The role of para-aminophenol in acetaminophen-induced methemoglobinemia in dogs and cats

Emergency treatment with intravenous infusion of methylene blue followed by oral administration in a cat presented with severe recurrent methemoglobinemia

OBJECTIVE

To describe the use of IV infusion followed by oral administration of methylene blue (MB) to successfully treat recurrent methemoglobinemia (MetHb) in a young cat.

CASE SUMMARY

A 6-month-old male Ragdoll cat presented with recurrent episodes of severe MetHb and was successfully managed with IV infusion of MB followed by a course of oral MB. Although the definitive cause of the patient's MetHb remains unknown, the cat made a full recovery following treatment without developing any significant side effects secondary to therapy and at the time of writing not had any further recurrences. Follow-up at 6 months found the patient in good health and without any long-term consequences.

NEW INFORMATION PROVIDED

To the authors' knowledge, this is the first report of a cat presented with severe MetHb quantitatively assessed via co-oximetry and successfully treated with both IV and oral administration of MB.

Preclinical safety assessment of JNJ-10450232 (NTM-006), a structural analog of acetaminophen, that does not cause hepatotoxicity at supratherapeutic doses

JNJ-10450232 (NTM-006) is a new molecular entity that is structurally related to acetaminophen. A comprehensive non-clinical safety program was conducted to support first-in-human and clinical efficacy studies based on preclinical data suggesting that the compound has comparable or enhanced antinociceptive and antipyretic efficacy without causing hepatotoxicity at supratherapeutic doses. No hepatic toxicity was noted in a mouse model sensitive to acetaminophen hepatotoxicity or in rats, dogs, and non-human primates in 28-day repeat dose toxicity studies at and above doses/exposures at which acetaminophen is known to cause hepatotoxicity. In the 28-day toxicity studies, all treatment-related findings were monitorable and reversible. Methemoglobinemia, which was observed in dogs and to a lesser extent in rats, is also observed with acetaminophen. This finding is considered not relevant to humans due to species differences in metabolism. Thyroid hypertrophy and hyperplasia were also observed in dogs and were shown to be a consequence of a species-specific UGT induction also demonstrated with increased thyroid hormone metabolism. Indirect bilirubin elevation was observed in rats as a result of UGT1A1 Inhibition. JNJ-10450232 (NTM-006) had no toxicologically relevant findings in safety pharmacology or genotoxicity studies. Together, these data supported progressing into safety and efficacy studies in humans.

Model of Acute Liver Failure in an Isolated Perfused Porcine Liver-Challenges and Lessons Learned

Acute liver failure (ALF) is a rare but devastating disease associated with substantial morbidity and a mortality rate of almost 45%. Medical treatments, apart from supportive care, are limited and liver transplantation may be the only rescue option. Large animal models, which most closely represent human disease, can be logistically and technically cumbersome, expensive and pose ethical challenges. The development of isolated organ perfusion technologies, originally intended for preservation before transplantation, offers a new platform for experimental models of liver disease, such as ALF. In this study, female domestic swine underwent hepatectomy, followed by perfusion of the isolated liver on a normothermic machine perfusion device. Five control livers were perfused for 24 h at 37 °C, while receiving supplemental oxygen and nutrition. Six livers received toxic doses of acetaminophen given over 12 h, titrated to methemoglobin levels. Perfusate was sampled every 4 h for measurement of biochemical markers of injury (e.g., aspartate aminotransferase [AST], alanine aminotransferase [ALT]). Liver biopsies were taken at the beginning, middle, and end of perfusion for histological assessment. Acetaminophen-treated livers received a median dose of 8.93 g (8.21–9.75 g) of acetaminophen, achieving a peak acetaminophen level of 3780 µmol/L (3189–3913 µmol/L). Peak values of ALT (76 vs. 105 U/L; p = 0.429) and AST (3576 vs. 4712 U/L; p = 0.429) were not significantly different between groups. However, by the end of perfusion, histology scores were significantly worse in the acetaminophen treated group (p = 0.016). All acetaminophen treated livers developed significant methemoglobinemia, with a peak methemoglobin level of 19.3%, compared to 2.0% for control livers (p = 0.004). The development of a model of ALF in the ex vivo setting was confounded by the development of toxic methemoglobinemia. Further attempts using alternative agents or dosing strategies may be warranted to explore this setting as a model of liver disease.

