Nausea and vomiting arise from multiple physiological triggers — the vomiting centre in the brain and the chemoreceptor trigger zone (CTZ) in the area postrema can be activated by motion, chemicals, medications, GI irritation, and the central nervous system. Antiemetics work by blocking the receptors responsible for triggering the emetic reflex. Different antiemetic classes target different receptor pathways:
- 5-HT3 antagonists (ondansetron/Zofran) — most effective for chemotherapy-induced and post-operative nausea; block serotonin receptors in the GI tract and CTZ
- Dopamine D2 antagonists (prochlorperazine/Compazine, metoclopramide/Reglan) — block dopamine in the CTZ; useful for nausea from various causes; risk of extrapyramidal side effects
- Phenothiazine antihistamines (promethazine/Phenergan) — combined H1 and dopamine blockade; useful for motion sickness and general nausea; sedating
- Classic antihistamines (dimenhydrinate/Dramamine) — OTC; H1 blocker for motion sickness and mild nausea; sedating
Nausea Medications Available at Lucas Clinic
- Compazine (Prochlorperazine) — 5/10 mg Rx tablets; dopamine antagonist phenothiazine for severe nausea
- