Drug Used in Respiratory System

Cough is a protective reflex which helps to expel irritant matter from the respiratory tract. This is necessary for preventing mechanical obstruction to breathing. Irritation is the chemical or mechanical (Stretch) receptors in the respiratory tract at various sites such as pharynx, larynx, trachea or bronchi produces fussal impulses which are carried out by efferent fibers in the vegus and sympathetic nerves to the cough center located on the medulla oblongata, which initiates the act of coughing. Inturn, the injury to the respiratory mucosa caused by the high expiratory velocity of air during coughing can aggregate bronchospasm.

The cough may be productive or dry cough. Productive cough associated with a large amount of sputum and dry cough is without much sputum.

Environmental irritant may cause cough by irritating the lungs, trachea or bronchi. Smoking cigarettes is a well known cause of chronic persistent cough. Cough due to the inhalation of allergerns such as dust, chemicals and Poland is commonly observed in as asthmatics. The common cause of transient cough is the common cold. Enlarged, infected tonsil, abnormally elongated nasal polyps can also cause chronic persistent cough.

Other important causes of cough are:

  • Upper respiratory tract infections.
  • Acute lug infection, asthma and pleural disease.
  • Chronic pulmonary disease like chronic bronchitis, tuberculosis and lung cancer.
  • Secondary acute left ventricular failure.
  • Drug induced cough, due to administration of captopril, beta blocker, iodides, levodopa etc.

Drug which are used in the symptomatic treatment of cough are classified as follows:

  1. Pharyngeal Demulcent: Lozengas, cough drops, glycerin, liquorice, linctus and syrup.
  2. Expectorrent (Mucokinetics) –
    1. Directly Acting – Sodium and Potassium citrate or acetate, potassium iodide, guaiphenesin, balsam of tola, vasoka.
    2. Reflexly Acting – Ammonium chloride or carbonate, potassium iodide, ipecauanha.
    3. Mucolytics – Bromhexine, acetyl cysteine, carbocisteine.
  3. Antitussive (Cough centre suppressants)
    1. Opiods – Codeine, pholcodeine, morphine, ethyl morphine.
    2. Non opioids – Noscapine, destromethorphan, carbetapentane, oxeladin, chlophedianol, pipazethate.
    3. Antihistamines – Chlorpheniramine, diphenhydramine, promethazine.

Pharyngeal Demulcent:

They smooth the throat directly as well as by promoting salivation and reduce afferent impulses from the inflamed or irritated pharyngeal mucosa, thus provide sympathetic relief in dry cough arising from throat.


Expectorrent are the drugs which increase the production of demulcent respiratory tract fluid that covers and protects the irritated mucosa. These drugs are useful in the treatment of useless cough due to irritation of the respiratory mucosa bellow the epiglottis. It also reduces the viscosity of mucosa and helps removal of substances.

Expectorrent can stimulate the output of respiratory tract fluid either directly or reflexly.

  • Direct stimulation: Certain volatile oil like oil of eucalyptus, anise and lemon when administered orraly or by inhalation with steam, can increase the respiratory secretion by direct action.
  • Reflex Stimulation: These drugs act by stimulation the gastric reflexes which help to increase the respiratory secretion. They produce mild irritation of the gastric mucosa and may produces nausea and sometimes vomiting. These drugs increase bronchial secretion producing a lessviscous sputum, which easily expel. Certain salts which produce such an action are called saline expectorrent.


These are gastric irritation; reflexly enhance bronchial secretion and sweating. Many cough mixture contain these salts. It can cause nausea and even vomiting. The usual dose is 300 mg in a tea spoonful of cough mixture.


Mechanism of Action:

It is the most commonly employed preparation. It acts both directly and reflexes and not only increases the respiratory secretion, but has a reputation for liquefying the thick, viscid fluid. Potassium iodide is generally used in producing cough associated with chronic bronchitis, asthama and emphysema (Decreased respiratory function).


The dug is administered orally in a dose 300mg, T.I.D in a mixture form,  watery solution decomposes on standing liberating iodine.

Adverse Effect:

The adverse effects are iodine characterised by nasal catarrh, conjunctival swelling, edema of eyelids, lacrimation, increased respiratory tract secretion, edema and ulcer of larynx, headache and various types of skin rashes.


Children, pregnancy.


