This document discusses different types and classifications of cough medications. It describes demulcents which soothe the throat, expectorants which increase bronchial secretions or reduce viscosity, and mucolytics which break down mucus. It also discusses antitussives which suppress the cough center or act peripherally, including opioids, nonopioids, antihistamines, and prenoxdiazine. Bronchodilators are described as adjuvant antitussives by improving airflow during coughing.

1. COUGH

2. Introduction:
a protective reflex meant for expulsion of respiratory secretions or
foreign particles from air passages
due to stimulation of:
• mechano- or chemoreceptors in throat/ respiratory passages or
• stretch receptors in the lungs
Two types:
• Useless cough(non productive)
• Useful cough(productive)

3. Classification of drugs:
1. Pharyngeal demulcents:
Lozenges, cough drops, linctuses containing syrup, glycerine, liquorice.
2. Expectorants (Mucokinetics):
(a) Bronchial secretion enhancers:
Sodium or Potassium citrate, Potassium iodide, Guaiphenesin
(Glyceryl guaiacolate), balsum of Tolu, Vasaka, Ammonium chloride.
(b) Mucolytics:
Bromhexine, Ambroxol, Acetyl cysteine, Carbocisteine

4. 3. Antitussives (Cough centre suppressants):
(a) Opioids:
Codeine, Ethylmorphine, Pholcodeine.
(b) Nonopioids:
Noscapine, Dextromethorphan, Chlophedianol.
(c) Antihistamines:
Chlorpheniramine, Diphenhydramine, Promethazine.
(d) Peripherally acting:
Prenoxdiazine.
4. Adjuvant antitussives:
Bronchodilators: Salbutamol, Terbutalin.

5. DEMULCENTS AND EXPECTORANTS:
Demulcents: Sooth the throat and reduce afferent impulses from
pharyngeal mucosa
Expectorants (Mucokinetics) : increase bronchial secretion or reduce
its viscosity
 Sodium and potassium citrate: increase bronchial secretion by salt
action
 Potassium iodide: irritate the airway mucosa(can affect thyroid
function)

6.  Guaiphenesin, vasaka, tolu balsum:
 Plant products
 Enhance bronchial secretion
 Increase mucociliary function
 Ammonium salts: reflexly increase respiratory secretions
US-FDA has stopped marketing of all expectorants, except
guaiphenesin
Steam inhalation and proper hydration may be more helpful in
clearing airway mucus

7. MUCOLYTICS:
Bromhexine:
derivative of Adhatoda vasica (Vasaka)
depolymerises mucopolysaccharides directly as well as by liberating
lysosomal enzymes
useful if mucus plugs are present
Side effects:
rhinorrhoea and lacrimation, nausea, gastric irritation, hypersensitivity

8. Ambroxol:
metabolite of bromhexine
Acetylcysteine:
opens disulfide bonds in mucoproteins present in sputum
has to be administered directly into the respiratory tract
Carbocisteine:
MOA similar to acetylcysteine
Administered orally(250–750 mg TDS)
may break gastric mucosal barrier : contraindicated in peptic ulcer
patients

9. ANTITUSSIVES:
MOA:
• act in the CNS to raise the threshold of cough centre or
• act peripherally in the respiratory tract to reduce tussal impulses
• or both
Used in:
• dry nonproductive cough
• cough is unduly tiring, disturbs sleep or
• Is hazardous(hernia, piles, cardiac disease, ocular surgery)

10. Opioids:
Codeine:
Qualitatively similar to and less potent than morphine
more selective for cough centre
Suppresses cough for about 6 hours(standard antitussive)
Antagonised by naloxone
Abuse liability is low(still present)
Side effect:
Constipation(m/c), respiratory depression and drowsiness

11. Ethylmorphine:
similar & less constipating than codein
Pholcodeine:
no analgesic or addicting property
similar in efficacy to codeine
Longer acting

12. NONOPIOIDS:
Noscapine (Narcotine):
An opium alkaloid of the benzoisoquinoline series
no narcotic, analgesic or dependence inducing properties
nearly equipotent to codeine
useful in spasmodic cough
can release histamine and produce bronchoconstriction in asthmatics
Side effects:
Headache and nausea

13. Dextromethorphan:
synthetic central NMDA (N-methyl D-aspartate) receptor antagonist
d-isomer is antitussive while l-isomer is analgesic
does not depress mucociliary function
devoid of constipating action
Antitussive action: equivalent to codein
Side effect:
 Dizziness, nausea, drowsiness.
 hallucinations and ataxia at high doses

14. ANTIHISTAMINES:
Used for sedative and anticholinergic action
Not selective for cough centre
May reduce secreations
Useful for cough in respiratory allergic states
Commonly used drugs:
 Chlorpheniramine (2–5 mg),
 Diphenhydramine(15–25 mg)
 Promethazine (15–25 mg

15. PERIPHERALLY ACTING ANTITUSSIVES:
Prenoxdiazine:
desensitizes the pulmonary stretch receptors and reduces tussal
impulses originating in the lungs
indicated in cough of bronchial origin
Efficacy is not good enough

16. BRONCHODILATORS:
Bronchospasm can induce or aggravate cough
Pulmonary receptors stimulation(in bronchial hyperactivity) can
trigger both
Cough &
Bronchoconstriction
Bronchodilators improve the velocity of airflow during coughing