Metabolism and Effects on Endogenous Metabolism of Paracetamol (Acetaminophen) in a Porcine Model of Liver Failure

The metabolic fate, toxicity, and effects on endogenous metabolism of paracetamol (acetaminophen, APAP) in 22 female Landrace cross large white pigs were evaluated in a model of acute liver failure (ALF). Anesthetized pigs were initially dosed at 250 mg/kg via an oroduodenal tube with APAP serum concentrations maintained above 300 mg/l using maintenance doses of 0.5–4 g/h until ALF. Studies were undertaken to determine both the metabolic fate of APAP and its effects on the endogenous metabolic phenotype of ALF in using ¹H NMR spectroscopy. Increased concentrations of citrate combined with pre-ALF increases in circulating lactate, pyruvate, and alanine in plasma suggest mitochondrial dysfunction and a switch in hepatic energy metabolism to glycolysis in response to APAP treatment. A specific liquid chromatography-tandem mass spectrometry assay was used to quantify APAP and metabolites. The major circulating and urinary metabolite of APAP was the phenolic glucuronide (APAP-G), followed by p-aminophenol glucuronide (PAP-G) formed from N-deacetylated APAP. The PAP produced by N-deacetylation was the likely cause of the methemoglobinemia and kidney toxicity observed in this, and previous, studies in the pig. The phenolic sulfate of APAP, and the glutathione-derived metabolites of the drug were only found as minor components (with the cysteinyl conjugate detected but not the mercapturate). Given its low sulfation, combined with significant capacity for N-deacetylation the pig may represent a poor translational model for toxicology studies for compounds undergoing significant metabolism by sulfation, or which contain amide bonds which when hydrolyzed to unmask an aniline lead to toxicity. However, the pig may provide a useful model where extensive amide hydrolysis is seen for drugs or environmental chemicals in humans, but not in, eg, the rat and dog which are the preclinical species normally employed for safety assessment.

Metabolism and pharmacokinetics of pharmaceuticals in cats (Felix sylvestris catus) and implications for the risk assessment of feed additives and contaminants

In animal health risk assessment, hazard characterisation of feed additives has been often using the default uncertainty factor (UF) of 100 to translate a no-observed-adverse-effect level in test species (rat, mouse, dog, rabbit) to a 'safe' level of chronic exposure in farm and companion animal species. Historically, both 10-fold factors have been further divided to include chemical-specific data in both dimensions when available. For cats (Felis Sylvestris catus), an extra default UF of 5 is applied due to the species' deficiency in particularly glucuronidation and glycine conjugation. This paper aims to assess the scientific basis and validity of the UF for inter-species differences in kinetics (4.0) and the extra UF applied for cats through a comparison of kinetic parameters between rats and cats for 30 substrates of phase I and phase II metabolism. When the parent compound undergoes glucuronidation the default factor of 4.0 is exceeded, with exceptions for zidovudine and S-carprofen. Compounds that were mainly renally excreted did not exceed the 4.0-fold default. Mixed results were obtained for chemicals which are metabolised by CYP3A in rats. When chemicals were administered intravenously the 4.0-fold default was not exceeded with the exception of clomipramine, lidocaine and alfentanil. The differences seen after oral administration might be due to differences in first-pass metabolism and bioavailability. Further work is needed to further characterise phase I, phase II enzymes and transporters in cats to support the development of databases and in silico models to support hazard characterisation of chemicals particularly for feed additives.

Systematic Review of Methemoglobinemia in Acetaminophen Poisoning

BACKGROUND

Acetaminophen (N-acetyl-para-aminophenol, paracetamol, (APAP) toxicity is one of the commonly encountered poisonings by emergency physicians. Methemoglobinemia is an uncommon association and rarely seen in APAP poisoning.