These are the drug used to make the sputum thin and less viscid, so that it can be easily expectorated.


These is a synthetic benzylamine compound of an alkaloid Vasicine obtained from Adhatoda vasica. It can given orraly parenterally and by inhalation. Ambroxol is a active metabolite bromhexine.

Mechanism of Action:

It produces the viscosity of cough by inducing thin copious secretion. It depolymerizes mucopolyseccharides directly as well as by liberating lysosomal enzyme so network of fibers in coherent sputum is broken.


It is particularly useful if mucosa plugs are present.


8 to 10 mg TID

Adverse Effect:

Rhinorrhoea and lacrimation.

Brand Name:


Central Cough Suppressant

These drugs inhibit the cough reflex complex by directly acting on the cough centre in the medulla and are useful in the symptomatic relief of dry irritant cough.

Mechanism of Action:

These depress the cough center in the medulla, resulting in an elevation of the cough threshold. When large doses are used respiratory depression may occur.


It is the d-isomer of codeine analogue methorphan. It does not act through the opioid receptor and hass no analgesic and sedative property.

Adverse Effect:

Excitement, irritation, nausea, confusion, dizziness.


10 mg to 20mg every 6 to 8 hours.

Brand Name:



It is an alkaloid of opium. It is available both as sulphate and phosphate in tablet, elixir or syrup form. It is a very effective antitussive agent.


10 to 15mg orally every 4 to 6 hours.


Bronchial Asthma:

Bronchial Asthma is a clinical syndrome characteristic by paroxysmal dyspnoea and wheeze (breathing with whistling sound) due to increase resistance to flow of air through the narrowed bronchi. Narrowing of the bronchi caused due to infiltration and edema of the bronchial mucosa, spasm of the bronchial smooth muscles and blockage by thickened mucus within the bronchial lumen.

Mast cell (present in lungs) and inflammatory cell recruited as a result of initial reaction produce histamine, protease enzyme, PGs. Theses mediators together constrict bronchial smooth muscle cause mucosal edema, hyperemia (increase blood) and produce viscid secretion, all resulting in reversible air way obstruction. Damage to bronchial epithelium emphasizes the hyperactivity.

Chronic obstruction pulmonary disease

It is a disorder of expiratory air flow limitation that does not fluctuate markedly over long periods of time includes chronic bronchitis, emphysema and peripheral airway disease. It is clearly related to smoking and starts after the age 40. Air way obstruction is largely irreversible.


This is a condition where an acute attack is severe, persistent, does not respond to routine treatment with beta adrenergic stimulants and aminophylline and is accompanied by respiratory insufficiency or failure.

Treatment is directed toward reducing the inflammation as well as reliving bronchospasm.


  1. Hydrocortisone hemisuccinate 100 mg (or equivalent dose of another glucocorticoid) i.v. followed by 100 mg/8 hour infusion.
  2. Nebulized salbutamol + ipratropium bromide intermittent inhalations.
  3. Intermittent huridified oxygen inhalation.
  4. Salbutamol or terbutaline 0.4 mg i.m/s.c may be added.
  5. Treat chest infection with intensive antibiotic therapy.
  6. Correct dehydration and acidosis with saline + sodium bi-carbonate / lactate infusion.

Drugs Used For The Treatment of Asthama:

    1. Sympathomimetics: Adrenaline, Ephedrine, Inprenaline, Orciprenaline, Salbutamol, Terbutaline, Salmeterol.
    2. Methylxanthines: theophylline, Aminophylline, Choline Theophyllinate.
    3. Anticholinergics: Atropine methonitrate, Ipratropium bromide, Tiotropium bromide.
  2. MAST CELL STABILIZERS: Sodiumcromogylate, Ketotifen, Nedocromil.
    1. Systemic – Hydrocortisone, Prednisolones.
    2. Inhalations – Beclomethasone Dipropionate, Budesonide, Flunisolide, Acetonide, Fluticason propionate.


It is a synthetic chromone derivative. It is not a bronchodilator, it does not antagonize the mediators like histamine, serotonin and E.C.F. (extracellular fluid) involved in bronchial asthma, it has no anti-inflammatory activity, but is commonly used in the management of bronchial asthma. Its main action is prophylactic, reducing the incidence and severity of allergic asthmatic attacks.

