Role of fomepizole in the management of ethylene glycol toxicity

Extracorporeal treatment for ethylene glycol poisoning: systematic review and recommendations from the EXTRIP workgroup

Ethylene glycol (EG) is metabolized into glycolate and oxalate and may cause metabolic acidemia, neurotoxicity, acute kidney injury (AKI), and death. Historically, treatment of EG toxicity included supportive care, correction of acid-base disturbances and antidotes (ethanol or fomepizole), and extracorporeal treatments (ECTRs), such as hemodialysis. With the wider availability of fomepizole, the indications for ECTRs in EG poisoning are debated. We conducted systematic reviews of the literature following published EXTRIP methods to determine the utility of ECTRs in the management of EG toxicity. The quality of the evidence and the strength of recommendations, either strong ("we recommend") or weak/conditional ("we suggest"), were graded according to the GRADE approach. A total of 226 articles met inclusion criteria. EG was assessed as dialyzable by intermittent hemodialysis (level of evidence = B) as was glycolate (Level of evidence = C). Clinical data were available for analysis on 446 patients, in whom overall mortality was 18.7%. In the subgroup of patients with a glycolate concentration ≤ 12 mmol/L (or anion gap ≤ 28 mmol/L), mortality was 3.6%; in this subgroup, outcomes in patients receiving ECTR were not better than in those who did not receive ECTR. The EXTRIP workgroup made the following recommendations for the use of ECTR in addition to supportive care over supportive care alone in the management of EG poisoning (very low quality of evidence for all recommendations): i) Suggest ECTR if fomepizole is used and EG concentration > 50 mmol/L OR osmol gap > 50; or ii) Recommend ECTR if ethanol is used and EG concentration > 50 mmol/L OR osmol gap > 50; or iii) Recommend ECTR if glycolate concentration is > 12 mmol/L or anion gap > 27 mmol/L; or iv) Suggest ECTR if glycolate concentration 8-12 mmol/L or anion gap 23-27 mmol/L; or v) Recommend ECTR if there are severe clinical features (coma, seizures, or AKI). In most settings, the workgroup recommends using intermittent hemodialysis over other ECTRs. If intermittent hemodialysis is not available, CKRT is recommended over other types of ECTR. Cessation of ECTR is recommended once the anion gap is < 18 mmol/L or suggested if EG concentration is < 4 mmol/L. The dosage of antidotes (fomepizole or ethanol) needs to be adjusted during ECTR.

Treating ethylene glycol poisoning with alcohol dehydrogenase inhibition, but without extracorporeal treatments: a systematic review

CONTEXT

Ethylene glycol is metabolized to toxic metabolites that cause acute kidney injury, metabolic acidemia, and death. The treatment of patients with ethylene glycol poisoning includes competitively inhibiting alcohol dehydrogenase with ethanol or fomepizole to prevent the formation of toxic metabolites, and extracorporeal treatments such as hemodialysis to remove ethylene glycol and its metabolites. In the absence of significant metabolic acidemia or kidney injury, it is hypothesized that extracorporeal treatments may be obviated without adverse outcomes to the patient if alcohol dehydrogenase inhibitors are used.

OBJECTIVES

The objectives of this study are to: (1) identify indicators predicting ADH inhibitor failure in patients with ethylene glycol poisoning treated with either ethanol or fomepizole for whom extracorporeal treatment was not performed (aside from rescue therapy, see below) (prognostic study), and (2) validate if the anion gap, shown in a previous study to be the best surrogate for the glycolate concentration, is associated with acute kidney injury and mortality (anion gap study).

METHODS

We conducted a systematic review to identify all reported patients with ethylene glycol poisoning treated without extracorporeal treatments but with either fomepizole (fomepizole monotherapy) or ethanol (ethanol monotherapy). Analyses were performed using both one case per patient and all cases (if multiple events were reported for a single patient). Data were compiled regarding poisoning, biochemistry, and outcomes. Treatment failure was defined as mortality, worsening of acid-base status, extracorporeal treatments used as rescue, or a worsening of kidney or neurological function after alcohol dehydrogenase inhibition was initiated. Also, we performed an analysis of previously described anion gap thresholds to determine if they were associated with outcomes such as acute kidney injury and mortality.

RESULTS

Of 115 publications identified, 96 contained case-level data. A total of 180 cases were identified with ethanol monotherapy, and 231 with fomepizole monotherapy. Therapy failure was noted mostly when marked acidemia and/or acute kidney injury were present prior to therapy, although there were cases of failed ethanol monotherapy with minimal acidemia (suggesting that ethanol dosing and/or monitoring may not have been optimal). Ethylene glycol dose and ethylene glycol concentration were predictive of monotherapy failure for ethanol, but not for fomepizole. In the anion gap study (207 cases), death and progression of acute kidney injury were almost nonexistent when the anion gap was less than 24 mmol/L and mostly observed when the anion gap was greater than 28 mmol/L.

CONCLUSION

This review suggests that in patients with minimal metabolic acidemia (anion gap <28 mmol/L), fomepizole monotherapy without extracorporeal treatments is safe and effective regardless of the ethylene glycol concentration. Treatment failures were observed with ethanol monotherapy which may relate to transient subtherapeutic ethanol concentrations or very high ethylene glycol concentrations. The results are limited by the retrospective nature of the case reports and series reviewed in this study and require prospective validation.