METHODS

Retrospective analysis of all the published reports on APAP induced methemoglobinemia from 1968 to 2019.

RESULTS

In total there were 14 cases with 9 females and 6 males. The median age of the study cohort was 59 years. The most common presenting feature was altered mentation (9 patients) followed by cyanosis (3 patients). The intent of consumption was therapeutic (7 cases) versus suicidal (5 cases) attempt.In most cases, the dose of APAP consumption was not known. Aspirin, sulfasalazine, benzocaine spray, nitrate preservative, contaminated water, detergents, etc. where the other agents consumed by the patients in addition to APAP before developing methemoglobinemia. The median MethHb level of the study cohort was 15.85% Patients were treated with NAC, hemodialysis, methylene blue, and ascorbic acid and CRRT in various combinations. Full recovery was seen in 9 patients while 4 patients died.

CONCLUSION

APAP toxicity is a well-known and common entity with multiple sequelae that presents with a variable spectrum of mild to fulminant multiorgan failure. Awareness of non-classical presentations like methemoglobinemia is essential to ensure timely intervention.

Lethal methemoglobinemia in the invasive brown treesnake after acetaminophen ingestion

The invasive brown treesnake (Boiga irregularis) has extirpated much of Guam's native birdlife and poses significant threats to other parts of the western Pacific. Acetaminophen (APAP) is a proven lethal oral toxicant in reptiles but the physiological mechanism is unknown. The effects of a lethal APAP oral dose on methemoglobin (MetHb, non-oxygen carrying form) levels and other blood parameters were examined in brown treesnakes. Co-oximetry was used to measure MetHb (%) and other hemoglobin species. Assessment of red blood cell integrity, white blood cell differential counts, and plasma biochemical analyses were conducted to evaluate tissue damage, stress, and liver function. Changes in oxygen carrying capacity were noted in APAP-treated snakes indicated by a 50-60% increase in methemoglobin levels and a 40% decrease in oxyhemoglobin (oxygen-carrying form) levels compared to controls. APAP-treated snakes had decreased lymphocyte and increased monocyte counts while also having increased levels of blood analytes associate with impaired liver function and muscle damage. The proximate cause of death in APAP-treated snakes was likely acute methemoglobinemia and respiratory failure due to severe hypoxia with no observed signs of distress or pain. An orally-ingested lethal dose of APAP appears to be a humane method for lethal control of this species.

Antiinflammatory Drugs

This article reviews the mechanisms of action, clinical use, and recent scientific evidence for the use of nonsteroidal antiinflammatory drugs, grapiprant, acetaminophen (paracetamol), metamizole (dipyrone), and corticosteroids in pain management. The discussion is presented with an emphasis on the treatment of acute pain.

Methemoglobinemia associated with massive acetaminophen ingestion: a case series

Background: Acetaminophen is a common pharmaceutical ingestion reported to US poison centers. In overdose, toxic metabolites are known to cause hepato- and nephrotoxicity. While G6PD deficiency may be a risk factor for methemoglobin production in the setting of acetaminophen overdose, it is rarely reported in patients who do not have this condition.Methods: We present two cases of methemoglobinemia following massive acetaminophen ingestion with no known history of G6PD deficiency or other substances known to induce methemoglobinemia. The two cases had peak methemoglobin measurements of 32% and 12% respectively, and both were treated with methylene blue.Discussion: A number of mechanisms may be involved in production of methemoglobin in the setting of massive acetaminophen ingestion including NAPQI-induced oxidation, depletion of glutathione stores, and production of oxidant-metabolites including paraaminophenol. While it is unlikely that the majority of acetaminophen overdoses result in any clinically significant methemoglobinemia, massive acetaminophen overdose may be complicated by development of methemoglobinemia.Conclusion: Physicians should be aware of the possibility that massive acetaminophen ingestion may be complicated by methemoglobinemia in rare instances. Further studies should aim to characterize the metabolic pathways leading to possible methemoglobinemia in humans after large acetaminophen ingestions.

