Cough is physiologically useful protective reflex
accumulated mucus and foreign substances.
It occurs due to stimulation of mechano / chemo
receptors in throat, respiratory passage or
stretch receptors in the lung.
Types of cough
Cough is 2 types
Non Productive (Dry)
Mechanism of cough
Stimulation of mechano or chemoreceptors
(throat, respiratory passages or stretch receptors in
Afferent impulses to cough centre (medulla)
Efferent impulses via parasympathetic & motor
nerves to diaphragm, intercostal muscles & lung
Increased contraction of diaghramatic, abdominal &
intercostal (ribs) muscles ⇒noisy expiration
Most common causes of cough
Upper/lower respiratory tract infection
Congestive heart failure
Use of drugs (e.g.:ACEI)
Classification of drugs
Demulcents:- These are indirect peripherally
acting cough suppressants.
• They provide a protective coat over
sensory receptors on pharynx and reduce
afferent impulses from the inflamed /
• They provide relief in dry cough arising
• Ex:- Honey, liquorice
• Mucokinetics:- These expectorants
stimulate the flow of respiratory tract
secretions by stimulating bronchial
secretory cells( to inc. volume) and the
ciliary movement (to facilitate their
Ex:- Volatile oils, certain emetics in sub
emetic doses, ammonium chloride, Na
citrate, guaiacol and guaifenesin.
• Essential oils:- Provide only mild expectoration
by directly stimulating the bronchial secretory
• Syrup of Ipecacuanha know its use has
• Sodium and potassium citrate:- (0.3-1g) After
absorption citrates get converted to
bicarbonates in vivo and mucus becomes less
viscous in alkaline pH.
• Ammonium chloride:- It is a gastric irritant which
reflexly enhances bronchial secretions.
• Large doses-produce metabolic acidosis.
KI:- (0.2-0.3g) It is secreted by bronchial
glands and in this process irritates them,
increasing the volume of secretions.
• It also gastric irritant acts reflexly as well.
A/E:-It is dangerous in pts sensitive to iodine,
and interfere with thyroid function.
• Prolong use - induce goiter and
• Less popular now because of these
• Guaiacol and Guaifenesin - obtained from
creosote wood but nowadays are prepared
• These safe expectorants with proven efficacy.
• Guaifenesin is less irritating derivate of guaiacol.
• After absorption, guaifenesin is secreted
through bronchial glands to increase airway
secretion and mucosal ciliary activity.
• Admi orally 100-200mg BD
• Mucolytics alter the chemical
characteristics of mucus to ↓ its viscosity
and facilitate its removal by ciliary action
• Commonly used mucolytics include acetyl
ambroxol and dornase-alfa.
Bromhexine:- Alkaloid from vasaka plant .
• It depolymerises mucopolysaccharides of
mucus directly and also by ↑ lysosomal
enzyme activity that break the fiber
network of tenacious sputum .
• Oral dose is 8-16mg TDS
S/E:- GIT upset and rhinorrhoea
• Ambroxol:-Metabolite of bromhexine and
has a similar mode of action
• Oral dose 30mg BD/TDS
Acetylcyseteine :- It is a mucolytic that ↓
viscosity of mucus by splitting the
disulfide –S-S- bonds of mucoproteins.
• It’s action facilitated by alkaline pH(7-9)
• Admi is done by nebulisation (3-5ml of
20%solution),also oral 200mg TDS but
efficacy is much less.
• S/E :- N, V, stomatitis and bronchospasam
Dornase-alfa:- It is highly purified solution of
recombinant human deoxyribonuclease
(DNase). These enzyme that selectively
• Purulent (Pus) pulmonary secretions in
cystic fibrosis contain very high amounts
of extra cellular DNA.
• Dornase alfa inhalation (2.5mg once daily)
hydrolysis this accumulated DNA in the
sputum of the pts of cystic fibrosis
• Drinking warm water, inhaling warm moist
air or menthol vapours, surfactants such
as tyloxapol, proteolytic enzymes such as
chymotrypsin or trypsin are also used for
their hydrating and mucolytic action.
• Act in the CNS to raise the threshold of
cough centre to reduce tussal impulses
• Main aim to control rather then eliminate
• These are mainly useful for dry cough or if
cough is disturbs sleep or is hazardous.
Codeine:- An opium alkaloid (Semi
synthetic opioid), qualitatively similar to but
less potent then morphine.
• It is more selective for cough centre and it
is treated as standard antitussive.
• It suppress cough center for 6hr.
• Admi orally (10mg BD or TDS)
• Abuse liability is low at these dose.
S/E:- High dose cause respiratory
depression, convulsions, postural
Pholcodeine:- It is structurally related to
codeine but it is slightly more potent,
longer acting and better tolerated than
• It cause lesser constipation and
drowsiness than codeine.
• More suited for long term use
• Orally 10-15mg BD
Dextromethorphan:-It is methyl ester of the
dextroisomer of levorphanol.
• Less addition liability, no analgesic action,
least constipating effect, minimal
• It is as potent as codeine and given orally
• Most popular cough suppressant
• Combination available with antihistamines
and bronchodilators in cough mixtures.
Noscapine:- It is naturally occurring opium
alkaloid belonging to benzylisoquinoline
• Popular cough suppressant
• Given orally 15mg TDS.
• Less addiction liability, drowsiness,
S/E: At high doses may produce N, H and
Pipazethate:- Phenothiazine group of
antitussive .Occasionally used in cough
• Given orally 40mg TDS
Chlophedianol:- It is less effective
• Rarely used
• Dose 20mg BD orally
• High doses cause excitatory effects,
Centrally as well as peripherally
Benzonatate:- It is structurally related to LA
• It not only inhibits the afferent cough
impulses to suppress the central cough
center, but also inhibits the pulmonary
stretch receptors and also posses local
• Administered orally 100-200mg
S/E: D, N, H
• High doses cause vertigo.
Specific treatment approach to
Etiology of cough
1) Upper/lower respiratory
2) Smoking/chronic bronchitis
Cessation of smoking
3) Pulmonary tuberculosis
4) Asthmatic cough
5) Postnasal drip (sinusitis)
Antibiotics, nasal decongestants, antihistamines
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