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Antiemetic Drugs: Classification, Mechanism, Therapeutic Uses, and Adverse Effects
Classification of Antiemetic Drugs
- 5-HT3 (Serotonin) Antagonists: Ondansetron, Granisetron
- Dopamine (D2) Antagonists: Metoclopramide, Domperidone, Prochlorperazine
- Antihistamines (H1 Antagonists): Dimenhydrinate, Meclizine, Promethazine
- Anticholinergics (Muscarinic Antagonists): Scopolamine
- NK1 (Neurokinin-1) Receptor Antagonists: Aprepitant
- Cannabinoids: Dronabinol, Nabilone
- Benzodiazepines: Lorazepam
Mechanism of Action of Antiemetic Drugs
- 5-HT3 Antagonists: Block serotonin receptors in the GI tract and chemoreceptor trigger zone (CTZ), reducing nausea and vomiting signals.
- Dopamine (D2) Antagonists: Block dopamine receptors in the CTZ, preventing emetic signals from reaching the vomiting center.
- Antihistamines (H1 Antagonists): Block histamine receptors in the vestibular system and CTZ, effective for motion sickness.
- Anticholinergics (Muscarinic Antagonists): Inhibit muscarinic receptors in the vestibular system, reducing motion-induced nausea.
- NK1 Receptor Antagonists: Block neurokinin-1 receptors, preventing substance P from activating the vomiting reflex.
- Cannabinoids: Activate cannabinoid receptors, reducing nausea signals within the central nervous system.
- Benzodiazepines: Enhance GABA action, reducing anxiety and chemotherapy-related nausea.
Therapeutic Uses of Antiemetic Drugs
- 5-HT3 Antagonists: Used in chemotherapy-induced nausea, postoperative nausea, and radiation therapy-induced nausea.
- Dopamine (D2) Antagonists: Effective for GI-related nausea, chemotherapy, and migraine.
- Antihistamines (H1 Antagonists): Primarily for motion sickness, vertigo, and mild pregnancy-related nausea.
- Anticholinergics (Muscarinic Antagonists): Effective in preventing motion sickness.
- NK1 Receptor Antagonists: Used with 5-HT3 antagonists and corticosteroids in chemotherapy-induced nausea.
- Cannabinoids: For refractory chemotherapy-induced nausea and appetite stimulation.
- Benzodiazepines: For anticipatory nausea in chemotherapy and as adjunctive therapy.
Adverse Effects of Antiemetic Drugs
- 5-HT3 Antagonists: Headache, constipation, QT interval prolongation.
- Dopamine (D2) Antagonists: Extrapyramidal symptoms, sedation, hypotension.
- Antihistamines (H1 Antagonists): Sedation, dry mouth, dizziness, urinary retention.
- Anticholinergics (Muscarinic Antagonists): Dry mouth, blurred vision, urinary retention, drowsiness.
- NK1 Receptor Antagonists: Fatigue, diarrhea, hiccups.
- Cannabinoids: Euphoria, dizziness, dysphoria, tachycardia.
- Benzodiazepines: Sedation, dependency, cognitive impairment.
