acetylcysteine: clinical use

Prescribing considerations

• Confirm the indication and product because oral, intravenous and ocular formulations are not interchangeable.
• Before oral treatment, assess asthma or bronchospasm history, ability to expectorate, peptic-ulcer history, histamine intolerance, hepatic or renal impairment and relevant excipient restrictions.
• Intravenous administration requires safeguards against preparation errors, fluid overload and infusion reactions.
• Review sodium and sugar-related excipients where dietary restriction, metabolic disease or intolerance is relevant.

Contraindications and cautions

• There are no contraindications to intravenous acetylcysteine when treating paracetamol overdose; previous hypersensitivity-like reactions do not automatically preclude treatment.
• Oral products are contraindicated in hypersensitivity to acetylcysteine or relevant excipients. The selected powder is contraindicated in phenylketonuria because it contains aspartame.
• Mucolytics must not be used in children under 2 years. The selected high-strength effervescent tablet is for adults and is unsuitable for children and adolescents.
• Ilube is contraindicated in hypersensitivity to acetylcysteine or its excipients.

Monitoring

• Observe for flushing, rash, vomiting, angioedema, bronchospasm and haemodynamic instability during intravenous treatment.
• In paracetamol poisoning, monitor clinical status and relevant liver, coagulation, renal, electrolyte and potassium results.
• Monitor fluid balance and sodium, particularly in children, lower-weight patients or people requiring fluid restriction.
• Stop oral treatment if bronchospasm or serious skin or mucosal lesions develop. Ensure secretions can be cleared effectively.
• During prolonged Ilube use, monitor patients with dry eye or a compromised corneal surface.
• Flag acetylcysteine exposure to the laboratory where susceptible assays are used.

Clinical pharmacology

Acetylcysteine is a thiol-containing cysteine derivative. It cleaves mucus disulphide bonds and supplies cysteine for glutathione synthesis, supporting detoxification of reactive paracetamol metabolites. Oral bioavailability is low because of extensive first-pass metabolism.

Formulation and product differences

• Acetylcysteine 200 mg/mL injection and Parvolex concentrate are hospital intravenous products for paracetamol overdose.
• Acepiro 600 mg effervescent tablets are an adult oral mucolytic containing sodium, lactose and sorbitol; they must be completely dissolved.
• Acetylcysteine 200 mg powder for oral solution is a mucolytic containing aspartame, sorbitol and sunset yellow; the selected product is unsuitable for phenylketonuria.
• Ilube contains acetylcysteine 5% with hypromellose and benzalkonium chloride for ocular mucus and dry eye; it is not interchangeable with respiratory products.

Solution for infusion

Route: Intravenous

Strengths: 200 mg/mL

Effervescent tablet

Route: Oral

Strengths: 600 mg

Oral solution

Route: Oral

Strengths: 200 mg

Injection

Route: Parenteral

Strengths: 200 mg/mL