HEALTH / Common Remedies: Cough mixture

DOCTORS rarely prescribe cough mixtures; pharmacists sell vast quantities of them every winter. Why is there such a wide gulf between the consumer demand and the professional response?

The medical argument is logical enough. The cough reflex is one of the most important protective devices for the body. Someone who cannot cough because of brain damage after a head injury, or has taken an overdose of drugs, has a high risk of developing pneumonia. Around 100ml of fluid is formed in the lungs every day, which, with sticky mucus in the air passages, has to be propelled out - partly by the movement of small hairs (cilia) that line the passage ways, and partly by coughing.

Someone with a lung infection such as pneumonia or bronchitis, or with heart failure, will form more fluid and mucus and so needs to cough more. In these circumstances giving treatment to stop the patient coughing is likely to worsen the illness.

So faced with a patient complaining about a cough, the doctor's response should be to decide the cause and whether it is doing a useful job. If it is, then any cough medicine prescribed will be to make the mucus thinner and easier to cough up.

Expectorant cough mixtures are based on mucus-thinning drugs, many of them plant extracts. The official prescribing manual, the British National Formulary, says 'there is no scientific basis for prescribing any of these preparations', but they have been popular for hundreds of years and at least often make patients feel better.

Sometimes, however, a cough is distressing but seems to have no useful effect. Quite often a virus infection of the nose and throat will cause a cough - there is a detectable tickle of irritation at the back of the throat. Such coughs may often be eased a little by a linctus or throat lozenges. But they rarely last for more than a few days.

A cough may also be a troublesome and upsetting feature of lung cancer too advanced for cure, when treatment will be given to block the nerve centres in the brain that control coughing. The most powerful cough suppressants are morphine and heroin, used for patients with terminal cancer.

Many other factors influence coughing, and it is often better to attend to these rather than to expect a cough medicine to work wonders. Cold dry air makes coughs worse; moist warm air makes coughs better. The English tradition of sleeping with the windows open has a devastating effect; anyone with a winter cold and victims of chronic bronchitis should sleep in a warm bedroom with some sort of humidifier, such as a damp towel over the radiator.

The smoker's cough is due partly to irritation and inflammation of the air passages by smoke and partly to the damage smoke causes to the cilia. The best cough medicine is to stop smoking.