Antitussives
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Pholcodine
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Centrally acting opioid derivative; directly suppresses medullary cough centre
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Dizziness, sedation, nausea
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Opioid dependence, potential abuse, serotonin syndrome, lethargy, stupor, aspiration
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Dextromethorphan
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Narcotic analogue; directly suppresses medullary cough centre
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Antihistamines
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Diphenhydramine Brompheniramine Chlorpheniramine
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Histamine H1-receptor antagonists; prevent histamine-induced reactions in cells of the respiratory tract, gastrointestinal tract and blood vessels
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Sedation, headache, dizziness, nervousness, restlessness, irritability, palpitations
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Hallucinations, seizures, central nervous system depression, cardiovascular collapse, apnoea, death, anticholinergic effects
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Decongestants
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Pseudoephedrine Phenylephrine
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Sympathomimetic drugs, adrenergic receptor agonists; produce vasoconstriction within the respiratory tract mucosa, and cause increased heart rate and cardiac contractility
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Nervousness, restlessness, insomnia, trembling, headache, anxiety
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Tachycardia, palpitations, dysrhythmias, hypertension, hallucinations, agitation, central nervous system depression, seizures
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Expectorants
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Guaifenesin Ipecacuanha
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Expectorants; promote the expulsion of mucus and other materials from the respiratory tract
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Drowsiness, dizziness, headache, rash these rarely occur at therapeutic doses
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Nausea/vomiting, abdominal pain, nephrolithiasis
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Mucolytics
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Bromhexine
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Oral mucolytics; loosen and thin bronchial secretions by reducing surface tension and viscosity of mucus
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Dizziness, headache, rash these rarely occur at therapeutic doses
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Nausea/vomiting, abdominal pain, diarrhoea
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