Cough suppressants can be expectorants, anti-tussives, or pharyngeal demulcents. Expectorants work to increase or thin bronchial secretions to facilitate their removal through coughing. Common expectorants include guaifenesin, ammonium salts, and bromhexine. Bromhexine works by reducing the viscosity of thick sputum. Carbocisteine is another mucolytic agent that liquefies viscid sputum by opening disulfide bonds in mucoproteins. Both bromhexine and carbocisteine are used to treat chronic asthma, bronchitis, and other respiratory conditions involving excessive mucus.

2. COUGH-SUPPRESSANTS
Cough is a protective reflex. It expels secretions or foreign particles from air passages. It occurs due to stimulation of mechano, chemo receptors of throat,
respiratory tract and stretch receptors in lungs. It is of two types-
(1) Non-productive cough or useless cough or cough without sputum
(2) Productive cough or useful cough or cough with sputum
Factors responsible for producing cough
1. Irritants
2. Pollutants
3. Dust
4. Smoke
5. Upper respiratory infections
6. Foreign particles
7. Drugs and chemicals
8. Pathophysiological conditions-
a. Asthma
b. Lung cancer
c. Tuberculosis
d. Pleural infections
e. Chronic bronchitis
Drug therapy for Cough
Classification of Drugs
(I) Expectorants
(II) Anti-tussives
(III) Pharyngeal demulcents
Expectorants-
They are also known as mucokinetics and increase bronchial secretions or reduce its viscosity and facilitate its removal by coughing.
(A) Directly acting
Benzoin
Guaiacol
Guaiphenesin or glyceryl guaiacolate
Potassium acetate
Potassium citrate
Potassium iodide
Sodium acetate
Sodium citrate
Terpen hydrate
Tolu balsam
Vasaka

3. (B) Reflexly acting (they stimulates reflexes that help to increases respiratory & bronchial secretions. They are also known as saline
expectorants)
• Ammonium carbonate
• Ammonium chloride
• Potassium iodide
• Ipecacuhana (Ipecac)
• Tincture of scilla
(C) Mucolytics (they reduces viscosity of tenacious sputum by breaking the fiber network by liberating lysosomal enzymes or by
depolymerization of mucopolysaccharides)
• Acetyl cysteine
• Methycesteine
• Bromhexine
• Carbocysteine
• Erdosteine
• Dornase-alpha
• Hypertonic sodium chloride (3-5% solution)
• Mesna
(D) Miscellaneous agents
These agents are effective in treatment of cough associated with bronchospasm and cough due to infections of lungs.
• Antihistaminics
• Anti-infectives
• Tranquillizers
• Volatile oils-
• Eucalyptus oil
• Anise oil
• Lemon oil
• Bronchodilators-
• Salbutamol
• Orciprenaline
• Isoprenaline
• Ephedrine
• Local anaesthetics

4. PROTOTYPE DRUGS
GUAIPHENESIN OR GLYCERYL GUAIACOLATE
It is a bark extract of creosote, useful in the treatment of productive cough.
Mechanism of action-Looses mucus, thins bronchial secretions and enhancing mucosal ciliary action.
Dose
100-300mg/TDS
Adverse effects-GIT upsets, Nausea, Vomiting and Drowsiness.
Uses
It is preferred in the following cases-
 Chronic cough
 Excessive bronchial secretions
AMMONIUM SALTS
They causes gastric irritation and used in various anticough preparations.
Mechanism of action
Reflexly enhancing bronchial secretion and sweating.
Dose
0.3-1gm in various preparations
Adverse effects-Nausea and Unpleasant taste
Uses
They are preferred in following cases-
 Productive cough
BROMHEXINE
It is a derivative of vasicine, obtained from the plant of adhatoda vasaca.
Mechanism of action-Reduce viscosity of tenacious sputum by broken the fibers network by liberating lysosomal enzymes or by depolymerization of
mucopolysaccharides.
Contra-indicated in-
Peptic ulceration
Dose
8mg/TDS/orally
Adverse effects-Rhinorrhoea, Lacrymaton, GIT irritation and Rashes
Uses
It is preferred in following cases-
 Chronic asthma
 Bronchitis
 Bronchiectasis

5. CARBOCISTEINE
It is a derivative of L-cysteine, mucolytic agent, liquefies viscid sputum, useful in coughing as expectorant, and facilitates mucociliary
clearance and expectoration by reducing sputum viscosity.
Pharmacological actions
It reduces viscosity and increase the volume of sputum
Mechanism of action
Opens disulphide bonds in mucoproteins present in sputum
ADME
Administered orally
Precautions
First trimester of pregnancy
Contra-indicated in-
Peptic ulceration
First trimester of pregnancy
Dose
250-750mg/TDS or QID
Adverse effects
• Nausea
• Vomiting
• Stamititis
• Bronchospasm
• GIT irritations
• Rashes
Uses
It is preferred in the following cases-
 Coughing as expectorants
 Chronic asthma
 Bronchitis
 Bronchiectasis
 Cystic fibrosis
 Sinusitis