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Carbocysteine is a pharmacologically classified mucolytic. In other countries, it may be spelled as carbocisteine.


Chemical nature

Carbocysteine has a molecular formula of C5H9NO4S with a systemic name of (R)-2-Amino-3-(carboxymethylsulfanyl)propanoic acid. It is also known as S-Carboxymethyl-L-cysteine. This is drug is chemically related to acetylcysteine, which is another mucolytic. It is manufactured by alkylating cysteine, an amino acid, with chloroacetic acid.

Carbocysteine works by reducing the thickness of mucosal secretions that obstruct the airways. The less sticky the phlegm due to increased sialomucin content, the easier it is to cough up. This is very effective in relieving the symptoms of chronic obstructive pulmonary disorder. In addition, the sialomucin reduces spasms and inflammation of the airways.

Carbocysteine is rapidly absorbed by the gastro-intestinal tract and will penetrate lung tissues. It is considered superior to bromhexine as it does not produce ciliary lesions in the trachea and bronchi and has no effect on the nervous system (i.e. drowsiness, depression).

Uses and common dosages

Carbocysteine is an over-the-counter medication that may be given to assist treatment of chronic bronchitis, chronic obstructive pulmonary disease, and otitis media with effusions. It must be taken with food as it might cause stomach upset. At 1 hour and 30 minutes, full effect of the dose will be felt.

Adults are given an initial dose of 750 milligrams thrice a day of carbocysteine and will be lowered to 500 milligrams thrice a day. Children younger than 2 years old are not advised to take carbocysteine unless under medical supervision. Those aged 2 to 5 years old may be given 62.5 to 125 milligrams every 6 hours. If aged 7 to 12, a dose of 250 milligrams every 8 hours will suffice.

Side effects

A common side effect with carbocysteine therapy is stomach upset, dry mouth, and nausea. However, it might also produce flatulence, gastrointestinal ulceration and bleeding. Skin rash may also develop but it rarely happens.

When insomnia, headache, palpitations and mild hypoglycemia develop, healthcare providers might adjust dosage for the rest of the treatment period with carbocysteine or shift to other mucolytics that will not produce such adverse effects.

If severe allergic reactions (swelling of face or throat, hives, difficulty breathing and tightness of the chest), fine tremors, blood in the stools, irregular heartbeats and vomit that looks like coffee grounds, treatment with carbocysteine must stop.

Precautions and contraindications

Carbocysteine causes active ulceration of the gastrointestinal tract so people with history of ulcers must reconsider

Carbocysteine must never be used with antitussives such as dextromethorphan or codeine, as the latter dries up bronchial secretions. It will increase the perfusion of antibiotics such as cephalosporins in the lung tissue.


Carbocysteine is available in the Philippines in a variety of dosage forms. There are capsules, suspensions, syrups, drops, and chewable tablets. It requires no prescription and is available in 250 and 500 milligram capsules. Liquid formulations are available at 100 or 250 milligrams per 5 milliliters in bottles of 60 or 120 milliliters. The chewable tablet is available only at 500 milligrams. A popular brand that provides a variety of dosage forms to choose from is Solmux ®. This drug may also be combined with salbutamol.