Antioxidant supplementation during illness in dogs: effect on oxidative stress and outcome, an exploratory study

OBJECTIVES

To assess whether combination antioxidant supplementation for 30 days in systemically ill dogs alters antioxidant status, degree of lipid peroxidation, clinical score and survival.

MATERIALS AND METHODS

Forty client-owned systemically-ill hospitalised dogs were eligible for inclusion. Dogs were randomised to no supplementation (NS; n=19) or supplementation with N-acetylcysteine/S-adenosylmethionine/silybin and vitamin E (AS; n=20) for 30 days. Clinical score and oxidative biomarkers including glutathione, cysteine, vitamin E, selenium and urine isoprostanes/creatinine (F₂ -IsoPs/Cr) were determined on days 0 and 30. Glutathione, cysteine, vitamin E and urine F₂ -IsoPs/Cr were quantified by high-performance liquid chromatography, and selenium concentrations determined using atomic absorption spectroscopy.

RESULTS

Thirty-two dogs completed the study (NS, n=16; AS, n=16). Vitamin E concentrations were significantly greater in the supplemented compared to the non-supplemented group. No other markers of oxidative stress significantly changed with supplementation. There was no difference in Day 30 clinical scores or survival between the two groups.

CLINICAL SIGNIFICANCE

In this population of systemically-ill hospitalised dogs, combination antioxidant supplementation did not alter redox state or clinical outcome.

Feline non-regenerative anemia: Diagnostic and treatment recommendations

PRACTICAL RELEVANCE

Non-regenerative anemia, or anemia with reticulocytopenia, is a daily diagnosis in feline practice.

CLINICAL CHALLENGES

The disease processes underlying non-regenerative anemia are many and diverse. A major diagnostic evaluation may be required to correctly diagnose and treat the underlying cause.

AUDIENCE

All veterinarians caring for cats will face the diagnostic and therapeutic challenge of non-regenerative anemia. Readers will benefit from the review of diagnostic testing and therapeutic options for non-regenerative anemia.

EVIDENCE BASE

This review summarizes the currently available literature informing diagnostic and treatment recommendations related to non-regenerative anemia. The evidence available to support the recommendations in this review is graded as low and includes predominantly expert opinion, case reports and cases series, on which the authors' interpretation/consensus is based.

Phylogenetic origins for severe acetaminophen toxicity in snake species compared to other vertebrate taxa

While it has been known for a while that some snake species are extremely sensitive to acetaminophen, the underlying mechanism for this toxicity has not been reported. To investigate if essential detoxification enzymes are missing in snake species that are responsible for biotransformation of acetaminophen in other vertebrate species, livers were collected from a variety of snake species, together with samples from alligator, snapping turtle, cat, rat, and cattle. Subcellular fractions were analyzed for enzymatic activities of phenol-type sulfotransferase and UDP‑glucuronosyltransferase, total glutathione S‑transferase, and N‑acetyltransferase. The results showed that none of the snake species, together with the cat samples, had any phenol-type glucuronidation activity, and that this activity was much lower in alligator and turtle samples than in the mammalian species. Combined with the lack of N‑acetyltransferase activity in snakes and cats, this would explain the accumulation of the aminophenol metabolite, which induces methemoglobinemia and subsequent suffocation of snakes and cats after acetaminophen exposure. While previous investigations have concluded that in cats the gene for the phenol-type glucuronosyltransferase isoform has turned into a pseudogene because of several point mutations, evaluation of genomic information for snake species revealed that they have only 2 genes that may code for glucuronosyltransferase isoforms. Similarity of these genes with mammalian genes is <50%, and suggests that the expressed enzymes may act on other types of substrates than aromatic amines. This indicates that the extreme sensitivity for acetaminophen in snakes is based on a different phylogenetic origin than the sensitivity observed in cats.

