N-Acetyl-L-Cysteine (Acetylcysteine)

N-Acetyl-L-Cysteine (Acetylcysteine)

Available presentation(s): 30 mL. Verify the exact concentration and total active quantity on the prescription and dispensing label.

Introduction: N-acetyl-L-cysteine (acetylcysteine) replenishes glutathione and is an established antidote for paracetamol overdose. Intravenous use should follow a recognised toxicology protocol.

Dosage: For paracetamol poisoning, use the current National Poisons Centre/local hospital weight-based regimen and seek toxicology advice; regimens vary and errors can cause serious harm. Orders must specify patient weight, total dose, diluent volumes, infusion durations and criteria for continuation. The 200 mg/mL concentrate requires dilution.

Mechanisms of Action: Restores hepatic glutathione, directly reduces the reactive paracetamol metabolite NAPQI and may improve microcirculatory blood flow and antioxidant capacity.

Contraindications & Precautions: Use caution in asthma, previous anaphylactoid reaction and fluid-restricted patients. Monitor during loading doses; pause and treat significant reactions according to protocol. Adjust diluent volumes for children or fluid restriction.

Interactions: Activated charcoal may reduce oral but not IV exposure. Nitroglycerin-associated hypotension/headache can be enhanced. Do not mix with incompatible antibiotics or metals; use validated compatibility data.

Adverse Reactions / Side Effects: Nausea, vomiting, flushing, urticaria and pruritus are common. Anaphylactoid reactions with bronchospasm, angioedema or hypotension can occur, especially early in treatment; dosing errors can cause hyponatraemia, seizures or fluid overload.

Pregnancy & Breastfeeding: Treatment of maternal paracetamol poisoning should not be delayed; acetylcysteine is used when indicated in pregnancy. Breastfeeding is generally manageable during clinically necessary treatment, subject to toxicology advice.

Storage: Store under the conditions stated on the Optimus dispensing label and product-specific worksheet. Protect from light where labelled. Do not freeze unless explicitly validated. Maintain cold chain if the label requires refrigeration. Do not use after the assigned beyond-use date or if there is visible particulate matter, precipitation, colour change, loss of container integrity or evidence of improper storage. Once entered, follow the validated in-use time; do not assume a compounded vial is multi-dose.

References

• New Zealand Formulary (NZF), current online edition; product-specific approved data sheets where available; USP Pharmaceutical Compounding—Sterile Preparations; and Optimus Healthcare validated formulation, sterility/endotoxin controls and assigned beyond-use date.
• DailyMed. Acetylcysteine Injection—prescribing information, current edition. https://dailymed.nlm.nih.gov/
• US FDA. Compounding and the FDA: Questions and Answers. Updated 16 September 2025. https://www.fda.gov/drugs/human-drug-compounding/compounding-and-fda-questions-and-answers