Healthcare in India

Drugs for Cough and Bronchial Asthma

Cough is a protective reflex, its purpose being expulsion of respiratory secretions or foreign particles from air passages. It occurs due to stimulation of mechano- or chemoreceptors in throat, respiratory passages or stretch receptors in the lungs. Cough may be useful or useless. Useless (nonproductive) cough should be suppressed. Useful (productive) cough serves to drain the airway, its suppression is not desirable, may even be harmful, except it the amount of expectoration achieved is small compared to the effort of continuous coughing. Apart from specific remedies (antibiotics, etc. see box), cough may be treated as a symptom (nonspecific therapy) with:

  1. Pharyngeal demulcents : Lozenges, cough drops, linctuses containing syrup, glycerine, liquorice.
  2. Expectorants (Mucokinetics)
    1. Bronchial secretion enhancers sodium or Potassium citrate, Potassium iodide, Guaiphenesin (Glyceryl guaiacolate), balsum of Tolu, Vasaka, Ammonium chloride.
    2. Mucolytics Bromhexine, Ambroxol, Acetyl cysteine, Carbocisteine
  3. Antitussives (cough center suppressants)
    1. Opioids Codeine, Pholcodeine.
    2. Nonopioids : Noscapine, Dextromethorphan, Chlophedianol.
    3. Antihistamines Chlorpheniramine, Diphen hydramine, Promethazine.
  4. Adjuvant antitussives

Pharyngeal demulcents sooth the throat and reduce afferent impulses from the inflamed/irritated pharyngeal mucosa, thus provide symptomatic relief in dry cough arising from throat.
Expectorants (Mucokinetics) are drugs  believed to increase bronchial secretion or reduce its viscosity, facilitating its removal by coughing.
Sodium and potassium citrate are considered to increase bronchial secretion by salt action. Potassium iodide is secreted by bronchial glands and can irritate the airway mucosa. Prolonged use can affect thyroid function and produce iodism. It is rarely used now. Guaiphenesin, vasaka, tolu balsum are plant products which are supposed to enhance bronchial secretion and mucociliary function while being secreted by tracheobronchial glands. Ammonium salts are nauseating-reflexly increase respiratory secretions. A variety of expectorant formulations containing an assortment of the above ingredients, often in combination with antitussives/antihistaminics are marketed and briskly promoted, but objective evidence of efficacy of these is non-conclusive.