Antidote review: fomepizole for methanol poisoning

Anticancer Properties of Asian Water Monitor Lizard (Varanus salvator), Python (Malayopython reticulatus) and Tortoise (Cuora kamaroma amboinensis)

BACKGROUND

Cancer contributes to significant morbidity and mortality despite advances in treatment and supportive care. There is a need for the identification of effective anticancer agents. Reptiles such as tortoise, python, and water monitor lizards are exposed to heavy metals, tolerate high levels of radiation, feed on rotten/germ-infested feed, thrive in unsanitary habitat and yet have prolonged lifespans. Such species are rarely reported to develop cancer, suggesting the presence of anticancer molecules/mechanisms.

METHODS

Here, we tested effects from sera of Asian water monitor lizard (Varanus salvator), python (Malayopython reticulatus) and tortoise (Cuora kamaroma amboinensis) against cancer cells. Sera were collected and cytotoxicity assays were performed using prostate cancer cells (PC3), Henrietta Lacks cervical adenocarcinoma cells (HeLa) and human breast adenocarcinoma cells (MCF7), as well as human keratinized skin cells (Hacat), by measuring lactate dehydrogenase release as an indicator for cell death. Growth inhibition assays were performed to determine the effects on cancer cell proliferation. Liquid chromatography mass spectrometry was performed for molecular identification.

RESULTS

The findings revealed that reptilian sera, but not bovine serum, abolished viability of Hela, PC3 and MCF7 cells. Samples were subjected to liquid chromatography mass spectrometry, which detected 57 molecules from V. salvator, 81 molecules from Malayopython reticulatus and 33 molecules from C. kamaroma amboinensis and putatively identified 9 molecules from V. salvator, 20 molecules from Malayopython reticulatus and 9 molecules from C. kamaroma amboinensis when matched against METLIN database. Based on peptide amino acid composition, binary profile, dipeptide composition and pseudo-amino acid composition, 123 potential Anticancer Peptides (ACPs) were identified from 883 peptides from V. salvator, 306 potential ACPs from 1074 peptides from Malayopython reticulatus and 235 potential ACPs from 885 peptides from C. kamaroma amboinensis.

CONCLUSION

To our knowledge, for the first time, we reported comprehensive analyses of selected reptiles' sera using liquid chromatography mass spectrometry, leading to the identification of potentially novel anticancer agents. We hope that the discovery of molecules from these animals will pave the way for the rational development of new anticancer agents.

Bibliometric profile of the global scientific research on methanol poisoning (1902-2012)

BACKGROUND

Methanol poisoning is on the rise and has been associated with high morbidity and mortality; it has resulted in growing research in the field of toxicology. The aim of this study was to reveal underlying patterns in scientific outputs related to methanol poisoning at the global level by evaluating different bibliometric indices.

METHODS

We searched for publications that contained specific words regarding methanol poisoning in Scopus database.

RESULTS

A total of 912 articles, with 8,317 citations and with an average of 9.1 citations per document, were retrieved on methanol poisoning, and the bulk of the articles were published from the USA (20.9%), followed by Spain (4.4%), Canada (4.3%), India (3.1%), and France (3.0%). The articles were published belonging to 57 countries. No data related to methanol poisoning were published from 155 (73.1%) out of 212 countries. Twenty-one documents (2.3%) were published in Clinical Toxicology, whereas 18 (2.0%) were published in The Lancet.

CONCLUSIONS

Scientific production related to methanol poisoning is increasing. articles have been published in a wide range of journals with a variety of subject areas, most notably clinical toxicology; and the country with the greatest production was the USA.