Mechanism of Action:

Sodium chromoglycate inhibits the release of histamine and SRS-A (slow acting substance of anaphylaxis) from sensitized mast cells, possibly by stabilizing the mast cell membrane. It also prevents exercise induced bronchoconstriction in normal and asthmatic patients, by inhibiting the local release of prostaglandins.


It is not absorbed orally. It has to be administered by inhalation. It is rapidly absorbed from the lungs, and is excreted unchanged in urine and bile.

Adverse Effect:

Throat irritation, nasal congestion, headache, dizziness, arthralgia, bronchospasm, rashes.



Special Precaution:



  1. It is used as a prophylactic is patients with bronchial asthma.
  2. It is used for the treatment of allergic rhinitis.
  3. It is also used for the treatment of chronic allergic conjunctivitis as eye drops.

Dosage Form & Brand Name:

FINTAL inhaler: (1 mg metered dose aerosol) 2 puff 4 times daily.

ALLERCROM (2% eye drop): 1-2 drops in each eye 4-6 times/day.

FINTAL (nasal spray 2%) – 2 squeezes in each nostril QID.


It is an orally active nonchromone prophylactic drug for bronchial asthma and allergic disorders.

Mechanism of Action:

Same as sodium chromoglycate. It has also antihistaminic action.


Ketotifen is absorbed orally.

Adverse Effect:

Sedation, dry mouth, dizziness, nausea and weight gain.


  1. It is used in the prophylaxis of bronchial asthma.
  2. It also produces symptomatic relief in many patients with atopic dermatitis, perennial rhinitis, conjunctivitis, and urticaria and food allergy.


1-2 mg BD.

Brand Name:



This is a stable mixture of theophylline and ethylene diamine.

Mechanism of Action:

It is well absorbed orally, it is distributed in all tissues cross placenta and secreted in milk. Metabolized in liver and excreted by urine.

Adverse Effect:

Nausea, vomiting, abdominal pain, insomnia, anxiety and restlessness.


  1. It is used for the treatment of asthma by producing bronchodilation.
  2. It is also used for the treatment of chronic obstructive pulmonary disease (COPD).


Hypersensitivity to Xanthine group.

Special Precautions:

Pregnancy, cardiac and hepatic diseases.


250-500 mg orally/day.

Brand Name:



This halogenated glucocorticoid ester is used in a pressurized metered dose inhaler (MDI). This is life-saling in an acute attack or status asthmaticus.

Mechanism of Action:

Probably all the glucocorticoids (beclomethasone, budesonide) are function as non-specific anti-inflammatory agents to provide relief from congestion and exudation. They act locally on the respiratory mucosa.


Highly effective locally but poorly absorbed, on oral administration largely inactivated by liver due to first pass metabolism.


It is useful for suppressing the asthma.

Adverse Effect:

Hoarseness of voice, dysphonia (speech disorder), sore throat, symptomatic oropharyngeal candidiasis.


2 puffs (100 mg), 3-4 times daily.

Brand Name:

BECLATE inhaler, BECLATE rotacaps, AEROCOT inhaler.


Nasal decongestion can be produced by sympathomimetic drugs which act on alpha receptors. These drugs produce vasoconstriction and shirking of nasal mucosa. They constrict the dilated blood vessels in the nasal mucosa and help to reduce the local edema.

The drugs which are used as nasal decongestants are Ephedrine 05%, Phenylephrine 0.25%, Naphazoline 0.05%, Oxymetazoline 0.05% and xylometazoline hydrochloride 0.1% w/v.

Mechanism of Action:

These drugs increase the nasal potency, lower nasal resistance and provide subjective relief of nasal symptoms. Thus, they provide temporary relief of nasal symptoms in patients with common cold, allergic rhinitis and other respiratory infections.

Adverse Effect:

Insomnia, irritation, local discomfort, burning, stinging, dryness of the mucosa.


Instill 2-3 drops into each nostril.


Pregnancy, glaucoma.

Special Precautions:

Hypotension, CNS depression.

Brand Name:

ORTICARE | XYBEL | NAZIN (Xylometazoline hydrochloride) | NASA-A | METZOL | NAIVION | NASIVION PAED (oxymtazoline) | DRISTAN NASAL DROPS (Phelephrine) | ENDRINE MILD (ephedrine 0.5%)


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