Oral methionine compared with intravenous n-acetyl cysteine for paracetamol overdose
Date First Published:
January 20, 2002
Last Updated:
July 1, 2003
Report by:
Walid Alsalim, SPR in Emergency Medicine (Norfolk & Norwich University Hospital)
Search checked by:
Mohamed Fadel, Norfolk & Norwich University Hospital
Three-Part Question:
In a [patient with paracetamol overdose within eight hours] is [methionine as good as or better than n-acetyl cysteine] at [reducing liver damage]?
Clinical Scenario:
A 19 year old woman is brought to the emergency department 6 hours after paracetamol overdose. She is fully conscious and admits ingestion of 32 tablets of paracetamol. She is complaining of abdominal discomfort but no nausea or vomiting. Her examination is unremarkable. You arranged blood investigations. IV access and n-acetyl cysteine infusion started as per protocol. You wonder whether oral methionine would have been as effective as n-acetyl cysteine in her treatment.
Search Strategy:
Medline 1966-04/03 using the OVID interface.
Search Details:
[exp methionine OR methionine$.mp] AND [exp acetaminophen OR acetaminophen$.mp OR paracetamol.mp] AND [exp acetylcysteine OR acetylcysteine$.mp OR parvolex.mp] LIMIT to human AND English.
Outcome:
Altogether 39 papers were found, of which 2 were relevant.
Relevant Paper(s):
| Study Title | Patient Group | Study type (level of evidence) | Outcomes | Key results | Study Weaknesses |
|---|---|---|---|---|---|
| Treament of Acetaminophen poisoning. Vale JA and Meredith TJ. 1981, UK | 158 patients with paracetamol overdose. Mean age: 26 ys 1:2 M, F ratio High risk patients defined as paracetamol level: >300mg/l at 4 h. |
Prospective observational | Liver damage: | NSD | No randomisation Small study 2 out of the 7 vomited the first dose |
| Methionine within 10h (n=96) | 7% | ||||
| IV n-acetylcysteine within 10h (n=62) | 2% | ||||
| In high risk patients methionine within 10 h (n=43) | 14% | ||||
| In high risk patients IV n-acetylcysteine within 10 h (n=33) | 3% | ||||
| Treatment of severe Acetaminophen poisoning with intravenous Acetylcysteine. Prescott LF. 1981, UK | 104 patients with paracetamol overdose. Mean group 33ys. 1:1.5 M,F Ratio High risk patients defined as paracetamol level: >300mg/l at 4h |
Prospective observational | Liver damage: | NSD | No randomisation Small study |
| Methionine. Within 10 h (n=42) 57% of them were high risk | 7% | ||||
| IV n-acetyl cysteine within 10 h (n=62) 33/62 (53%) of them were high risk | 2% |
Author Commentary:
There have been no randomised controlled trials and only two prospective observational studies comparing these two drugs. However, patients in these two studies had the antidote within eight hours.
Bottom Line:
IV acetylcysteine (parvolex) is more effective than methionine at preventing liver damage in patients after paracetamol overdose.
References:
- Vale JA and Meredith TJ.. Treament of Acetaminophen poisoning.
- Prescott LF.. Treatment of severe Acetaminophen poisoning with intravenous Acetylcysteine.