Acetylcysteine

Oral
As a mucolytic
Adult: As powder for oral solution: 200 mg tid. Max: 600 mg daily. As effervescent tab: 600 mg once daily.
Child: As powder for oral solution: 2-6 years 100 mg 2-4 times daily; >6 years 200 mg 2-3 times daily. As effervescent tab: >6 years 600 mg once daily.
Reconstitution: Effervescent granules or tab: Dissolve in a glass of water before use. Oral solution: Dilute the 20% solution with an orange juice, cola or any diet soft drinks to a final concentration of 5%.
Incompatibility: Incompatible with some metals (e.g. Fe, copper), rubber, oxygen and oxidising substances, some antimicrobials (e.g. amphotericin B, ampicillin Na, erythromycin lactobionate) and some tetracyclines.

Oral
Paracetamol poisoning
Adult: As effervescent tab: Initially, 140 mg/kg followed by 17 maintenance doses of 70 mg/kg given 4 hourly.
Child: Same as adult dose.
Reconstitution: Effervescent granules or tab: Dissolve in a glass of water before use. Oral solution: Dilute the 20% solution with an orange juice, cola or any diet soft drinks to a final concentration of 5%.
Incompatibility: Incompatible with some metals (e.g. Fe, copper), rubber, oxygen and oxidising substances, some antimicrobials (e.g. amphotericin B, ampicillin Na, erythromycin lactobionate) and some tetracyclines.

Inhalation
As a mucolytic
Adult: As 10% solution: 6-10 mL 3-4 times daily, may increase to 2-20 mL 2-6 hourly as necessary. As 20% solution: 3-5 mL 3-4 times daily, may increase to 1-10 mL 2-6 hourly as necessary.
Child: Same as adult dose.
Reconstitution: Inhalation: 20% solution may be diluted with NaCl 0.9% inj or inhalation solution, or sterile water for inj or inhalation.
Incompatibility: Incompatible with some metals (e.g. Fe, copper), rubber, oxygen and oxidising substances, some antimicrobials (e.g. amphotericin B, ampicillin Na, erythromycin lactobionate) and some tetracyclines.

Endotracheal
As a mucolytic
Adult: As 10% or 20% solution: 1-2 mL as often as every hour.
Child: Same as adult dose.
Reconstitution: For admin via gastric tube, use water as diluent. Oral solution: Dilute the 20% solution with an orange juice, cola or any diet soft drinks to a final concentration of 5%.
Incompatibility: Incompatible with some metals (e.g. Fe, copper), rubber, oxygen and oxidising substances, some antimicrobials (e.g. amphotericin B, ampicillin Na, erythromycin lactobionate) and some tetracyclines.

Intravenous
Paracetamol poisoning
Adult: Initially, 150 mg/kg (Max: 16.5 g) in 200 mL diluent over 1 hour, followed by 50 mg/kg (Max: 5.5 g) in 500 mL diluent over 4 hours, then 100 mg/kg (Max: 11 g) in 1 L diluent over the next 16 hours.
Child: <20 kg: Initially, 150 m g/kg in 3 mL/kg diluent over 1 hour, followed by 50 mg/kg in 7 mL/kg diluent over 4 hours, then 100 mg/kg in 14 mL/kg diluent over 16 hours; 20-39 kg: Initially, 150 mg/kg in 100 mL diluent over 1 hour, followed by 50 mg/kg in 250 mL diluent over 4 hours, then 100 mg/kg in 500 mL diluent over 16 hours; ≥40 kg: Same as adult dose.
Reconstitution: IV: Dilute for IV infusion with dextrose 5%, NaCl or sterile water for inj.
Incompatibility: Incompatible with some metals (e.g. Fe, copper), rubber, oxygen and oxidising substances, some antimicrobials (e.g. amphotericin B, ampicillin Na, erythromycin lactobionate) and some tetracyclines.

Ophthalmic
Dry eye associated with abnormal mucus production
Adult: As 5% solution: Instill 1 or 2 drops into the conjunctival sac of the affected eye(s) 3 or 4 times daily.
Incompatibility: Incompatible with some metals (e.g. Fe, copper), rubber, oxygen and oxidising substances, some antimicrobials (e.g. amphotericin B, ampicillin Na, erythromycin lactobionate) and some tetracyclines.

