protective reflex that clears the
respiratory tract of the accumulated
mucus and foreign substances.
It occurs due to stimulation of mechano /
chemo receptors in throat, respiratory
passage or stretch receptors in the
Types of cough
• Cough is two types
Non Productive (Dry)
• Non productive:- cough is considered as
serving no useful purpose., rather it
increased discomfort to the patient.
• For treatment antitussive agents are
• Productive cough:-It is characterized by
presence of excessive sputum and may be
associated with conditions such as chronic
bronchitis and bronchiectasis.
• In this condition expectorants are useful.
• Ideal antitussive should suppress the
frequency as well as intensity of coughing
with out affecting the normal elimination of
excessive secretions from the respiratory
• Expectorants:- Increase
decrease the viscosity
enhance the propulsion
upward and outward by
the volume and
of secretions to
of the secretion
Classification of drugs
Demulcents:- Indirect peripherally acting
• 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
stimulate the flow of respiratory tract
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 cells.
• know its use has declined.
Sodium and potassium citrate:- (0.3-1g) After
absorption citrates get
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 it can 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.
ADE:-It is dangerous in patients sensitive to
iodine and interfere with thyroid function.
• Prolong use can induce goiter and
• Less popular now because of hazards
• Guaiacol and Guaifenesin are obtained from
creosote wood but nowadays are prepared
• These safe expectorants with proven efficacy.
• Guaifenesin is less irritating derivate of guaiacol.
• After absorption, guaifenesin
through bronchial glands to increase airway
secretion and mucosal ciliary activity.
• It is administered orally 100-200mg BD
Mucolytics alter the chemical characteristics
of mucus to decrease its viscosity and
facilitate its removal by ciliary action
Commonly used mucolytics include acetyl
ambroxol and dornase-alfa.
Bromhexine:- It is an alkaloid from vaska
• It depolymerises mucopolysaccharides of
and also increase lysosomal
enzyme activity that break the fiber
network of tenacious sputum .
• Oral dose is 8-16mg TDS
• Side effects:- GIT upset and rhinorrhoea
(Water release from nose).
• Ambroxol:-Metabolite of bromhexine and
has a similar mode of action
• Oral dose 30mg BD/TDS
Acetylcyseteine :- It is a mucolytic that
decrease the viscosity of mucus by
splitting the disulfide –S -- S- bonds of
• Action facilitated by alkaline pH(7-9)
• Administratation is done by nebulisation
(3-5ml of 20%solution),also oral 200mg
TDS but efficacy is much less.
• Side effects :- Nausea, vomiting, stomatitis
• 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 patients of cystic fibrosis
Drinking warm water, inhaling warm moist air
or menthol vapours, surfactants such as
chymotrypsin or trypsin are also used
their hydrating and mucolytic action.
• Drugs that act in the CNS to raise the
threshold of cough centre to reduce tussal
• Main aim to control rather then eliminate
• These are mainly useful for dry unproductive
cough or if cough is disturbs sleep or is
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.
• Administered orally (10mg BD or TDS)
• Abuse liability is low at these dose.
• Side effects:- High dose cause respiratory
Pholcodeine:- It is structurally related to
codeine but it is slightly more potent,
longer acting and better tolerated than
drowsiness than codeine.
• More suited for long term use
• Orally 10-15mg BD
Dextromethorphan:-It is methyl
dextroisomer of levorphanol.
• It has less addition liability, no analgesic action,
least constipating effect and minimal drowsiness
• It is as potent as codeine and given orally 10mg
• 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,
• Side effect: At high doses may produce
nausea, headache and tremors.
Pipazethate:- Phenothiazine group
antitussive. Occasionally used.
• Given by orally 40mg TDS
Chlophedianol:- It is less effective
• Rarely used
• Dose 20mg BD orally
• High doses cause excitatory
Centrally & peripherally acting antitussives
Benzonatate:- It is structurally related to
local anesthetic tetracaine.
• 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 Orally
Side effects: Drowsiness, nausea, headache
• High doses cause vertigo.