Acetylcysteine

Oral
As a mucolytic
Adult: As adjunctive therapy for respiratory tract disorders associated with excessive, viscous mucus: As granules for oral solution: 200 mg 2-3 times daily. As effervescent tab: 600 mg once daily. Treatment duration may vary depending on the nature and severity of the disease. Dosage recommendations may vary among countries and individual products (refer to specific product guidelines).
Child: 2-6 years As granules for oral solution: 100 mg 2-4 times daily; >6 years Same as adult dose. Treatment or dosage recommendations may vary among countries and individual products (refer to specific product guidelines).
Reconstitution: Effervescent tab: Dissolve tab in a glass of water before administration. Granules for oral solution: Dissolve the contents of the sachet into a glass of water and stir with a spoon if necessary.
Incompatibility: Incompatible with certain metals (e.g. Fe, Cu), rubber, amphotericin B, ampicillin Na, erythromycin lactobionate, some tetracyclines, iodised oil, chymotrypsin, trypsin, and hydrogen peroxide.

Oral
Paracetamol poisoning
Adult: Initiate treatment as soon as possible following the overdose or within 24 hours of ingestion. As 5% oral solution (diluted 20% solution) or effervescent tab (diluted in appropriate volume of water): Loading dose: 140 mg/kg. Maintenance: 70 mg/kg 4 hourly for 17 doses. If emesis occurs within 1 hour of administration, repeat the dose. Refer to specific product guidelines for further dosing information.
Child: Same as adult dose.
Reconstitution: Effervescent tab: Dissolve tab in a glass of water before administration. As 5% oral solution: Dilute the 20% solution with diet cola or other diet soft drinks to achieve a final concentration of 5%. Refer to detailed product guidelines for specific instructions on preparation.
Incompatibility: Incompatible with certain metals (e.g. Fe, Cu), rubber, amphotericin B, ampicillin Na, erythromycin lactobionate, some tetracyclines, iodised oil, chymotrypsin, trypsin, and hydrogen peroxide.

Inhalation
As a mucolytic
Adult: As adjunctive therapy for respiratory tract disorders associated with excessive, viscous mucus: As 10% solution: 6-10 mL 3-4 times daily; if necessary, may give 2-20 mL 2-6 hourly. As 20% solution: 3-5 mL 3-4 times daily; if necessary, may give 1-10 mL 2-6 hourly. In preparation for diagnostic bronchial studies (bronchograms, bronchospirometry, bronchial wedge catheterisation): 2-4 mL of 10% solution or 1-2 mL of 20% solution to be given 2-3 times before the procedure. Doses are given via nebulisation (e.g. through a face mask or mouthpiece). Refer to specific product guidelines for further instructions on administration.
Reconstitution: As 20% solution: May dilute to a lesser concentration with 0.9% NaCl or sterile water for inj or inhalation.
Incompatibility: Incompatible with certain metals (e.g. Fe, Cu), rubber, amphotericin B, ampicillin Na, erythromycin lactobionate, some tetracyclines, iodised oil, chymotrypsin, trypsin, and hydrogen peroxide.

Endotracheal
As a mucolytic
Adult: As adjunctive therapy for respiratory tract disorders associated with excessive, viscous mucus: As 10% or 20% solution: 1-2 mL as often as every hour via direct instillation. Use in the routine nursing care of patients with tracheostomy: As 10 or 20% solution: 1-2 mL 1-4 hourly via instillation into the tracheostomy. Alternatively, 2-4 mL of 10% solution or 1-2 mL of 20% solution may be given 1-4 hourly through percutaneous intratracheal catheter. In preparation for diagnostic bronchial studies (bronchograms, bronchospirometry, bronchial wedge catheterisation): 2-4 mL of 10% solution or 1-2 mL of 20% solution to be given 2-3 times before the procedure.
Reconstitution: As 20% solution: May dilute to a lesser concentration with 0.9% NaCl or sterile water for inj or inhalation.
Incompatibility: Incompatible with certain metals (e.g. Fe, Cu), rubber, amphotericin B, ampicillin Na, erythromycin lactobionate, some tetracyclines, iodised oil, chymotrypsin, trypsin, and hydrogen peroxide.

