establish that the cells were metabolically active and not compromised by toxicity. Rat hepatocytes and HRPTC were cultured in serum-free medium and then treated with 0.3–3 mM CH for 3 days or 0.03–3 mM CH for 10 days, respectively and formic acid production, metabolism to trichloroethanol (TCE-OH) and TCA and cytotoxicity determined. No increase in formic acid production in rat hepatocytes or HRPTC exposed to CH was observed over and above that due to chemical degradation, neither was formic acid production observed in rat hepatocytes exposed to TCA. HRPTC metabolized CH to TCE-OH and TCA with a 12-fold greater capacity to form TCE-OH versus TCA. Rat hepatocytes exhibited a 1.6-fold and three-fold greater capacity than HRPTC to form TCE-OH and TCA, respectively. CH and TCA were not cytotoxic to rat hepatocytes at concentrations up to 3 mM/day for 3 days. With HRPTC, one sample showed no cytotoxicity to CH at concentrations up to 3 mM/day for 10 days, while in another cytotoxicity was seen at 1 mM/day for 3 days. In summary, increased formic acid production was not observed in rat hepatocytes or HRPTC exposed to TCE metabolites, suggesting that the in vivo response cannot be modelled in vitro. CH was toxic to HRPTC at millimolar concentrations/day over 10 days, while glutathione derived metabolites of TCE were toxic at micromolar concentrations/day over 10 days [Lock, E.A., Reed, C.J., 2006. Trichloroethylene: mechanisms of renal toxicity and renal cancer and relevance to risk assessment. Toxicol. Sci. 19, 313–331] supporting the view that glutathione derived metabolites are likely to be responsible for nephrotoxicity.     

Inhibition by chloral hydrate and trichloroethanol of AMPA-induced Ca(2+) influx in rat cultured cortical neurones

The effects of chloral hydrate and its main metabolite 2,2, 2-trichloroethanol were investigated on the (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)-induced rise of intracellular Ca(2+) concentration ([Ca(2+)](i)) in cultured non-pyramidal cortical neurones of rats by using single-cell fura-2 microfluorimetry. AMPA elicited a concentration-dependent effect that peaked at 300 microM (EC(50), 7. 5 microM). Responses to AMPA (30 microM) were markedly inhibited by superfusion with chloral hydrate (IC(50), 4.5 mM) or trichloroethanol (IC(50), 0.9 mM). By contrast, ethanol (100 mM) caused only slight inhibition. In conclusion, the results demonstrate that chloral hydrate and especially its metabolite trichloroethanol, inhibit the AMPA-induced rise of [Ca(2+)](i) by depressing the entry of Ca(2) into cortical neurones via the AMPA receptor-channel.     

Alteration of chloral hydrate metabolism in rats with carbon tetrachloride-induced liver damage

The metabolism of chloral hydrate (CH) was investigated in the isolated perfused rat liver system. The experiments were performed on rats that were administered carbon tetrachloride (CCl4) subcutaneously for 15 weeks to induce chronic liver damage and on untreated rats. Clearance of CH from the perfusion system was lower in damaged liver than in control liver. In both groups, 50-70% of the added CH was excreted into perfusate as trichloroethanol (TCE) and trichloroacetic acid (TCA) within 120 min. The TCE/TCA ratio was 1:1.3 in the control group compared to 2:1 in the damaged liver group. The findings suggest that CH metabolism in the liver is affected by chronic damage.     

Effects of disulfiram and chloral hydrate on the metabolism of catecholamines in rat liver and brain

