Carbocisteine

Carbocisteine is an oral mucolytic used to reduce sputum viscosity in chronic bronchitis and COPD, and in children with productive cough on clinical advice. Evidence shows a modest reduction in exacerbations in COPD.

Classification. Mucolytic, mucoregulator.

Mechanism. Alters the balance of sialomucins and fucomucins, reducing mucus viscosity, and has some antioxidant and anti-inflammatory effects.

Pharmacokinetics. Rapidly absorbed. Half-life about 2 hours. Metabolised by acetylation, decarboxylation and sulphoxidation, with marked variation between individuals. Excreted in urine.

Alternative, chronic bronchitis and COPD with thick sputum, adults. 750 mg three times daily initially, reduced to 1500 mg daily in divided doses once there is a good response.

Children 6 to 12 years. 250 mg three times daily. Children 2 to 5 years. 62.5 to 125 mg four times daily. Under 2 years: not advised.

Emergency and specialist use. None.

Titration and loading. No loading dose. Reduce once the response is established.

Contraindications. Active peptic ulcer, hypersensitivity, children under 2 years.

Serious adverse effects. Gastrointestinal bleeding, rare severe skin reactions (erythema multiforme, bullous eruptions), anaphylaxis.

Common adverse effects. Nausea, diarrhoea, abdominal discomfort, rash.

Interactions. Cough suppressants cause secretion accumulation. Gastric irritant drugs (NSAIDs, corticosteroids) add to ulcer risk.

Common prescribing errors. Prescribing with a cough suppressant. Prescribing to a patient with active peptic ulcer or previous gastrointestinal bleeding.

Special groups.

• Pregnancy: avoid in the first trimester; limited data after. Breastfeeding: no data; avoid.

• Older adults: take care with gastrointestinal bleeding risk and give with food.

• Kidney impairment: no adjustment. Liver impairment: no specific adjustment.

• East Africa: syrups may contain sugar, which matters in diabetes. Test for tuberculosis when cough lasts over 2 weeks.

Formulations. Capsules 375 mg, syrup 125 mg/5 mL and 250 mg/5 mL, sachets 750 mg.

Administration. Give with food to reduce gastric irritation.

Baseline. History of peptic ulcer or gastrointestinal bleeding, NSAID and corticosteroid use.

Monitoring. Sputum, exacerbations and gastrointestinal symptoms.

Stop and reduce rules. Stop for gastrointestinal bleeding, severe skin reaction or no benefit after 4 weeks. Therapeutic drug monitoring is not used.

Referral and escalation. Refer for black stools, haematemesis, haemoptysis or cough over 2 weeks.