A cough is a sudden expiratory thrust of air from the lungs. It is essentially a protective reflex. Coughing is useful when it effectively removes secretion or extraneous material from the respiratory tract, that is, when it is productive. It is useless when it is unproductive. It has been said that more people have died from an inability to cough rather than from the act of coughing. Does this mean that coughing is always useful and should never be prevented? No. The unproductive or useless cough is often very troublesome and needs to be stopped.

Causes: The causes of coughs need not be restricted to the respiratory system, though a vast majority of them are concerned with irritation and diseases of the respiratory tract. A cough may be a manifestation of a disease of the heart or lungs. How then do we discover the actual cause? Consideration of such factors as duration of the cough, its tendency to occur at particular times, the nature of the sputum brought up, and other complaints of the patient, all help in establishing Its source. A short cough is usual in upper airways infections such as the common cold, infection of throat and sound box while prolonged coughing is characteristic of chronic bronchitis and bronchiectasis. In children whooping cough occurs in bouts and is followed by deep inhalation (whoop). A similar situation is croup but here there is inspiratory difficulty. Cough may be a manifestation of respiratory allergy, bronchial asthma, obstruction of airway passages by foreign bodies (supari, pan masala) or could be due to a more sinister cause such as cancer of lungs. Coughing and expectoration of sputum are often most troublesome in the early morning and at bedtime, especially in chronic bronchitis. Sometimes a cough may be influenced by psychological considerations.

Treatment

Removal of the underlying cause is essential when the cough is indicative of a more serious disease. It could, for example, be indicative of an infective condition of the chest. In this chapter we will restrict ourselves to drugs meant to provide symptomatic relief for a cough.

As everyone knows, a mild tickling at the back of one's throat induces a bout of cough. This is exactly what happens when the pharynx and larynx (parts of the throat) get irritated by infection or irritants, such as dust, fumes, or smoke. Therefore, our aim should be to reduce the irritation and this can be achieved by adopting such simple measures as giving up smoking, sucking cough lozenges or candy sugar, inhaling water vapours - either plain or medicated, and staying in a warm humid environment till the irritation is relieved.

For coughs originating from parts still lower down in the respiratory tract, numerous medications are available. Broadly these are of two types.

Codeine (Codine Linctus/Tab, Corex, Exiplon)

It has been in use for dry cough but constipation is the main adverse effect. It should not be used in bronchial asthma (dose 10mg twice a day).

Dextromethorphan (Alex, Deletus-d, Clistim-dmr, Lastuss-la)

It is a common ingredient in lozenges and syrups. Antihistaminics and decongestants are also combined. It does not cause constipation but should not be used in newborns and during pregnancy. Dizziness, drowsiness and difficulty of walking are adverse effects (usual dose 10 to 20mg two to three times a day). Pholcodeine, oxeladin, chlorphedianol are found in some preparations.