Fomepizole in ethylene glycol intoxication

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.

A systematic review of ethanol and fomepizole use in toxic alcohol ingestions

Objectives. The optimal antidote for the treatment of ethylene glycol or methanol intoxication is not known. The objective of this systematic review is to describe all available data on the use of ethanol and fomepizole for methanol and ethylene glycol intoxication. Data Source. A systematic search of MEDLINE and EMBASE was conducted. Study Selection. Published studies involving the use of ethanol or fomepizole, or both, in adults who presented within 72 hours of toxic alcohol ingestion were included. Our search yielded a total of 145 studies for our analysis. There were no randomized controlled trials, and no head-to-head trials. Data Extraction. Variables were evaluated for all publications by one independent author using a standardized data collection form. Data Synthesis. 897 patients with toxic alcohol ingestion were identified. 720 (80.3%) were treated with ethanol (505 Me, 215 EG), 146 (16.3%) with fomepizole (81 Me, 65 EG), and 33 (3.7%) with both antidotes (18 Me, 15 EG). Mortality in patients treated with ethanol was 21.8% for Me and 18.1% for EG. In those administered fomepizole, mortality was 17.1% for Me and 4.1% for EG. Adverse events were uncommon. Conclusion. The data supporting the use of one antidote is inconclusive. Further investigation is warranted.

Ethylene glycol poisoning: quintessential clinical toxicology; analytical conundrum

Ethylene glycol poisoning is a medical emergency that presents challenges both for clinicians and clinical laboratories. Untreated, it may cause morbidly or death, but effective therapy is available, if administered timely. However, the diagnosis of ethylene glycol poisoning is not always straightforward. Thus, measurement of serum ethylene glycol, and ideally glycolic acid, its major toxic metabolite in serum, is definitive. Yet measurement of these structurally rather simple compounds is but simple. This review encompasses an assessment of analytical methods for the analytes relevant for the diagnosis and prognosis of ethylene glycol poisoning and of the role of the ethylene glycol metabolites, glycolic and oxalic acids, in its toxicity.

Ethylene glycol ingestion treated only with fomepizole

INTRODUCTION

Ethylene glycol is a widely used chemical that is capable of causing significant injury if ingested. Treatment for ethylene glycol poisoning typically includes basic supportive care, alcohol dehydrogenase inhibition, and hemodialysis. Recent data have suggested that hemodialysis may not be necessary for cases of ethylene glycol poisoning that can be treated with fomepizole as blocking therapy before acidosis or renal dysfunction develops.

CASE REPORT

A 33-year-old man presented to the emergency department 1 hour after drinking approximately 1/2 gallon of ethylene glycol antifreeze and an unknown quantity of beer. On arrival he was mildly inebriated but otherwise displayed no other features of ethylene glycol poisoning. Fomepizole therapy was initiated and initial laboratory studies later revealed an osmol gap of 157 mOsm and an ethylene glycol concentration of 706 mg/dL. Nephrology and toxicology services were consulted. Over the next 3 days, fomepizole therapy was continued while the patient's acid-base status and renal function were closely monitored. No evidence of acid-base abnormalities or renal impairment was ever observed and the patient was discharged to psychiatric care on the fourth hospital day.

DISCUSSION

This report describes the case of a patient who presented soon after a massive ingestion of ethylene glycol with very high serum concentrations. He was successfully treated using fomepizole and basic supportive care. Our patient developed neither renal insufficiency nor metabolic acidosis. His concomitant ethanol consumption, early presentation, and treatment likely contributed to his favorable outcome. This case report underscores the effectiveness of supportive care and fomepizole in the treatment of ethylene glycol poisoning.

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.

Fomepizole as an antidote for ethylene glycol poisoning

OBJECTIVE

To assess the use of fomepizole in the treatment of ethylene glycol poisoning in the absence of hemodialysis.

DATA SOURCES

A MEDLINE search (1966-May 2001) of English-language literature pertaining to the use of fomepizole in ethylene glycol poisoning was performed. Key search terms included fomepizole, ethylene glycol poisoning, and hemodialysis. References cited in those articles were also evaluated.

DATA SYNTHESIS

Results from a number of case reports and a prospective trial suggest that fomepizole is a safe and effective antidote in the treatment of ethylene glycol poisoning.

CONCLUSIONS

Case reports and 1 prospective trial have shown that, in the absence of both renal dysfunction and significant metabolic acidosis, the use of fomepizole should obviate the need for hemodialysis. However, the decision to add hemodialysis in the treatment of ethylene glycol poisoning based on plasma ethylene glycol concentrations is still debatable. A randomized, controlled trial is needed to determine the exact criteria for adding hemodialysis.