Disulfiram and chloral hydrate are known inhibitors of aldehyde dehydrogenase (ALDH), an enzyme involved in the metabolism of dopamine and noradrenaline as well as acetaldehyde. The inhibition in vivo of this enzyme by these drugs was investigated in rat liver and brain by measuring the distribution of catabolites obtained from catechol amines. Incubations of brain and liver tissues as well as perfusions of the caudate nucleus of conscious animals were performed with ¹⁴C-labeled catechol amines. Data from slice incubations revealed that disulfiram at a dose of 200 mg/kg· day given for at least 3 days inhibits brain ALDH more effectively (48 per cent) than the liver enzyme (16 per cent), as measured by the decreased formation of 3, 4-dihydroxyphenylacetic acid. Furthermore, disulfiram increases the rate of deamination of dopamine in liver slices by approximately 25 per cent, but did not alter the rate of dopamine deamination in the brain tissues. Tetrahydropapaverolinc (THP) was formed in every experiment utilizing dopamine. Approximately 10 per cent of the deaminated dopamine was recovered as the alkaloid. In addition, a non-identified metabolite of dopamine was isolated, primarily from incubations of brain tissues. Some, but substantially less, of the non-identified metabolite was obtained from incubations of liver slices as well as from brain perfusions. Chloral hydrate at a dose of 100 $\text{mg}\text{kg}$-day given for at least 3 days did not significantly affect the metabolism of dopamine in either organ. The metabolism of noradrenaline was not significantly altered by either drug. Data from the brain perfusions confirmed the conclusions from incubations of slices: disulfiram is a potent inhibitor of 3, 4-dihydroxyphenylacetic acid formation, while chloral hydrate is virtually ineffective at inhibiting the acid formation. The major differences found from the perfusion studies compared to the slice incubations were in the increased concentration of homovanillic acid (HVA) and the decreased formation of the non-identified metabolite. The finding that disulfiram only inhibited by 16 per cent the liver metabolism of dopamine while drastically inhibiting the liver metabolism of acetaldehyde suggests that different isozymes of aldehyde dehydrogenase are involved in the oxidation of these two aldehydes. The lack of inhibition of 3, 4-dihydroxymandelic acid formation suggests that the aldehyde derived from noradrenaline may be metabolized by still a different isozyme of aldehyde dehydrogenase.     

An eserine-like action of chloral hydrate

The intra-arterial injection of chloral hydrate potentiated the transmission of nerve impulses through the cat superior cervical ganglion, antagonized the ganglionblocking action of hexamethonium, and greatly enhanced the ganglion-stimulant action of acetylcholine. Effects on the ganglion-stimulant actions of carbachol, nicotine, tetramethylammonium and potassium chloride were slight or absent. Chloral hydrate itself usually had no direct stimulant action. The neuromuscular-blocking action of tubocurarine on the isolated rat diaphragm preparation was completely and rapidly reversed by chloral hydrate. This reversal was prevented by previoustreatment of the muscle with neostigmine. Chloral hydrate potentiated the actions of acetylcholine and nicotine on the isolated rabbit duodenum, and, in concentrations exceeding 1 mg/ml., produced a spasm which was abolished by hyoscine but not by mepyramine. It was concluded that these eserine-like effects were manifestations of an anticholinesterase action of chloral hydrate. Neither chloralose nor trichlorethanol showed evidence of this property.     

Studies on the hypnotic effects of chloral hydrate and ethanol and their metabolism in vivo and in vitro

The ED₅₀ values for chloral hydrate, trichloroethanol and ethanol were determined in mice in terms of loss of righting reflex. Co-administration of chloral hydrate and ethanol had an additive effect, but both chloral hydrate and trichloroethanol at subhypnotic doses significantly prolonged ethanol sleeping time. Chloral hydrate and ethanol, given together, yielded lower blood ethanol levels than when ethanol was given alone. Chloral hydrate was reduced by liver alcohol dehydrogenase (K_m = 7.5 mM). Trichloroethanol was not a substrate for the enzyme but inhibited ethanol oxidation competitively (K_i = 1.38 × 10^?5 M). It is proposed that chloral hydrate metabolism to trichloroethanol is increased by ethanol and that this is responsible for the prolonged sleep time.     

高效液相色谱法测定水合氯醛口服溶液含量

目的:建立测定水合氯醛含量的高效液相色谱方法.方法:采用Shim-pack GIST C18色谱柱(4.6 mm×250 mm,5μm),以乙腈-水(10:90)为流动相,流速1.0 mL·min-1,检测波长210 nm,柱温35℃.结果:水合氯醛浓度在0.4011～1.604 mg·mL-1范围内呈良好线性关系(r...