Pholcodine

Pholcodine is a drug which is an opioid cough suppressant (antitussive). It helps suppress unproductive coughs and also acts as an antifungal agent. It also has a mild sedative effect, but has little or no analgesic effects.

Pholcodine is found in certain cough lozenges. However, in the UK, the preparation is almost exlusively an oral solution, typically 5 mg / 5 ml. Adult dosage is 5-10ml up to 3-4 times daily. Pholcodeine now largely replaces the previously more common codeine linctus, as it has a much lower potential for dependence.

Mechanism of action

Pholcodine is readily absorbed from the gastrointestinal tract and freely crosses the blood-brain barrier. It acts primarily on the central nervous system (CNS), causing depression of the cough reflex, partly by a direct effect on the cough centre in the medulla. It is metabolized in the liver and its action may be prolonged in individuals with hepatic insufficiency (i.e. liver problems). Its use is therefore contraindicated in patients with liver disease, while care is advised in patients with hepatic impairement.

Side effects

Side effects are rare and may include dizziness and gastrointestinal disturbances such as nausea or vomiting.

Adverse effects such as constipation, drowsiness, excitation, ataxia and respiratory depression have been reported occasionally or after large doses.

A Norwegian cough-syrup containing pholcodine ("Tuxi") has been withdrawn from the market because it caused increased levels of IgE-antibodies, regardless of an actual allergy to the drug. This is believed to increase the risk of anaphylaxis to neuromuscular blocking agents used during anaesthesia.