Intravenous
Paracetamol poisoning
Adult: 21-hour regimen: Initially, 150 mg/kg in 200 mL of diluent via infusion over 1 hour, followed by 50 mg/kg in 500 mL of diluent infused over the next 4 hours and then 100 mg/kg in 1,000 mL of diluent infused over the next 16 hours. Treatment may be continued using the same dose and rate as the 3rd infusion depending on the individual clinical evaluation. Refer to specific product guidelines for further dosing information.
Child: 21-hour regimen: 5-20 kg: Initially, 150 mg/kg in 3 mL/kg of diluent via infusion over 1 hour, followed by 50 mg/kg in 7 mL/kg of diluent infused over 4 hours and then 100 mg/kg in 14 mL/kg of diluent infused over 16 hours; 21-40 kg: Initially, 150 mg/kg in 100 mL of diluent infused over 1 hour, followed by 50 mg/kg in 250 mL of diluent infused over 4 hours and then 100 mg/kg in 500 mL of diluent infused over 16 hours; ≥41 kg: Same as adult dose. Volume of the diluent must be adjusted to consider the age and weight of the patient. Recommendations may vary among countries and individual products (refer to specific product guidelines).
Reconstitution: IV: Dilute with 5% dextrose in water, 0.9% NaCl, sterile water for inj, or 0.45% NaCl solutions.
Incompatibility: Incompatible with certain metals (e.g. Fe, Cu), rubber, amphotericin B, ampicillin Na, erythromycin lactobionate, some tetracyclines, iodised oil, chymotrypsin, trypsin, and hydrogen peroxide.

Ophthalmic
Dry eye
Adult: For the relief of cases associated with tear deficiency, impaired or abnormal mucus production: As 5% eye drops solution: Instil 1 or 2 drops into the conjunctival sac(s) of the affected eye(s) 3 or 4 times daily.

Effervescent tab: Should be taken with food. Dissolve in 1/2 glass of water before taking.

For mucolytic use (oral): Children <2 years.

Patient with asthma, history of bronchospasm, atopy; decreased cough reflex (e.g. frail patient), predisposition to gastrointestinal haemorrhage [e.g. oesophageal varices, peptic ulcer] (oral). Patient requiring fluid restriction or who weighs ≤40 kg (IV). Acetylcysteine is available in multiple dosage forms, refer to detailed product guidelines for specific recommendations. Children. Pregnancy and lactation. Patient Counselling Ophthalmic: This drug may cause blurred vision after use, if affected, do not drive or operate machinery. Remove contact lenses before administration and allow a 15-minute interval before reinserting lenses. Monitoring Parameters Monitor pulmonary function and response to treatment. For paracetamol poisoning: Monitor serum paracetamol concentrations, AST, ALT, bilirubin, prothrombin time, INR, serum creatinine, BUN, serum glucose, Hb, haematocrit, and electrolytes; re-assess LFTs 4-6 hourly for possible hepatotoxicity. Observe for anaphylactoid reactions (particularly with IV use).

Significant: Increased risk of upper gastrointestinal haemorrhage (oral), small increase in prothrombin time (IV). Rarely, bronchospasm; serious skin reactions (e.g. Stevens-Johnson syndrome, Lyell's syndrome), generalised urticaria (oral). Blood and lymphatic system disorders: Thrombocytopenia (IV). Cardiac disorders: Tachycardia; cardiac arrest (IV). Ear and labyrinth disorders: Tinnitus (oral). Eye disorders: Eye irritation, pain or swelling, blurred vision. Gastrointestinal disorders: Nausea, vomiting, stomatitis; diarrhoea, abdominal pain (oral). General disorders and administration site conditions: Pyrexia, chest tightness; malaise, facial pain (IV). Metabolism and nutrition disorders: Acidosis (IV). Musculoskeletal and connective tissue disorders: Arthralgia, arthropathy (IV). Nervous system disorders: Headache (oral); drowsiness (inhalation/endotracheal). Psychiatric disorders: Anxiety (IV). Respiratory, thoracic and mediastinal disorders: Rhinorrhoea; throat tightness, pharyngitis, rhonchi, cough, stridor (IV); tracheal and bronchial tracts irritation (inhalation/endotracheal). Skin and subcutaneous tissue disorders: Pruritus, rash, angioedema; exanthema (oral); hyperhidrosis (IV). Vascular disorders: Hypotension; flushing, vasodilation, syncope, cyanosis (IV).
Potentially Fatal: Fluid overload resulting in hyponatraemia and seizures (IV). Rarely, anaphylactoid reactions (particularly with IV use).

