COUGH
Cough is a protective reflex by which an irritant or obstructive material is expelled from the respiratory tract. There are two types of cough: the useful and the useless.
Cough is useful when it effectively expels secretions or foreign material from the respiratory tract, i.e. when it is productive; it is useless when it is unproductive and persistent.
Pathophysiology of cough: Cough is caused by the following mechanism.
Deep inspiration, following this, the glottis closes temporarily. This increases the intrathoracic pressure. Later there is forceful expiration which opens the glottis suddenly. Now the pulmonary air which is forced through the trachea carries with it the obstructing secretions of the respiratory tract.
Treatment:
1. Pharyngeal demulcents:
Eg: Syrups, Lozenges, Linctuses, and Liquorices
2. Expectorants:
a. Direct expectorants:
Eg: Balsam of tolu, vasaka, Guaiacol
b. Reflex expectorants:
Eg: Ammonium chloride, Potassium iodide
c.Mucolytics:
Eg: Acetyl cysteine, Carbocystiene, Bromohexine, Ambroxol
3. Antitussives:
a. Opioids:
Eg: Codeine, pholcodeine
b. Non Opioids:
Eg: Noscapine, Dextromethorphan
c.Antihistamines:
Eg: Chlorpheniramine, Diphenhydramine, Promethazine
Pharyngeal demulcents: They produce a smooth coating over the pharyngeal mucosa. This effect is produced directly by the flow of saliva. Sp they reduce the afferent impulses arising from the irritated pharyngeal mucosa. They are useful in symptomatic relief of dry cough.
Expectorants: This are also called as mucokinetics. These are the agents who increase respiratory tract secretions and liquefy them.
Reflex expectorants: These drugs produce mild irritation of the gastric mucosa which stimulates gastric reflexes. This helps to increase the respiratory secretions.
Mucolytics: These are the drugs which decrease the viscosity of the sputum.
Antitussives: These drugs act on the central nervous system. They reduce the tussal impulses by raising the threshold of cough centre. These are used to treat the dry unproductive cough.
Cough, expectorant, mucolytics
