Antiemetic Drugs
Antiemetic drugs are medications used to prevent or treat nausea and vomiting, which are often caused by factors such as chemotherapy, motion sickness, or gastrointestinal disorders. These drugs work by acting on specific receptors and neurotransmitter systems involved in the vomiting reflex.
Classification
- Dopamine D2 receptor antagonists: Metoclopramide, Domperidone
- Serotonin 5HT3 receptor antagonists: Ondansetron, Granisetron
- Anticholinergic agents: Scopolamine
- Histamine H1 receptor antagonists: Promethazine, Diphenhydramine
- Others: Fosaprepitant, Dexamethasone
Pharmacodynamics
- Dopamine D2 receptor antagonists (e.g. Metoclopramide, Domperidone) block dopamine receptors in the chemoreceptor trigger zone (CTZ) and gastrointestinal tract, thereby reducing nausea and vomiting.
- Serotonin 5HT3 receptor antagonists (e.g. Ondansetron, Granisetron) inhibit serotonin at 5HT3 receptors in both the gastrointestinal tract and central nervous system, preventing the activation of the vomiting reflex.
- Scopolamine blocks the action of acetylcholine in the vestibular system, helping to alleviate motion sickness and associated nausea and vomiting.
- Histamine H1 receptor antagonists (e.g. Promethazine, Diphenhydramine) act by blocking histamine receptors in the inner ear and brain, reducing motion sickness and nausea.
- Fosaprepitant is a neurokinin-1 (NK1) receptor antagonist used for chemotherapy-induced nausea and vomiting (CINV). Dexamethasone is a corticosteroid that also has anti-inflammatory effects, often used in combination with other antiemetics to prevent nausea in chemotherapy patients.