Massive hepatic necrosis after fluroxene anesthesia--a case of drug interaction?

Potentiation of BrCCl3 hepatotoxicity by chlordecone: biochemical and ultrastructural study

Previous work has established that chlordecone (CD) potentiates the hepatotoxicity of BrCCl3. This interaction occurs at nontoxic levels of CD and BrCCl3. The present research was designed to investigate the mechanism governing the pathogenesis of potentiated hepatic injury and lethality induced by a low dose of BrCCl3 after dietary pretreatment with 10 ppm of CD for 15 days. On Day 16, a single dose of BrCCl3 (30 microliters/kg) was administered ip to rats maintained either on normal diet (ND) or on a diet contaminated with 10 ppm CD. Blood and liver samples were collected at 0, 3, 6, 12, 24, 36, and 48 hr after the halomethane administration for biochemical (ATP, bilirubin, glycogen) and for ultrastructural studies. A continuous increase in serum bilirubin and decrease in hepatic ATP and glycogen were observed in CD + BrCCl3 combination, indicating progressive injury, but not in other treatment groups. In ND + BrCCl3 combination, all biochemical indices were either normal or close to normal after 36 hr, suggesting complete recovery from hepatotoxicity. The most extensive ultrastructural changes characteristic of halomethane hepatotoxicity (necrosis, ballooned cells, and dilation of rough endoplasmic reticulum) were observed after the CD + BrCCl3 combination treatment. The progressive and early depletion of hepatic ATP and glycogen, and the progressive increase in toxicity along with decreased cell division in CD + BrCCl3-treated rats, indicate the association of compromised energy status and suppression of cell division and tissue repair in CD-potentiated BrCCl3 toxicity. These findings suggest that the suppression of stimulated hepatocellular regeneration results in the loss of the essential mechanism of tissue repair leading to continuation of the toxic liver injury associated with the CD + BrCCl3 combination treatment.

2,2,2-Trifluoroethanol toxicity in aged rats

Various anesthetics are metabolized by different forms of cytochrome P-450 yielding the same toxic metabolite, 2,2,2-trifluoroethanol (TFE). The toxicity of TFE is a consequence of its metabolism catalyzed by cytochrome P-450. Since a marked age difference exists in the composition and inducibility of the hepatic mixed function oxidase system, we have elucidated the toxicity of TFE in 36-month-old aged Wistar rats. The aged rats were injected with sublethal doses of TFE (0.10 g/kg once per week for 5 weeks), after which they were sacrificed for pathologic examination. The major TFE-related lesions observed were severe hepatocyte degenerative changes such as basophilic, eosinophilic, vacuolated hepatocytes, bile duct hyperplasia, accumulation of lipofuscin pigments, and preneoplastic nodules. Other changes seen were the hyalinization of gastric submucosal wall, generalized testicular atrophy due to the loss of seminiferous tubules, coagulation necrosis of intestinal mucosal wall, hyperpigmentation, and more advanced and severe chronic progressive glomerulonephropathy in the TFE-treated rats. More severe lipofuscin and vacuolation of white matter of thalamic area, pons, midbrain, and cerebellum reflective of enhanced aging were also seen. Ultrastructural studies of liver from TFE-treated rats revealed rather diffuse loss of glycogen, fragmentation of endoplasmic reticulum, mineralization of mitochondria, and loss of other organelles within the hepatocytes versus saline-treated aged rats. Hepatic cytochrome P-450 concentrations, measured as a possible index of endoplasmic reticulum damage, were not affected by TFE administration.

2,2,2-Trifluoroethanol-induced enteropathy in rats: chemically or bacterially mediated effects

The lethal effects of the fluorinated ether anesthetic, fluroxene, in rats are a consequence of its metabolism, which is catalyzed by cytochrome P-450 to the toxic metabolite 2,2,2-trifluoroethanol (TFE). The anesthetic or TFE (0.21 g/kg) caused decreased white blood cell counts, necrosis of bone marrow and lymphocytes, and decreased small intestine dry weight and was associated with septicemia. To elucidate the mechanism of TFE toxicity in rats we undertook histopathologic, ultrastructural and bacteriologic studies. TFE produced severe edema of intestinal lamina propria and submucosae, dilatation of crypts, loss of surface epithelium, vacuolation and necrosis of intestinal epithelial cells, and infiltration of polymorphonuclear leukocytes into the edematous lamina propria. Intestinal epithelial villi lost their cellular tissue integrity. Coccobacillary organisms were numerous in the ulcerated intestine. Hemolytic E. coli were isolated from intestinal tissue at a two-log increase in concentration relative to controls. Hemograms from TFE-treated rats exhibited marked leukopenia and morphologic differences. The platelets lost their discoid shape, extended pseudopods, and centralizing granules. Hemoglobin precipitation as Heinz bodies and crystalloid structures was observed in TFE-treated rats. Together the data suggest that TFE-induced enteropathy was most probably due to E. coli precipitated from TFE-mediated alterations in the population of small intestinal microbes. The antibiotics erythromycin, active against gram-positive bacteria, and streptomycin, active against gram-negative bacteria, and the antiendotoxin, polymyxin B, were administered to rats prior to TFE in an effort to differentiate between these mechanisms by altering the intestinal bacteria populations. The results indicate that the TFE-induced small intestinal lesions are initiated by the direct focal necrotic effect of TFE or its metabolites on the small intestinal epithelium. The focal coagulation necrosis produced by TFE predisposes the animals to lethal enteritis and systemic bacteremia.

