Antitussive Drugs
Antitussive drugs are medications used to suppress or alleviate coughing. They act centrally on the brainstem to reduce the cough reflex and are typically used for nonproductive coughs that are irritating or interfering with rest.
Classification
- 1. Opioids: Codeine, Ethylmorphine, Hydrocodone
- 2. Non-opioids: Dextromethorphan, Noscapine
(Opioid antitussives are generally stronger but carry a higher risk of side effects and dependence. Non-opioids are safer and widely available over the counter in many countries.)
Pharmacodynamics
- Opioids such as codeine and hydrocodone act centrally on the cough center in the medulla. They bind to mu-opioid receptors, leading to suppression of the cough reflex and often produce mild sedation.
- Non-opioids, like dextromethorphan and noscapine, also act centrally but do not bind to opioid receptors.
- Dextromethorphan inhibits NMDA receptors and modulates serotoninergic and sigma-1 receptors, reducing the cough reflex.
- Noscapine acts by binding to sigma receptors and modulating central pathways without causing opioid-like effects.
Side Effects
- Opioids (Codeine, Ethylmorphine, Hydrocodone):
- Common: Constipation, nausea, drowsiness, respiratory depression
- Rare: Addiction, hallucinations, hypotension, bradycardia
- Non-opioids (Dextromethorphan, Noscapine):
- Common: Dizziness, drowsiness, nausea, GI disturbances
- Rare: Serotonin syndrome, allergic reactions, CNS depression, hallucinations (high doses of dextromethorphan)