Orchitis and balanoposthitis in a dog with Leptospira interrogans serovar Canicola in Southern California

Leptospirosis is a disease caused by bacteria Leptospira. It can infect multiple species of mammals, including humans, dogs, rats, mice, raccoons, skunks, opossums, cows and pigs. Once infected, mammals may present with a variety of clinical manifestations. While the classical presentation of the disease is easily recognised by experienced clinicians practising in endemic regions, atypical systemic manifestations can be missed. In this case report, we describe the atypical manifestations of orchitis and balanoposthitis in a five-year-old male intact dog from Los Angeles County, California with confirmed leptospirosis. The dog was infected with serovar Canicola, which is uncommon for this region. Awareness of these atypical manifestations would hopefully guide clinicians towards early diagnosis.

The effect of acetaminophen on ubiquitin homeostasis in Saccharomyces cerevisiae

Acetaminophen (APAP), although considered a safe drug, is one of the major causes of acute liver failure by overdose, and therapeutic chronic use can cause serious health problems. Although the reactive APAP metabolite N-acetyl-p-benzoquinoneimine (NAPQI) is clearly linked to liver toxicity, toxicity of APAP is also found without drug metabolism of APAP to NAPQI. To get more insight into mechanisms of APAP toxicity, a genome-wide screen in Saccharomyces cerevisiae for APAP-resistant deletion strains was performed. In this screen we identified genes related to the DNA damage response. Next, we investigated the link between genotype and APAP-induced toxicity or resistance by performing a more detailed screen with a library containing mutants of 1522 genes related to nuclear processes, like DNA repair and chromatin remodelling. We identified 233 strains that had an altered growth rate relative to wild type, of which 107 showed increased resistance to APAP and 126 showed increased sensitivity. Gene Ontology analysis identified ubiquitin homeostasis, regulation of transcription of RNA polymerase II genes, and the mitochondria-to-nucleus signalling pathway to be associated with APAP resistance, while histone exchange and modification, and vesicular transport were connected to APAP sensitivity. Indeed, we observed a link between ubiquitin levels and APAP resistance, whereby ubiquitin deficiency conferred resistance to APAP toxicity while ubiquitin overexpression resulted in sensitivity. The toxicity profile of various chemicals, APAP, and its positional isomer AMAP on a series of deletion strains with ubiquitin deficiency showed a unique resistance pattern for APAP. Furthermore, exposure to APAP increased the level of free ubiquitin and influenced the ubiquitination of proteins. Together, these results uncover a role for ubiquitin homeostasis in APAP-induced toxicity.

Veterinary Forensic Toxicology

Veterinary pathologists working in diagnostic laboratories are sometimes presented with cases involving animal poisonings that become the object of criminal or civil litigation. Forensic veterinary toxicology cases can include cases involving animal cruelty (malicious poisoning), regulatory issues (eg, contamination of the food supply), insurance litigation, or poisoning of wildlife. An understanding of the appropriate approach to these types of cases, including proper sample collection, handling, and transport, is essential so that chain of custody rules are followed and proper samples are obtained for toxicological analysis. Consultation with veterinary toxicologists at the diagnostic laboratory that will be processing the samples before, during, and after the forensic necropsy can help to ensure that the analytical tests performed are appropriate for the circumstances and findings surrounding the individual case.

[Association of benzocaine and paracetamol with neonatal-acquired methemoglobinemia]

BACKGROUND

Drug-induced acquired methemoglobinemia in the newborn is a rare event; however, when it develops, early diagnosis and proper treatment become paramount because it can evolve rapidly into a particularly serious disease causing permanent brain damage or death.

CASE REPORT

We report a unique case of severe methemoglobinemia that developed in a newborn associated with a minimal application of a benzocaine healing cream to an anal surgical wound while on acetaminophen. In addition to benzocaine as the primary cause in this case, we raise the possibility that acetaminophen-a mild oxidant-increased the susceptibility of the patient to benzocaine, leading to severe clinical methemoglobinemia based on the known immaturity of the enzymatic systems involved in caines and acetaminophen clearance in the newborn. Treatment of methemoglobinemia is reviewed.

CONCLUSIONS

Methemoglobinemia is a serious condition that can be easily induced by the use of oxidant medications in the newborn like local anesthetics. The possibility of unexpected drug to drug interactions, particularly between commonly used medications such as acetaminophen with other methemoglobin-causing agents, must always be kept in mind. Because of the possible deleterious consequences, mandatory labelling of caine-containing local anesthetic creams, gels and sprays with a warning for the likelihood of causing severe methemoglobinemia in children is recommended. Also, prohibiting their use in the newborn becomes mandatory.

