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Cough suppressants & expectorants

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Cough suppressants & expectorants

  1. 1. Cough suppressants & Expectorants Dr. Parasuraman AIMST UNV, Malaysia.
  2. 2. Cough suppressants & Expectorants • Cough is protective reflex, its purpose being expulsion of respiratory secretions or foreign particles form the lungs and upper airway passages . • Cough may be useful (productive: sputum is coughed up/ drain the airway) or useless (nonproductive/ dry) • Useless cough should be suppressed • Types of cough – Classified based on duration, characters, quality and timing • Acute : Sudden onset/ less than 3 weeks • Sub-acute : 3-8 weeks • Chronic : longer than eight weeks
  3. 3. Mechanism of cough Stimulation of mechano-or chemoreceptors (throat, respiratory passages or stretch receptors in lungs) Afferent impulses to cough center (medulla) Efferent impulses via parasympathetic & motor nerves to diaphragm, intercostal muscles & lung Increased contraction of diaghramatic, abdominal & intercostal (ribs) muscles noisy expiration (cough)
  4. 4. Drugs for cough • Cough can be treated as a symptom (nonspecific therapy) or with specific remedies (antibiotics, etc.) • Nonspecific therapy – Pharyngeal demulcents: Lozenges, cough drops, linctuses containing syrup, glycerine, liquorice. – Expectorants: (a) Directly acting: Sodium and potassium citrate or acetate, potassium iodide, guaiacol, guaiphenesin (glyceryl guaiacolate), balsum of tolu, vasaka and terpin hydrate. (b) Mucolytics: Bromhexine, ambroxol, acetyl cysteine, carbocisteine. (a) Antitussives (Cough center suppressants): (a) Opioids: Codeine, pholcodeine, ethylmorphine, morphine. (b) Nonopioids: Noscarpine, dextromethophan, oxeladin, chlorphedianol. (c) Antihistamines: Chlorpheniramine, diphenhydramine, promethazine.
  5. 5. Demulcents and expectorants • Expectorants: Increase the bronchial secretion or reduce its viscosity- facilitating its removal by coughing. • Sodium citrate or acetate (0.3- 1 g): – Increase bronchial secretion by salt action. • Potassium iodide (0.2- 0.3 g): – Act directly on the bronchial secretory cells and are excreted into the respiratory tract. It is an irritant and increase the volume of secretion. – The irritant action is not desirable if bronchial mucosa is acutely inflamed. – Dangerous in patients sensitive to iodine and interferes with thyroid function test. – Prolonged use can induce goiter and hypothyroidism. • Guaiacol ([Obtained form wood creosote]; 100-200 mg), tolu balsum (0.3- 0.6 g), Vasaka syrup (2-4 ml) and terpin hydrate (0.1-0.3 g) – Directly increase bronchial secretion and mucosal ciliary action – Gastric upset and rash can occur
  6. 6. Demulcents and expectorants • Ammonium salts (o.3-1 g): – Gastric irritants – Reflexly enhance bronchial secretion and sweating – Nauseating because of unpleasant taste
  7. 7. Mucolytics • Bromhexine/ Ambroxol: – Derivative of the alkaloid vasicine obtained from Adhantoda vasica – Potent mucolytic and mucokinetic, capable of inducing thin copious bronchial secretion – dissolving hard phlegm/ mucus plugs – Side effect: Rhinorrhoea, lacrymation, gastric irritation, hypersensitivity. • Acetylcysteine: – Derivatives of cysteine – Reduce/ open the disulfide bridges in mucoproteins present in sputum. – These drugs also act as antioxidants and may therefore reduce airway inflammation. – Side effects: Not popular one
  8. 8. Antitussives • Opioids (Codeine/ pholcodeine): • Codeine: – An opium alkaloid; less potent than morphine. – Codeine, hydrocodone and hydromorphone are decrease sensitivity of central cough center to peripheral stimuli and decrease mucosal secretions. – Suppresses cough center (for 6 h). – The antitussive action is blocked by naloxone. – Abuse liability is low, but present; constipation is the chief drawnback. – Higher doses respiratory depression and drowsiness can occur- driving may be impaired. – Dose: adult 10-30 mg frequently used as syrup codeine phos. 4-8 ml. • Pholcodeine: – Similar in efficacy as antitussive to codeine. – Long acting codeine (12 h); Dose: 10-15 g • Ethylmorphine: – Similar to codeine; Dose: 10-15 mg.
  9. 9. Antitussives • Nonopioids: • Noscapine (Narcotine): – Opium alkaloid of benzoisoquinoline . – It depresses cough but not narcotic, analgesic or dependence including properties. – Equipotent antitussive as codeine and useful in spasmodic cough. – Side effect: Headache, nausea. It can produce bronchoconstriction by stimulating histamine release. • Dextromethorphan: – Synthetic compound; d-isomer has selective antitussive action; l-isomer has analgesic property. – Effective as codeine, doesn't depress the mucociliary function of airway mucosa. – Antitussive effect is not blocked by naloxone – Side effect: Dizziness, nausea, drowsiness, ataxia. – Dose: 10-20 mg adult • Oxeladin: Syn. centrally acting antitussive agent
  10. 10. Bronchodilators • Bronchospasm and can induce or aggravate cough. Pulmonary receptor stimulation can indcue both cough and bronchoconstriction. • Bronchodilators relieve cough and clear secretions by increasing surface velocity of airflow during cough.
  11. 11. Antihistamines • H1 receptor antagonist have little effect on rhinitis associated with colds. • Antihistamines reduce the parasympathetic tone of arterioles and decrease secretion through their anticholinergic activity. • Chlorpheniramine (2-5 mg), diphenhydramine (15-20 mg) and promethazine (15-20 mg) are commonly used as a antitussives. • Second generation antihistamines like terfenadine, loratadine are ineffective.

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