Symptoms: Nausea, vomiting, diarrhoea; anaphylactoid reaction and bronchospasm (IV). Management: Symptomatic and supportive treatment.

Concomitant use with antitussives may lead to a build-up of secretions due to suppressed cough reflex; avoid concurrent use. May increase the vasodilatory and platelet aggregation-inhibiting effect of glyceryl trinitrate.

May affect the colourimetric assay of salicylates. May cause false-positive ketone bodies result in urinalysis.

Acetylcysteine is an N-acetyl derivative of the amino acid L-cysteine. It exhibits its mucolytic action through its free sulfhydryl group that breaks up the disulfide linkages of mucoproteins, thus reducing mucous viscosity; this action may also benefit patients with ocular mucus abnormality. In paracetamol poisoning, acetylcysteine acts as a hepatoprotective agent by maintaining or restoring the hepatic glutathione levels, or by acting as an alternate substrate for conjugation with, and therefore detoxification of, the toxic intermediate metabolite (N-acetyl-p-benzoquinoneimine) of paracetamol. Synonym: N-acetylcysteine.
Onset: Inhalation: 5-10 minutes.
Duration: Inhalation: >1 hour.
Absorption: Rapidly and almost completely absorbed from the gastrointestinal tract. Bioavailability: 4-10% (oral). Time to peak plasma concentrations: Approx 1-3 hours (oral).
Distribution: Crosses the placenta. Plasma protein binding: 66-87%.
Metabolism: Undergoes extensive first-pass metabolism to form cysteine (active metabolite), N,N-diacetylcysteine and N-acetylcysteine; cysteine undergoes further metabolism to form glutathione and other metabolites.
Excretion: Via urine (13-38%; almost entirely as inactive metabolites). Elimination half-life: Oral: 6.25 hours (total acetylcysteine). IV: 5.6 hours (total acetylcysteine); 2 hours (reduced acetylcysteine).

Endotracheal: Store unopened vials between 20-25°C. Once opened, store undiluted vials between 2-8°C and use within 96 hours. Protect from light. Storage recommendations may vary among countries and individual products. Refer to specific product guidelines. Inhalation: Solution for inhalation: Store unopened vials between 20-25°C. Once opened, store undiluted vials between 2-8°C and use within 96 hours. Storage recommendations may vary among countries and individual products. Refer to specific product guidelines. Intravenous: IV solution: Store intact vials between 20-25°C. Store reconstituted solution at room temperature for 24 hours. Storage recommendations may vary among countries and individual products. Refer to specific product guidelines. Ophthalmic: Ophthalmic solution: Store below 25°C. Protect from light. Storage recommendations may vary among countries and individual products. Refer to specific product guidelines. Oral: Effervescent tab: Store between 20-25°C. Protect from moisture. Granules for oral solution: Store below 30°C. Storage recommendations may vary among countries and individual products. Refer to specific product guidelines.

Antidotes, Detoxifying Agents & Drugs Used in Substance Dependence / Cough & Cold Preparations / Other Eye Preparations

V03AB23 - acetylcysteine ; Belongs to the class of antidotes. Used to neutralize paracetamol overdose.
S01XA08 - acetylcysteine ; Belongs to the class of other ophthalmologicals.
R05CB01 - acetylcysteine ; Belongs to the class of mucolytics. Used in the treatment of wet cough.