Protective effects of fomepizole on 2-chloroethanol toxicity

2-Chloroethanol (2-CE) is a widely used industrial solvent. In Taiwan, Taiwanese farmers apply 2-CE on grape-vines to accelerate grape growth, a practice that in some cases have caused poisoning in humans. Thus, there is strong interest in identifying antidotes to 2-CE. This study examines the protective role in 2-CE intoxicated rats. Alcohol dehydrogenase and glutathione were hypothesized to be important in the metabolism of 2-CE. This study used fomepizole, an alcohol dehydrogenase inhibitor, and chemicals that affected glutathione metabolism to study 2-CE toxicity. Notably, fomepizole 5 mg/kg significantly increased median lethal dose (LD50) of 2-CE from 65.1 to 180 mg/kg and reduced the production of a potential toxic metabolite chloroacetaldehyde (CAA) in animal plasma. In contrast, disulfiram (DSF), an aldehyde dehydrogenase inhibitor, increased the toxicity of 2-CE on the lethality in rats. Additional or pretreatment with N-acetylcysteine (NAC) and fomepizole significantly reduced plasma CAA concentrations. Fomepizole also significantly reduced 2-CEinhibited glutathione activity. Otherwise, pretreatment with NAC for 4 days followed by co-treatment with fomepizole significantly decreased formation of the metabolic CAA. These results indicated that its catalytic enzyme might play a vital role during 2-CE intoxication, and the combination of fomepizole and NAC could be a protective role in cases of acute 2-CE intoxication.

Physiology and pharmacology of alcohol: the imidazobenzodiazepine alcohol antagonist site on subtypes of GABAA receptors as an opportunity for drug development?

Alcohol (ethanol, EtOH) has pleiotropic actions and induces a number of acute and long-term effects due to direct actions on alcohol targets, and effects of alcohol metabolites and metabolism. Many detrimental health consequences are due to EtOH metabolism and metabolites, in particular acetaldehyde, whose high reactivity leads to nonspecific chemical modifications of proteins and nucleic acids. Like acetaldehyde, alcohol has been widely considered a nonspecific drug, despite rather persuasive evidence implicating inhibitory GABA(A) receptors (GABA(A)Rs) in acute alcohol actions, for example, a GABA(A)R ligand, the imidazobenzodiazepine Ro15-4513 antagonizes many low-to-moderate dose alcohol actions in mammals. It was therefore rather surprising that abundant types of synaptic GABA(A)Rs are generally not responsive to relevant low concentrations of EtOH. In contrast, delta-subunit-containing GABA(A)Rs and extrasynaptic tonic GABA currents mediated by these receptors are sensitive to alcohol concentrations that are reached in blood and tissues during low-to-moderate alcohol consumption. We recently showed that low-dose alcohol enhancement on highly alcohol-sensitive GABA(A)R subtypes is antagonized by Ro15-4513 in an apparently competitive manner, providing a molecular explanation for behavioural Ro15-4513 alcohol antagonism. The identification of a Ro15-4513/EtOH binding site on unique GABA(A)R subtypes opens the possibility to characterize this alcohol site(s) and screen for compounds that modulate the function of EtOH/Ro15-4513-sensitive GABA(A)Rs. The utility of such drugs might range from novel alcohol antagonists that might be useful in the emergency room, to drugs for the treatment of alcoholism, as well as alcohol-mimetic drugs to harness acute positive effects of alcohol.

The management of severe toxic alcohol ingestions at a tertiary care center after the introduction of fomepizole

INTRODUCTION

Ethylene glycol and methanol ingestions are relatively uncommon but potentially lethal poisonings. Recent trials have demonstrated that fomepizole effectively blocks alcohol dehydrogenase (ADH) in toxic alcohol overdoses, and may eliminate the need for emergent hemodialysis and intensive care unit admission. However, controversy remains in the role of fomepizole in clinical practice. The purpose of this study was to describe the presentation, management and clinical course of toxic alcohol ingestions at a tertiary care referral center after the introduction of fomepizole to hospital formulary.

METHODS

Data was collected on all patents treated for toxic alcohol ingestions for a 1-year period in a tertiary care referral center. Patients who received fomepizole or ethanol infusions, or who underwent hemodialysis were identified by ED, pharmacy, hemodialysis and ICU databases. The patients' medical records were reviewed, and data was recorded on a predetermined computerized data collection form.

RESULTS

Overall, twenty (20) toxic ingestions (14 methanol; 6 ethylene glycol) were identified over the one year period. Fomepizole was used for ADH blockade in 12/20 cases; ETOH infusions in 15/20 cases (combined ETOH and fomepizole use in 7/20). The majority of toxic alcohol exposures were admitted to an intensive care unit (19/20) and received emergent hemodialysis (19/20). All patients were discharged from hospital alive.

CONCLUSIONS

Patients with methanol and ethylene glycol ingestions who presented to our centers had significant toxicity and received both HD and ICU admission. Further research is required to determined if the method of ADH blockade affects the need for hemodialysis or ICU admission in toxic alcohol ingestions.