A Cytochrome P450-Independent Mechanism of Acetaminophen-Induced Injury in Cultured Mouse Hepatocytes

Mouse hepatic parenchymal cells (HPCs) have become the most frequently used in vitro model to study mechanisms of acetaminophen (APAP)-induced hepatotoxicity. It is universally accepted that APAP hepatocellular injury requires bioactivation by cytochromes P450 (P450s), but this remains unproven in primary mouse HPCs in vitro, especially over the wide range of concentrations that have been employed in published reports. The aim of this work was to test the hypothesis that APAP-induced hepatocellular death in vitro depends solely on P450s. We evaluated APAP cytotoxicity and APAP-protein adducts (a biomarker of metabolic bioactivation by P450) using primary mouse HPCs in the presence and absence of a broad-spectrum inhibitor of P450s, 1-aminobenzotriazole (1-ABT). 1-ABT abolished formation of APAP-protein adducts at all concentrations of APAP (0-14 mM), but eliminated cytotoxicity only at small concentrations (≦5 mM), indicating the presence of a P450-independent mechanism at larger APAP concentrations. P450-independent cell death was delayed in onset relative to toxicity observed at smaller concentrations. p-Aminophenol was detected in primary mouse HPCs exposed to large concentrations of APAP, and a deacetylase inhibitor [bis (4-nitrophenyl) phosphate (BNPP)] significantly reduced cytotoxicity. In conclusion, APAP hepatocellular injury in vitro occurs by at least two mechanisms, a P450-dependent mechanism that operates at concentrations of APAP ≦ 5 mM and a P450-independent mechanism that predominates at larger concentrations and is slower in onset. p-Aminophenol most likely contributes to the latter mechanism. These findings should be considered in interpreting results from APAP cytotoxicity studies in vitro and in selecting APAP concentrations for use in such studies.

Adjunctive, pain-modifying, analgesic drugs

Outside the realm of nonsteroidal antiinflammatory drug(NSAID) and opioid exist a broad range of medications that exert an analgesic effect, or otherwise modify and protect against pain, by manipulating various targets along the nociceptive pathway. Strength of evidence for dogs and cats can vary widely, and this article will review the available literature that may guide clinical usage in these species.

Feline drug metabolism and disposition: pharmacokinetic evidence for species differences and molecular mechanisms

Although it is widely appreciated that cats respond differently to certain drugs compared with other companion animal species, the causes of these differences are poorly understood. This article evaluates published evidence for altered drug effects in cats, focusing on pharmacokinetic differences between cats, dogs, and humans, and the molecular mechanisms underlying these differences. More work is needed to better understand drug metabolism and disposition differences in cats, thereby enabling more rational prescribing of existing medications, and the development of safer drugs for this species.

Comparison of NADH-dependent cytochrome b5 reductase activity and in vitro methemoglobin induction by sodium nitrite in Oncorhynchus mykiss, Salmo salar, and Salvelinus fontinalis

