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Pharmacology of cough

This presentation covers focuses on cough pharmacology (productive and non productive cough) specifically mnade for undergraduate pharmacy students

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Pharmacology of cough

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  1. Pharmacology of cough ROBERT TUMWINE DPHARM, GCP, BME(MUK)

  2. Cough • Cough is a protective reflex of the respiratory system that helps clear the airways of irritants, secretions, or foreign material. Functions of Cough • Clears mucus, dust, microorganisms • Protects lungs from aspiration(inhalation of foreign substances or objects) • Maintains airway patency( ability of the airway to remain open for adequate air to flow in and out if the respiratory system

  3. Types of cough • Productivecough (useful cough) • cough that expels sputum or mucus from the respiratory tract. • It occurs when there is excess mucus production (e.g., in infections, chronic bronchitis, COPD, pneumonia). • Non productive/ dry cough (useless cough) • cough without sputum or mucus production. • It often results from airway irritation or inflammation rather than excess secretions • Can be persistent and irritating.

  4. Classification of Cough drugs • Antitussives are drugs used to suppress the intensity and frequency of coughing • Two types; • Central antitussives • Suppress the medullary cough centre and may be divided into two groups • Opioid antitussive e.g. codeine, hydrocodeine, pholcodeineetc • Non opioid antitussives e.g. dextromethorphan, noscapine

  5. Peripheral antitussives • Decrease the input of stimuli from the cough receptor in the respiratory passage for example, Demulcents e.g. lozenges, honey Note: • Used mainly for non-productive (dry) cough

  6. Expectorants • Direct acting; guanphenesin, sodium citrate • Indirect acting; ammonium salt, ipecac Mucolytics • bromhexine, ambroxol, acetlcysteine, methylcysteine Others; • Antihistamine, bronchodilators and local anesthetic

  7. Opioid Antitussives • Examples: Codeine, Pholcodine, Hydrocodone. • Mechanism of action • Act on μ-opioid receptors in medulla → suppress cough reflex. • Side effects: Sedation, constipation, dry mouth, respiratory depression (high doses), risk of dependence. • Uses: Dry cough, severe irritating cough Note: Codeine is a narcotic relatively less addicting drug and central antitussive agent

  8. Non-Opioid Antitussives Examples: Dextromethorphan, Noscapine, Butamirate, Benzonatate. Mechanism: Dextromethorphan – NMDA receptor antagonist, suppresses medullary cough center. Uses: Non-productive cough, safer in children and elderly. Side effects; nausea, vomiting Advantages: Less sedation, little/no addiction risk.

  9. Mucolytics (Mucus-thinning drugs) • Examples: Acetylcysteine, Bromhexine, Ambroxol, Carbocisteine, methycysteine • Mechanism: Breaks disulphide bonds in mucus glycoproteins → reduces viscosity. • Uses: COPD, cystic fibrosis, bronchiectasis, pneumonia. • Side effects : GIT irritation, nausea and vomiting Note; they are Used when mucus is thick and sticky, making clearance difficult.

  10. Expectorants (Mucokinetics) • Examples: Guaifenesin, Ammonium salts, Potassium iodide,Ipecac, saline expectorant, sodium citrate • Expectorant is a drug that aid in removing thick mucus from respiratory passages, They increase bronchial secretiontherefore helping to expel mucus • Used mainly for productive cough. • Uses: Productive cough with thick mucus (bronchitis, COPD).

  11. Decongestants • Examples; phenylephrine, oxymetazoline, Xylometazolineephedrine, pseudoephedrine, • Decongestants are the drugs that reduce congestion of nasal passages, which in turn open clogged nasal passages and enhances drainages of the sinuses. • Side effects; Insomnia, nervousness, hypertension, palpitations

  12. Demulcents (soothing agents) Examples;Lozenges, honey, glycerine • Form a protective coating on pharynx to reduce throat irritation in dry cough. • They are used to sooth the throat • For symptomatic relief in dry cough

  13. Miscellaneous Drugs • Antihistamines (H1 blockers) – e.g., Diphenhydramine, Chlorpheniramine, promethazine • Reduce cough due to allergy or post-nasal drip. • Cause sedation. • Decrease secretions( anticholinergic effect) • Suitable for allergic cough but not for asthma

  14. Bronchodilators Examples : salbutamol, terbutaline • Useful when cough is due to bronchospasm (e.g., asthma, COPD). • Not used routinely for any type of cough • Used only when there is bronchoconstriction

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