Methanol mass poisoning in Estonia: outbreak in 154 patients

BACKGROUND

Knowledge of methanol toxicity is based on human data from case series and larger outbreaks. In many of these cases, however, diagnosis was not verified by methanol determinations. We present epidemiological and clinical data from one of the largest methanol outbreaks in which all patients had detectable serum methanol levels.

METHODS

Retrospective case series study of hospital and forensic charts from the five hospitals where patients were treated.

RESULTS

Of the 147 patients admitted with suspected methanol poisoning, the diagnosis was confirmed in 111, of whom 25 (23 %) died. In addition, 43 patients died outside the hospital, giving a total of 154 patients and a death toll of 68 (44 %). Outcome was related to the degree of metabolic acidosis, serum methanol concentration, coma upon admission, and the patient's ability to hyperventilate. Patients were treated with bicarbonate (85 %), ethanol (87 %), hemodialysis (71 %), and mechanical ventilation (61%) according to clinical features and blood gases, since serum methanol concentrations were analyzed retrospectively. Twenty patients (18 %) survived with permanent sequelae, 18 suffered from impaired vision, and 3 developed permanent brain damage.

DISCUSSION

Given limited resources, triage and use age of tertiary care centers allowed a small community hospital to treat a high number of methanol-poisoned patients. Critical resources were ventilators and dialyzing machines, whereas stores of antidote (ethanol) and bicarbonate were sufficient. Many patients were mechanically ventilated by hand and treated with bicarbonate and ethanol during transport to tertiary care centers for hemodialysis.

Compliance With Poison Center Fomepizole Recommendations is Suboptimal in Cases of Toxic Alcohol Poisoning

We sought to examine hospital compliance with poison center antidotal alcohol dehydrogenase inhibition recommendations in cases of ethylene glycol (EG) and methanol (ME) ingestion. A 2-year analysis of all potential EG and ME ingestion cases reported to a regional poison center was conducted. Excluded from analysis were exposures without an ingestion, without a confirmatory EG or ME serum assay, or without complete medical charting. During the study period, 579 EG or ME exposures were reported to the poison center: 133 cases met study eligibility as an ingestion. Of the 133 cases, 102 (77%) had complete data and were included in the analysis. Immediate alcohol dehydrogenase inhibition was recommended by the poison center in 79 of the 102 cases. Fomepizole was recommended in 61/79 (77%); ethanol was recommended as an alternative therapeutic choice in 32/61 (52%) of these cases if fomepizole was not immediately available. Ethanol alone was recommended in 18/79 (23%). Fomepizole was eventually administered in 39/61 (64%) cases where recommended. The mean time to antidote administration was 3 times longer in cases where a choice in antidote was given [57 min (95% confidence interval, 43-70) vs. 146 min (95% confidence interval, 93-200)]. Despite its ease of administration, fomepizole is used less frequently than recommended by poison center staff. Delays to antidote administration occurred more commonly in cases where the poison center gave a choice in antidotal therapy.

Deadly pediatric poisons: nine common agents that kill at low doses

More than 97% of pediatric exposures reported to the AAPCC in 2001 had either no effect or mild clinical effects. Despite the large number of exposures, only 26 of the 1074 reported fatalities occurred in children younger than age 6. These findings reflect the fact that, in contrast to adolescent or adult ingestions, pediatric ingestions are unintentional events secondary to development of exploration behaviors and the tendency to place objects in the mouth. Ingested substances typically are nontoxic or ingested in such small quantities that toxicity would not be expected. As a result, it commonly is believed that ingestion of one or two tablets by a toddler is a benign act and not expected to produce any consequential toxicity. Select agents have the potential to produce profound toxicity and death, however, despite the ingestion of only one or two tablets or sips. Although proven antidotes are a valuable resource, their value is diminished if risk after ingestion is not adequately appreciated and assessed. Future research into low-dose, high-risk exposures should be directed toward further clarification of risk, improvements in overall management strategies,and, perhaps most importantly, prevention of toxic exposure through parental education and appropriate safety legislation.

Toxicology in the critically ill patient

Intoxications present in many forms including: known drug overdose or toxic exposure, illicit drug use, suicide attempt, accidental exposure, and chemical or biological terrorism. A high index of suspicion and familiarity with toxidromes can lead to early diagnosis and intervention in critically ill, poisoned patients. Despite a paucity of evidence-based information on the management of intoxicated patients, a rational and systematic approach can be life saving.