Effect of repeated administration of 4-methylpyrazole on renal function and lipid peroxidation products in rat kidney after ethylene glycol poisoning

Toxic effects of ethylene glycol (EG) and its metabolites are mainly related to metabolic acidosis and kidney damage. EG biotransformation involving CYP2E1 affects the oxidant-antioxidant balance. The study assessed the effect of repeated administration of 4-methylpyrazole (4MP, 15mg/kg b.w. after 2h, followed by 10mg/kg b.w. every 12h) on renal function (creatinine, urea and urinary protein levels) as well as products of kidney's lipid peroxidation (MDA and TBARS levels) in rats poisoned with EG (5745mg/kg b.w.). Serum EG and glycolic acid (GA) concentrations were measured throughout the experiment. Repeated administration of 4MP reduced the rate of EG elimination, extended the period of EG persistence in serum and significantly limited formation of GA. The study showed the temporary intensification of kidney oxidative processes that correlated with changes in kidney function. It was found that the use of 4MP in EG poisoning inhibited its biotransformation to toxic metabolites, but simultaneously intensified oxidative damages in kidneys.

Effect of 4-methylpyrazole on antioxidant enzyme status and lipid peroxidation in the liver of rats after exposure to ethylene glycol and ethyl alcohol

BACKGROUND

The aim of the conducted studies was to evaluate the effect of 4-methylpyrazole, increasingly used in detoxifying treatments after ethylene glycol poisoning, on the activity of some antioxidant enzymes and lipid peroxidation formation in the liver of rats after experimental co-exposure to ethylene glycol and ethyl alcohol.

METHODS

The trials were conducted on adult male Wistar rats. Ethylene glycol (EG) at the dose of 3.83 g/kg bw and ethyl alcohol (EA) at the dose of 1 g/kg bw were administered po, and 4-methylpyrazole (4-MP) at the dose of 0.01 g/kg bw was administered ip. Parameters of antioxidant balance were evaluated in hepatic cytosol, including the activity of the following enzymes: glutathione S-transferase (GST), glutathione reductase (GR), glutathione peroxidase (GPx) and lipid peroxidation level (TBARS).

RESULTS

The results suggest that evaluation of the effects of administrated 4-MP after co-exposure to EG and EA in the liver revealed statistically significant changes on antioxidant enzyme system and malondialdehyde formation.

CONCLUSION

The changes in biomarkers activity indicate a greater production of free radicals which exceeds the capability of antioxidant system, appearing with oxidative stress in the group of animals treated by 4-MP combined with EG and EA.

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.

Ethylene glycol poisoning

Ethylene glycol (EG) can be found in many agents, such as antifreeze. Ingestion of EG may cause serious poisoning. Adults are typically exposed when EG is ingested as a cheap substitute for ethanol or in suicide-attempts. Children may be exposed by accidental ingestion caused by decantation of EG to unlabeled bottles. EG has in itself a low toxicity, but is in vivo broken down to four organic acids: glycoaldehyde, glycolic acid, glyoxylic acid and oxalic acid. The metabolites are cell toxins that cause central nervous system depression, and cardio-pulmonary and renal failure. Glycolic acid causes severe acidosis, and oxalate is precipitated as calcium oxalate in the kidneys and other tissues. We present five case reports of fatal EG-poisoning, and review the literature concerning clinical presentation and diagnosis, pathological findings, treatment and prevention.

4-Hydroxymethyl-1,6,8-trimethylfuro[2,3-h]quinolin-2(1H)-one Induces Mitochondrial Dysfunction and Apoptosis upon Its Intracellular Oxidation

We investigated the mechanism of cell death induced by a furoquinolinone derivative, namely, 4-hydroxymethyl-1,6,8-trimethylfuro[2,3-h]quinolin-2(1H)-one (HOFQ), in the dark. Mitochondrial depolarization was found to be a causative event in HOFQ-induced apoptosis that was blunted either by replacing the 4-hydroxymethyl group with a methyl one, or by 4-methylpyrazole, an inhibitor of alcohol dehydrogenase (ADH). In vitro enzymatic assay demonstrated that HOFQ is a substrate of ADH. In isolated mitochondria HOFQ was without effect, whereas in the presence of ADH and NAD(+) it caused the opening of the permeability transition pore, indicating that HOFQ-oxidized products affect mitochondrial function directly. Finally, an analogue bearing the formyl group at the C-4 position mimicked all the effects exerted by HOFQ. In conclusion, these results suggest that the direct action on mitochondria of HOFQ-oxidized products are responsible for their cytotoxicity, which might be exacerbated, but hardly determined, by photodynamic action and/or binding to DNA.

Fomepizole alone for severe infant ethylene glycol poisoning

OBJECTIVE

To report a case of a massive ingestion of ethylene glycol in an infant successfully treated by fomepizole without hemodialysis.

DESIGN

Descriptive case report.

SETTING

Pediatric intensive care unit.

PATIENT

A 5-mo-old boy who ingested 200 mL of an antifreeze solution.

INTERVENTIONS

Antidotal therapy with a total of seven doses of fomepizole administered intravenously with an interval of 12 hrs (15 mg/kg as loading dose, then 10 mg/kg). Hemodialysis was not performed.

MEASUREMENTS AND MAIN RESULTS

Iterative determination of ethylene glycol concentration was obtained in blood and urine. Kinetics were calculated for ethylene glycol and fomepizole elimination. The infant made a complete recovery with no change in renal function.

CONCLUSIONS

Although not yet approved for this indication in the child, fomepizole seemed safe and effective in a case of severe ethylene glycol poisoning, without the need for hemodialysis.