Use of oral powder for solution and effervescent tab in children below 2 years of age.

Patient with known or history of atopy and asthma, history of bronchospasm, history of. peptic ulcer disease, esophageal varices. Children. Pregnancy and lactation. Patient Counselling Ophthalmic: This drug may cause blurred vision, if affected, do not drive or operate machinery. Should not be used in patients who wear soft contact lenses. Monitoring Parameters Paracetamol poisoning: Monitor serum paracetamol levels, AST, ALT, bilirubin, prothrombin time, INR, serum creatinine, BUN, serum glucose, Hb, haematocrit and electrolytes.

Significant: Hypersensitivity reactions (e.g. urticaria, rash, hypotension, wheezing, dyspnoea); fluid overload resulting in hyponatraemia and seizures, decreased prothrombin time, acute flushing, skin erythema (IV); risk of upper gastrointestinal haemorrhage (oral); haemoptysis, rhinorrhoea, stomatitis (inhalation). Cardiac disorders: Cardiac arrest. Eye disorders: Ophthalmic: Itching, redness, eye irritation, blurred vision. Gastrointestinal disorders: Nausea, vomiting. General disorders and administration site conditions: Fever, sweating. Investigations: Liver function disturbances. Metabolism and nutrition disorders: Acidosis. Musculoskeletal and connective tissue disorders: Arthralgia. Nervous system disorders: Convulsion. Respiratory, thoracic and mediastinal disorders: Respiratory arrest. Vascular disorders: Hypo/hypertension, syncope.
Potentially Fatal: Serious hypersensitivity reactions (e.g. bronchospasm, angioedema), fluid overload resulting in hyponatraemia and seizures (IV).

Oral: Symptoms: Nausea, vomiting, diarrhoea, anaphylactoid reactions. Management: Symptomatic and supportive treatment. May administer antihistamines and steroids for anaphylaxis.

Build-up of bronchial secretions due to reduced cough reflex with antitussive drugs. Reduced effect with activated charcoal. May enhance the vasodilatory effects of nitroglycerin. May reduce the pharmacological effects of antibiotics.

May cause interference with colorimetric assay method for the determination of salicylates and with tests for ketones in urine.

Acetylcysteine exerts mucolytic action through its free sulfhydryl group which opens up the disulfide bonds in the mucoproteins, thus lowering mucous viscosity. It is a precursor of glutathione which serves as a substrate for the synthesis of glutathione in the body. In paracetamol toxicity, acetylcysteine acts as a hepatoprotective agent by restoring hepatic glutathione, serving as a glutathione substitute, and enhancing the nontoxic sulfate conjugation of paracetamol. Synonyms: N-acetylcysteine.
Onset: Inhalation: 5-10 minutes.
Duration: Inhalation: >1 hour.
Absorption: Rapidly absorbed from the gastrointestinal tract. Bioavailability: 4-10% (oral). Time to peak plasma concentration: 1-2 hours (oral solution), 1-3.5 hours (effervescent tablet).
Distribution: Crosses the placenta and detected in cord blood. Volume of distribution: 0.47 L/kg. Plasma protein binding: 66-87%.
Metabolism: Metabolised in the liver and metabolism in the gut wall to form cysteine and disulfides; cysteine is further metabolised to form glutathione and other metabolites. Undergoes extensive first-pass metabolism.
Excretion: Via urine (13-38%). Elimination half-life: 6.25 hours for total acetylcysteine (oral); 2-6 hours (IV).

Endotracheal: Effervescent tab/unopened soln: Store 20-25°C. Oral soln/Soln for inhalation: Following exposure to air, store between 2-8°C and use within 96 hours. Inhalation: Oral soln/Soln for inhalation: Following exposure to air, store between 2-8°C and use within 96 hours. Ophthalmic: Ophthalmic soln: Store below 25°C. Oral: Effervescent tab/unopened soln: Store 20-25°C. Oral soln/Soln for inhalation: Following exposure to air, store between 2-8°C and use within 96 hours.

Antidotes, Detoxifying Agents & Drugs Used in Substance Dependence / Cough & Cold Preparations / Ophthalmic Lubricants / 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.