Methemoglobin is hemoglobin containing ferric iron. Methemoglobin cannot bind to oxygen and at high concentrations causes tissue hypoxia. Brook trout (Salvelinus fontinalis) develop significantly greater methemoglobinemia than Atlantic salmon (Salmo salar) or rainbow trout (Oncorhynchus mykiss) following general anesthesia with benzocaine or tricaine methanesulfonate. The objective of this study was to compare the activity of the major methemoglobin reducing enzyme, NADH-dependent cytochrome b5 reductase (CB5R), in brook trout erythrocytes to the activity of CB5R in Atlantic salmon and rainbow trout erythrocytes. Methemoglobin levels were compared using co-oximetry following in vitro incubation of erythrocytes with sodium nitrite (NaNO(2)). The CB5R activity was measured using a ferricyanide assay. There was significantly greater methemoglobin at time 0 in brook trout erythrocytes than in rainbow trout or Atlantic salmon erythrocytes (2.79 ± 0.29 %, 2.19 ± 0.23 %, 2.08 ± 0.14 %), (P < 0.001). There was significantly greater methemoglobin induction by NaNO(2) in brook trout erythrocytes (33.14 ± 3.32 %) than in rainbow trout or Atlantic salmon erythrocytes (28.73 ± 2.92 % and 24.85 ± 1.40 %, respectively), (P < 0.001). The CB5R activity was significantly less in brook trout erythrocytes (median of 3.05 μmol/min/μl) than in rainbow trout erythrocytes (median of 6.73 μmol/min/μl). The CB5R activity in Atlantic salmon erythrocytes (median 4.09 μmol/min/μl) was not significantly different than in brook or rainbow trout erythrocytes. Total methemoglobin at any one time is a balance between induction by oxidants and reduction by antioxidants. Lower CB5R activity in brook trout erythrocytes may contribute to a species-specific sensitivity to methemoglobin induction; however, there are likely additional factors.

A reproducible, clinically relevant, intensively managed, pig model of acute liver failure for testing of therapies aimed to prolong survival

BACKGROUND

A clinically relevant, translational large animal model of acute liver failure (ALF) is required for testing of novel therapies to prolong survival in acute liver failure, to permit spontaneous liver recovery or to act as a bridge to transplantation.

AIMS

The aim was to establish a pig model of acetaminophen-induced ALF that mimics the human clinical syndrome, is managed as in a human intensive care unit and has a predictable survival time.

METHODS

Nine female pigs were anaesthetised and instrumented for continuous intensive care monitoring and management using: target-driven protocols for treatment of cardiovascular collapse, metabolic acidosis and electrolyte abnormalities; intermittent positive pressure ventilation; and continuous renal replacement therapy. Six animals were induced to ALF with acetaminophen (paracetamol). Three animals acted as controls.

RESULTS

Irreversible acute liver failure, defined as rise in prothrombin time >3 times normal, occurred 19.3 ± 1.8 h after the onset of acetaminophen administration. Death occurred predictably 12.6 ± 2.7 h thereafter, with acute hepatocellular necrosis in all animals. Clinical progression of liver failure mimicked the human condition including development of coagulopathy, intracranial hypertension, hyperammonaemia, cardiovascular collapse, elevation in creatinine, metabolic acidosis and hyperlactataemia. In addition, cardiovascular monitoring clearly demonstrated progressive cardiac dysfunction in ALF.

CONCLUSIONS

A reproducible, clinically relevant, intensively managed, large animal model of acute liver failure, with death as a result of multi-organ failure, has been successfully validated for translational studies of disease progression and therapies designed to prolong survival in man.

Influence of sewage and pharmaceuticals on soil microbial function

Although sewage effluent application to land is a common approach to recycle water and provide nutrients to plants, bioactive pharmaceuticals contained in sewage may change soil quality by affecting soil microbial communities. Establishing causal effects, however, is difficult, because trace levels of pharmaceuticals are confounded with other effluent constituents. Therefore, two originally similar soil microbial communities, one irrigated in situ with sewage effluent for 12 years and another nonirrigated, were exposed to high levels of acetaminophen, aspirin, carbamazepine, chlorpromazine, and tetracycline. The objectives of the current study were to determine the influence of high levels of pharmaceuticals on several soil microbial properties, the effect that prolonged effluent irrigation with ambient levels of pharmaceuticals had on soil microbial function, and how this effect would change in response to pharmaceutical exposure. Several pharmaceuticals, at high exposure levels, imposed stress on the soil microbial community as judged by increased CO(2) respiration, decreased biomass carbon, and altered substrate utilization affinities. Prolonged effluent irrigation, which altered the genetic fingerprint of the microbial community, also mitigated the response that exposure to pharmaceuticals had on the microbial community and enabled degradation of the antimicrobial salicylic acid after aspirin exposure. In conclusion, prolonged irrigation with sewage effluent containing pharmaceuticals at ambient levels influenced the microbial community so that they were able to better cope with sudden exposure to high levels of pharmaceuticals.