The Pharmaceutical Journal
Vol 278 No 7435 p85-88
20 January 2007

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Over-the-counter advice for coughs

About 48 million cases of acute cough occur annually in the UK and most will prompt patients to use over-the-counter medicines. In this article, Sarah Marshall gives an overview of coughs and factors that pharmacists should consider

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SUMMARY

A cough is a protective reflex invoked when something blocks or irritates the airway. It is a forced expulsive manoeuvre, usually against a closed glottis (the opening between the vocal cords), associated with a characteristic sound. Its purpose is to maintain normal breathing by removing mucus or noxious substances from the larynx, trachea and larger bronchi.

The reflex is complex but can be pictured in three phases:

•Receptors in the respiratory tract mucosa respond to chemical or mechanical stimuli and discharge impulses along cholinergic nerve fibres

•These impulses are received by the cough centre(s) in the brain

•The cough centre sends impulses along cholinergic nerve pathways, causing the diaphragm and abdominal and intercostal muscles to contract, resulting in the cough

Coughing is a non-specific symptom that can be linked to over 100 conditions, ranging from minor and self-limiting to life-threatening. The sensitivity of the cough reflex can increase with infection, some diseases and the use of some drugs.

An acute cough (defined as one lasting less than three weeks) is the most common reason for patients to consult their GP — accounting for 12 million visits a year — and is often associated with an upper respiratory tract infection (URTI).

There are at least 200 viruses that can lead to such infections, resulting in hypersecretion of mucus by goblet cells and vasodilation and, therefore, nasal congestion, sneezing, nasal discharge, post-nasal drip (mucus drips from the post-nasal space and irritates the pharynx and trachea), which in turn lead to throat clearing and cough.

If a cough lasts more than eight weeks, it is described as chronic. Chronic coughs are typically dry or minimally productive. Examples of common causes of chronic cough include adverse drug reactions, exposure to environmental aggravants and gastro-oesophageal reflux or upper airway disease.

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