2,2,2-Trifluoroethanol toxicity in hamsters (Mesocricetus auratus)

As part of an effort to further elucidate the mechanism whereby fluorinated ether anesthetics express their various toxic effects, Golden Syrian hamsters were utilized to determine acute and subchronic toxicities of the anesthetic metabolite 2,2,2-trifluoroethanol (TFE). The major lesion observed with the TFE (0.25 g/kg ip) was coagulation necrosis characterized by nuclear pyknosis in epithelial cells of intestinal villi, the deeper portion of gastric mucosae, lymphoid organs such as thymus, spleen and mesenteric lymph nodules and brain. Hepatocyte hypertrophy with diffuse vacuolar degeneration was also found. Lungs had a characteristic focal terminal bronchiolar epithelial hyperplasia with discrete mucous metaplasia in the terminal bronchioles. In subchronic studies, hamsters were injected with sublethal doses of TFE (0.20 g/kg once per week for 5 weeks). The major lesions observed were severe hepatocyte hyperplasia and hypertrophy with fatty degeneration, necrosis of hair germinal matrix, urinary bladder transitional epithelial cellular hypertrophy, and hyperplasia with vacuolar degeneration and submucosal edema. Ultrastructural studies of acutely treated animals indicate that fat vacuoles formed within the hepatic endoplasmic reticulum characterized by lamellar bodies forming multiple myelin figures within the fat vacuoles. Hepatic cytochrome P-450 concentrations measured as a possible index of endoplasmic reticulum damage, failed to reveal any significant differences between the treated and non-treated hamsters.

Enzymatic activation of chemicals to toxic metabolites

A variety of enzymes function in the oxygenation, oxidation-reduction, conjugation, and hydrolysis of drugs and other foreign chemicals. Often these enzymes detoxicate chemicals to prevent detrimental effects. In this review we will, however, concentrate on cases in which metabolism activates chemicals to reactive species which cause cellular damage. Particular attention will be given to mixed-function oxidases, which carry out a variety of oxygenations, as well as other reactions. (We will focus on cellular toxicity as opposed to initiation of tumorigenesis in this review.) In many cases, considerable circumstantial evidence exists linking these enzymes to enhanced toxicity of chemicals, although causal relationships have seldom been demonstrated. Further, in very few cases is the explicit cause of toxicity known. Modification of critical protein residues is suspected, although oxidative stress may also be involved in some cases. We discuss general aspects of mechanisms of toxic action, briefly list all cases in which metabolism is suspected to play a role in enhancing toxicity, and review a few examples in detail where substantial chemical and enzymatic information is available. The latter instances would involve knowledge of the enzymes involved, chemical evidence on the structures of the reactive metabolites, identification of adducts, and some inference into the biological processes which are effected to elicit toxicity. We consider, in this regard, vinyl halides (which have been a focus in our own laboratory), acetaminophen, pyrrolizidine alkaloids, and fluoroxene.

Interactions of CNS drugs--hypnotics and sedatives

The physicochemical properties of the barbiturates and a brief review of microsomal enzyme induction introduces this literature review of the interactions of sedative and hypnotic drugs. Food has been shown to delay absorption of barbiturates; barbiturates, in turn, may interfere with the absorption of griseofulvin, dicumarol, and folic acid. Barbiturate-produced enzyme induction may result in interactions with the oral anticoagulants, the anticonvulsants, vitamin D, bilirubin, digitoxin, doxycycline, and perhaps other drugs. The problem of additive central nervous system depression and the relative lack of documented evidence is considered. Finally, the interactions of nonbarbiturate hypnotics, such as glutethimide, chloral hydrate, and others are reviewed.

The biochemical basis of anesthetic toxicity

The inhalational anesthetics reversibly inhibit mitochondrial electron transport from NADH-linded substrates at the level of the enzyme NADH-dehydrogenase. The effect of this inhibition on ATP production is probably not the basis of the anesthetic state, as the level of high-energy phosphate in the brain does not decrease during anesthesia. Anesthetics, therefore, interfere with brain energy untilization, in addition to brain energy production. Inhibition by anesthetics of mitochondrial calcium uptake, which results from the inhibition of electron transport, may be an important anesthetic effect if it raises the intracellular calcium level. Other areas of investigation which have not been discussed here include the effects of anesthetics on glycolytic and other enzyme systems, ion fluxes, neurotransmitter synthesis and release, and on the structure of natural and artificial membranes. It is now appreciated that most of the inhalational anesthetics are metabolized by the endoplasmic reticulum of hepatocytes. The biotransformation of several anesthetics can be increased by drugs which induce hepatic microsomal enzymes. The organ toxicities of chloroform, trichloroethylene, fluroxene, methoxyflurane, and possibly of halothane and enflurane are related to their intermediary or final metabolites. It is of anesthetic drugs for an individual patient.

Anaesthesia and the epileptic pateint. A review

A review is presented of some of the problems that may arise in association with anaesthesia for epileptic patients. There is the possibility of precipitating anticonvulsant drug toxicity. Numerous drug interactions are possible with some anticonvulsant agents, such as phenobarbitone and phenytoin, which affect hepatic microsomal enzyme systems. There is the risk of convulsions occurring in susceptible patients following the use of the new anaesthetic agents which are capable of inducing CNS excitability.