14drugs acting on respiratory system expectorants, respiratory stimulants
Antitussives and expectorants
• Cough is a protective reflex that removes
foreign material and secretions from the
bronchi and bronchioles.
• Coughing may be initiated either voluntarily or
• Two types :
– Productive cough( useful cough)
– Unproductive cough ( useless cough)
a. Opiods and related drugs
Sodium and potassium salts of iodine ,
citric acid or acetic acid , guaicol, tolu
balsam, terpene hydrate, Guaiphenesin
b. Reflexly acting :
Saline expectorants : NH4Cl, NaHCO3
c. Mucolytics :
Pharyngeal demulcents :
Lozenges, cough drops , linctuses
containing syrup, glycerine , liquorice
Specific treatment approach of cough
• Upper respiratory infection:
• Smoking / chronic bronchitis : cessation of
smoking , avoidance of pollutants
• Pulmonary tuberculosis : antitubercular drugs
• Asthmatic cough: antiasthmatics
• Postnasal drip due to sinusitis : antibiotic , nasal
decongestants , H1 blockers
• Gastroesophageal reflux : bed head elevation,
light dinner , diet modification , drugs for PUD
• ACE inhibitor associated cough: substitute by
losartan, indomethacin , nifedipine
1 . MORPHINE
• It is an effective antitussive but it
produces depression of
respiratory centre and drug
dependence .Hence it is not used
at clinical level for antitussive.
2. CODEINE PHOSPHATE
• It is centrally acting cough
MECHANISM OF ACTION
• Depresses cough reflex by a
direct depressant effect on cough
• Used for dry and painful cough.
• Standard narcotic antitussive
• Severe pain
In case of liver disease ,increased
dose causes convulsions in
• Prostatic hypertrophy
• Hepatic disease
• In bronchial asthma because it
• Children below 2 year
Mild to moderate pain
Adult dose ::30-60mg every 4
hours ,to a maximum of
Child dose:1-12 years:3mg/kg
daily in divided doses
Dry or painful cough
Adult dose:15-30mg 3-4 times
child dose:7.5-15mg 3-4 times
• It is semisynthetic derivative of codeine.
• It is It is available as linctus and may be given to children ..It
doesnot cause constipation and less liable to cause addiction as
compared to codeine.
• It is more potent than codeine .
MECHANISM OF ACTIONS
• Same as codeine
• For dry and painful cough.
• The antitussive activity of the drug is about equal to that of codeine.the
drug produces no analgesia or addiction or CNS depression.And is also
devoid of constipating actions.
MECHANISM OF ACTION
• Acts centrally to elevate the threshold for coughing.
• Widely used anti tussive and is the constituent of many cough remedies.
• Used for dry cough
It occasionally causes
• Mental confusion
• GI disturbances
• Liver disease
• 10-20mg every 4hrs or 30mg every 6-8hrs
• It is as effective as codeine.
• It has weak bronchodilator properties and stimulates the respiration.
• IT is available as linctus and effect last for 4 hrs.It has no addicting,sedative
and analgesic properties.
Drowsiness and nausea
• Many H1 antihistamines have been added to
antitussive/expectorant formulations .They afford
relief in cough due to their sedative and
anticholinergic actions but lack selectivity for the
cough centre.They have no expectorant
action,may even reduces secretions by
anticholinergic actions.They have been specially
promoted for cough in respiratory allergic states .
These are the drugs that facilitate removal of respiratory secretions by
Mechanism of actions
• They soothe inflamed respiratory mucosa by stimulating protective
mucus secretions from secretory cells of respiratory airways.
• Increase fluidity of sputum ,that helps in its expectoration by cough.
• Stimulates healing and repair of chronically inflamed respiratory
• These act on the cholinergic
receptors of the bronchi and
increases bronchial secretions.these
are not used clinically due to strong
Decrease heart rate
Decrease force of contraction
Sodium and potassium salts of iodine
• KI is active in increasing the volume
and decreasing the viscosity of
bronchial secretion. Being a bronchial
gland irritant as well as gastric
Irritant ,it directly and reflexly
increases the bronchial secretions.
• Unpleasant taste
• Sneezing and conjuctival irritation
resembling common cold
• Skin rashes
• Goiter and hypothyroidism
MECHANISM OF ACTION
All these drugs except water
irritate the gastric mucosa
.Impulses goes to the vomiting
centre and from there
impulses are sent to
bronchioles and bronchial
Ammonium salts: 0.3-1gm
• Bromhexine is a mucolytic agent used in the treatment of respiratory
disorders associated with viscid or excessive mucus
• It reduces viscosity of bronchial secretions by depolymerization of
mucopolysaccharides in ground substances of bronchial secretions and
by liberating lysosomal enzymes resulting in thinning of the mucus.
• Derived from Adhatoda vasica
1.to reduce sputum viscosity in cystic fibrosis
2.chronic asthma and bronchitis
adult 8mg TDS
adult -750mg TDS initially
1.5 g daily in divided doses
Rhinorrhoea,lacrimation,skin rashes, GI irritation
MECHANISM OF ACTIONS
They suppress cough reflex by decreasing the input of stimuli from
cough receptors in respiratory passages.
They glutinously and soothingly coat pharynx.
steam inhalation with tincture benzoin or menthol promotes
secretion of protective mucus.
3.DRUGS WITH LOCAL ANAESTHETIC ACTIVTY
Benzonatate reduce cough by depressing pulmonary stretch
receptors.It also has a central cough suppressant effect.
Demulcents :cough due to sore-throat and pharyngitis
Steam inhalation :cough due to tracheo bronchitis.
Respiratory stimulants/ analeptics
• Stimulate respiration and have resuscitative value in
coma or fainting.
• Situations in which analeptics are used :
Respiratory depression due to Hypnotic drug poisoning
Suffocation on drowning
Apnoea in premature infants
Failure to ventilate spontaneously after general anesthesia
• Drugs :
Reflex stimulants : ammonia, alcohol vapours
• Mechanism of action
– Acts by promoting excitation of central neurons , at low dose more selective
for respiratory centre
– Increases depth of respirations (tidal volume) by stimulating respiratory
center in CNS; respiratory rate may increase slightly.
– May elevate BP by increasing cardiac output, due to stimulation of carotid
and aortic body chemoreceptors
– Respiratory depression from opiates is reversed without affecting pain relief.
– Reversal of respiratory depression caused by anesthesia (other than muscle
relaxants) or drug overdose;
– temporary measure for acute respiratory failure in patients with COPD who
are not undergoing mechanical ventilation.
– Low doses of doxapram have been used in the treatment of apnea of
prematurity when methylxanthines have failed.
• Adverse Reactions
– Arrhythmias; tachycardia; increased BP; tightness in chest;
chest pain; phlebitis.
– Seizures; paresthesia; increased reflexes; disorientation;
dizziness; involuntary movements.
– Nausea; vomiting; diarrhea; desire to defecate.
– Urinary incontinence and retention; elevation of BUN.
– Hemolysis (with rapid infusion).
– Laryngospasm; bronchospasm; rebound hypoventilation; cough;
– Flushing; feelings of warmth; sweating
– Doxapram contains benzyl alcohol, which has been associated
with fatal “gasping syndrome” in premature infants.
Route / dosage:
• Bolus IV injection 0.5 to 1 mg/kg (single dose not
to exceed 1.5 mg/kg). Can be given as multiple IV
injections q 5 min (not to exceed total dose of 2
• IV infusion Initial rate: 5 mg/min until satisfactory
respiratory response is noted. Maintenance rate:
1 to 3 mg/min. Maximum total infusion dose is 4