DRUGS FOR COUGH

Dr.Vijay Bhushanam

Cough (Introduction)

• Cough is an explosive expiration, that provides a normal protective mechanism for clearing the tracheo-bronchial tree of secretions and foreign material.

• When excessive or bothersome, it is also one of the most common symptoms for which patients seek medical attention.

• Reasons for this include discomfort from the cough itself, interference with normal lifestyle, and concern for the cause of the cough, especially fear of cancer.

Mechanism of cough

• Coughing may be initiated either voluntarily or reflexively.

• As a defensive reflex it has both afferent and efferent pathways.

• The afferent limb includes receptors within the sensory distribution of the trigeminal, glossopharyngeal, superior laryngeal and vagus nerves.

• The efferent limb includes the recurrent laryngeal nerve and the spinal nerves.

Mechanism of cough (Cont.)

• Deep inspiration glottic closure relaxation of the diaphragm muscle contraction against a closed glottis markedly positive intrathoracic pressure narrowing of the trachea glottis opens at once the large pressure differential between the airways and the atmosphere coupled with tracheal narrowing produces rapid flow rates through the trachea COUGH

• The shearing forces that develop aid in the elimination of mucus and foreign materials.

Etiology of Cough

• The most common causes of cough can be categorized according to the duration of the cough.

• Acute cough (<3 weeks): URTIs (especially the common cold, acute bacterial sinusitis, and pertussis), pneumonia, pulmonary embolus, and congestive heart failure.

• Sub-acute cough (3-8 weeks): post-infectious• Chronic cough (>8 weeks):

In a smoker: chronic obstructive lung disease or bronchogenic carcinoma.

In a nonsmoker: postnasal drip (sometimes termed the upper airway cough syndrome), asthma, and gastroesophageal reflux.

Types of Cough

• Non-productive (dry): No useful purpose, increases discomfort to the patient needs suppression

• Productive (tenacious): Presence of excessive sputum suppression not desired needs coughing/clearing out of the sputum

Classification of drugs for Cough

• Pharyngeal demulcents: Lozenges, cough drops, linctuses containing syrup, Glycerine, Liquorice

• Expectorants:

1. Mucokinetics (Bronchial secretion enhancers): Sodium or potassium citrate, Potassium iodide, Guaphenisin (Glyeryl guaiacolate), balsum of Tolu, Vasaka, Ammonium chloride.

2. Mucolytics: Bromhexene, Ambroxol, Acetylcystein, Carbocystein

• Antitussives (Cough center supressants):

a) Opioids: Codein, Pholcodein

b) Non-opioids: Noscapine, Dextromethorphan, Chlophedianol

c) Antihistaminics:Chlorpheniramine, Diphenhydramine, Promethazine

• Adjuvant antitussives:

Bronchodilators: Salbutamol, Terbutaline

Pharyngeal demulcents

• Sooth the throat and reduce afferent impulses from the inflamed/irritated pharyngeal mucosa.

• E.g: Lozenges, cough drops, linctuses containing syrup, Glycerine, Liquorice

Expectorants

• Increase bronchial secretions or reduce its viscosity, facilitating its removal by coughing

• E.g:• Mucokinetics (Bronchial secretion enhancers): Sodium or

potassium citrate, Potassium iodide, Guaphenisin (Glyeryl guaiacolate), balsum of Tolu, Vasaka, Ammonium chloride.

• Mucolytics: Bromhexene, Ambroxol, Acetylcystein, Carbocystein

Antitussives (Cough center supressants)

• These act – in CNS to raise the threshold of cough center (and/or)– peripherally in Respiratory tract to reduce tussal impulse

• Should be used only for dry unproductive cough (or) • if the cough is unduly tiring, disturbs sleep (or) • is hazardous (hernia, piles, cardiac ds., ocular surgery etc)• E.g: • Opioids: Codein, Pholcodein• Non-opioids: Noscapine, Dextromethorphan,

Chlophedianol• Antihistaminics: Chlorpheniramine, Diphenhydramine,

Promethazine

Bronchodilators

• Bronchospasm can induce/aggravate cough, especially in individuals with bronchial hyperreactivity

• Bronchodilators relieve cough in such individuals• Improve the effectiveness of cough in clearing

secretions by increasing the surface velocity of airflow during cough

• E.g: Salbutamol, Terbutalin

Antitussive/ExpectorantCombinations

• AMBRODYL PLUS: Ambroxol, Chlorpheniramine, Salbutamol, Guaphenesin.

• ASTHALIN: Salbutamol, Guaphenesin.• ASCORIL-C: Codeine, Chlorpheniramine.• BENADRYL: Diphenhydramine, Ammonium chloride,

Sodium citrate, Menthol.• GRILINCTUS: Dextromethorphan, Chlorpheniramine,

Guaphenesin, ammonium chloride.

Specific Rx for cough

• URTI/LRTI Appropriate antibiotics• Smoking/Chr. Bronchitis Cessation of smoking/

avoidance of pollutants• PTB ATT• Post nasal drip due to sinusitis Antibiotics/Nasal

decongestants/H1 antihistaminics

• Postnasal drip due to allergy Avoidance of precipitating factors/Corticosteroid nasal spray/H1 antihistaminics

• GERD H2 blockers/PPIs/Cisapride• ACE inhibitor induced cough Switch to ARBs/CCBs

• Asthmatic cough Inhaled β2

agonists/Ipratropium/Corticosteroids

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