Acetylcysteine

Glutathione Precursor·Toxicology & Antidotes

Paracetamol overdose

ANTIDOTEParvolex (IV)Ampoules (2 g/10 mL) for IV…S4TGA

Max Dose

Weight Based

Half-life

5.6 h

Anaphylactoid

HIGH RISK

Route

IV or PO

Rapid Summary

Overview

The definitive, life-saving antidote for Paracetamol (Acetaminophen) overdose. Replenishes hepatic glutathione to neutralize the toxic NAPQI metabolite.

Maximum Dose

Weight-based nomogram (Standard 2-bag or 3-bag protocol). Max weight used for calculations is usually 110 kg.

Clinical Focus

Must be started within 8 hours of ingestion for 100% efficacy against hepatotoxicity. Delays are fatal.

Bottom Line

Acetylcysteine is the life-saving antidote for paracetamol overdose when given within the treatment window, but the IV infusion commonly causes anaphylactoid reactions requiring rate adjustment.

Formulation & Access

Brand Names

Parvolex (IV)

Parenteral

Ampoules (2 g/10 mL) for IV infusion. Highly concentrated, must be diluted in D5W or Normal Saline.

Prescribing & PBS

Hospital supply.

Indications & Use

Primary

TGA

Paracetamol overdose.

Off-Label

OFF

Prevention of contrast-induced nephropathy, fulminant hepatic failure (non-paracetamol).

Clinical Place

Mandatory ED/ICU protocol drug. Plotted against the Rumack-Matthew nomogram.

Quick reference

Class & Role

Glutathione Precursor — The definitive, life-saving antidote for Paracetamol (Acetaminophen) overdose.

Route / Formulation

Ampoules (2 g/10 mL) for IV infusion. Highly concentrated, must be diluted in D5W or Normal Saline. (Parvolex (IV))

Usual Dose & Max

IV Bag 1: 200 mg/kg over 4 hours. Bag 2: 100 mg/kg over 16 hours. (Total 300 mg/kg over 20 hours). Weight-based nomogram (Standard 2-bag or 3-bag protocol). Max weight used for calculations is usually 110 kg.

Key Indication Doses

Paracetamol Overdose (2-Bag IV Protocol): IV Bag 1: 200 mg/kg over 4 hours. Bag 2: 100 mg/kg over 16 hours. (Total 300 mg/kg over 20 hours). Contrast Nephropathy Prophylaxis: PO 600 mg BD the day before and day of contrast (Off-label, evidence is highly debated). Mucolytic (CF/Bronchiectasis): Inhaled via nebuliser (Off-label).

Best Uses

Acetylcysteine is the life-saving antidote for paracetamol overdose when given within the treatment window, but the IV infusion commonly causes anaphylactoid reactions requiring rate adjustment.

Avoid / Cautions

NONE — In the context of a toxic paracetamol overdose, there are zero absolute contraindications to NAC.

Key Risks

Immunological: Non-IgE Anaphylactoid reactions (Flushing, rash, wheeze, hypotension). Most common during the first fast infusion bag. Gastrointestinal: Severe nausea and vomiting (can complicate PO administration).

Key Interactions

No major systemic interactions. However, it is chemically incompatible in the same IV line with many drugs (e.g., penicillins). Run on a dedicated line.

Monitoring

Baseline and end-of-infusion LFTs (ALT/AST), U&E, INR, and Paracetamol levels. Monitor closely during Bag 1 for anaphylactoid reactions. If flushing/wheeze occurs, stop infusion, give antihistamines, and restart at a slower rate once resolved.

Clinical Pearl

The classic 'NAC Rash' is an anaphylactoid (rate-related histamine release), not a true IgE anaphylaxis. You do not need to abandon the drug. Slow the rate, treat the histamine, and push through. The liver needs the antidote.

Access

Parvolex (IV)

Brand: Parvolex (IV)

Acetylcysteine

Glutathione Precursor·Toxicology & Antidotes

Paracetamol overdose

ANTIDOTEParvolex (IV)Ampoules (2 g/10 mL) for IV…S4TGA

Max Dose

Weight Based

Half-life

5.6 h

Anaphylactoid

HIGH RISK

Route

IV or PO

Rapid Summary

Overview

The definitive, life-saving antidote for Paracetamol (Acetaminophen) overdose. Replenishes hepatic glutathione to neutralize the toxic NAPQI metabolite.

Maximum Dose

Weight-based nomogram (Standard 2-bag or 3-bag protocol). Max weight used for calculations is usually 110 kg.

Clinical Focus

Must be started within 8 hours of ingestion for 100% efficacy against hepatotoxicity. Delays are fatal.

Bottom Line

Acetylcysteine is the life-saving antidote for paracetamol overdose when given within the treatment window, but the IV infusion commonly causes anaphylactoid reactions requiring rate adjustment.

Formulation & Access

Brand Names

Parvolex (IV)

Parenteral

Ampoules (2 g/10 mL) for IV infusion. Highly concentrated, must be diluted in D5W or Normal Saline.

Prescribing & PBS

Hospital supply.

Indications & Use

Primary

TGA

Paracetamol overdose.

Off-Label

OFF

Prevention of contrast-induced nephropathy, fulminant hepatic failure (non-paracetamol).

Clinical Place

Mandatory ED/ICU protocol drug. Plotted against the Rumack-Matthew nomogram.

Quick reference

Class & Role

Glutathione Precursor — The definitive, life-saving antidote for Paracetamol (Acetaminophen) overdose.

Route / Formulation

Ampoules (2 g/10 mL) for IV infusion. Highly concentrated, must be diluted in D5W or Normal Saline. (Parvolex (IV))

Usual Dose & Max

Key Indication Doses

Best Uses

Acetylcysteine is the life-saving antidote for paracetamol overdose when given within the treatment window, but the IV infusion commonly causes anaphylactoid reactions requiring rate adjustment.

Avoid / Cautions

NONE — In the context of a toxic paracetamol overdose, there are zero absolute contraindications to NAC.

Key Risks

Key Interactions

No major systemic interactions. However, it is chemically incompatible in the same IV line with many drugs (e.g., penicillins). Run on a dedicated line.

Monitoring

Clinical Pearl

Access

Parvolex (IV)

Brand: Parvolex (IV)