Antitussives

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Chapter: Essential pharmacology : Drugs for Cough and Bronchial Asthma

These are drugs that act in the CNS to raise the threshold of cough centre or act peripherally in the respiratory tract to reduce tussal impulses, or both these actions.


ANTITUSSIVES

 


These are drugs that act in the CNS to raise the threshold of cough centre or act peripherally in the respiratory tract to reduce tussal impulses, or both these actions. Because they aim to control rather than eliminate cough, antitussives should be used only for dry unproductive cough or if cough is unduly tiring, disturbs sleep or is hazardous (hernia, piles, cardiac disease, ocular surgery).

 

 

Opioids

 

Codeine (see Ch. No. 34) An opium alkaloid, qualitatively similar to but less potent than morphine. It is more selective for cough centre and is treated as the standard antitussive; suppresses cough for about 6 hours. The antitussive action is blocked by naloxone indicating that it is exerted through opioid receptors in the brain. Abuse liability is low, but present; constipation is the chief draw back. At higher doses respiratory depression and drowsiness can occur—driving may be impaired. Like morphine, it is contraindicated in asthmatics and in patients with diminished respiratory reserve.

 

Dose: 10–30 mg; children 2–6 years 2.5–5 mg, 6–12 years 5–10 mg, frequently used as syrup codeine phos. 4–8 ml.

 

CODINE 15 mg tab, 15 mg/5 ml linctus.

 

Pholcodeine It has practically no analgesic or addicting property, but is similar in efficacy as antitussive to codeine and is longer acting—acts for 12 hours; dose: 10–15 mg. (ETHNINE 5 mg/5 ml syr).

 

Non-Opioids

 

Noscapine (Narcotine) An opium alkaloid of the benzoisoquinoline series (see Ch. No. 34). It depresses cough but has no narcotic, analgesic or dependence inducing properties. It is nearly equipotent antitussive as codeine, especially useful in spasmodic cough. Headache and nausea occur occasionally as side effect. It can release histamine and produce bronchoconstriction in asthmatics.

 

Dose: 15–30 mg, children 2–6 years 7.5 mg, 6–12 years 15 mg.

 

COSCOPIN 7 mg/5 ml syrup, COSCOTABS 25 mg tab.

 

Dextromethorphan A synthetic compound; the disomer has selective antitussive action (raises threshold of cough centre) while lisomer is analgesic. Dextromethorphan is as effective as codeine, does not depress mucociliary function of the airway mucosa and is practically devoid of constipating and addicting actions. The antitussive action lasts for ~ 6 hours and is not blocked by naloxone: therefore not exerted through opioid receptors.

 

Side effect: Dizziness, nausea, drowsiness, ataxia.

 

Dose: 10–20 mg, children 2–6 years 2.5–5 mg, 6–12 years 5–10 mg.

 

Chlophedianol It is a centrally acting antitussive with slow onset and longer duration of action. Side effect: Dryness of mouth, vertigo, irritability.

Dose: 20–40 mg; DETIGON, TUSSIGON 20 mg/5 ml linctus with Ammon. chloride 50 mg and menthol 0.25 mg.

 


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