Introduction
Antitussives are medicines that suppress the frequency and intensity of coughing without interfering with normal mucus clearance. They are mainly used for dry, irritating and non-productive cough. These drugs act either on the cough centre in the brain or directly on respiratory receptors.
Classification of Antitussives
- Centrally acting antitussives
- Centrally as well as peripherally acting antitussives
- Peripherally acting antitussives
- Miscellaneous agents
(A) Centrally Acting Antitussives
These medicines suppress cough by acting on the cough centre in the medulla. They include opioid and non-opioid drugs.
1. Opioid Derivatives
Codeine
A semi-synthetic opioid with strong cough-suppressing action. It is effective in low doses and causes less constipation and addiction compared to morphine.
Dose: 10 mg BD or TDS
Adverse effects: constipation, mild drowsiness; overdose may cause respiratory depression, convulsions, postural hypotension and tachycardia.
Pholcodeine
Structurally related to codeine. More potent, longer-acting and better tolerated. Causes less constipation and drowsiness, making it suitable for long-term use.
Dose: 10–15 mg BD
Noscapine
A natural opium alkaloid with good antitussive action but no analgesic or addictive properties. Minimal constipation.
Dose: 15 mg TDS
High doses may cause: nausea, headache, tremors
Morphine
Powerful cough suppressant but avoided due to high addiction potential. Reserved for terminal illness-associated cough.
2. Non-Opioid Centrally Acting Antitussives
Dextromethorphan
A widely used antitussive with minimal drowsiness, no analgesia and extremely low addiction liability.
Dose: 10 mg TDS
Pipazethate
A synthetic phenothiazine derivative with antitussive action and negligible CNS depression.
Dose: 40 mg TDS
Common Preparation
- Codeine phosphate: 15 mg/5 ml Codeine linctus
(B) Centrally as well as Peripherally Acting Antitussives
Benzonatate
Structurally similar to the local anaesthetic tetracaine. Acts by:
- Depressing cough centre (central action)
- Inhibiting pulmonary stretch receptors (peripheral action)
- Providing mild local anaesthetic effect
Dose: 100–200 mg TDS
Side effects: drowsiness, nausea, headache, vertigo (high doses)
(C) Peripherally Acting Antitussives
Prenoxdiazine
Acts mainly by inhibiting pulmonary stretch receptors and relieving broncho-spasm. Moderate cough-suppressing effect.
Dose: 100–200 mg TDS
Topical Local Anaesthetics
Lidocaine or Bupivacaine may be applied to pharynx or larynx to reduce sensitivity of cough receptors. Commonly used during bronchoscopy or when other treatments fail.
(D) Miscellaneous Agents
Demulcents
These coat and soothe the pharyngeal mucosa, reducing irritation. Useful in dry, irritating cough.
- Honey
- Liquorice
- Syrup Tolu
- Syrup Vasaka
Important Note
Antitussives should not be used in cough associated with:
- Asthma
- Chronic bronchitis
- Bronchiectasis
They may cause harmful retention and thickening of sputum in these conditions.
Preparations
- Prenoxdiazine tablets: 100 mg, 200 mg (Prenoxid)
- Lidocaine (Lignocaine): 2% jelly, 2% viscous, 2%–4% solution, 10% and 15% spray (Gesicaine, Xylocaine)
Detailed Notes:
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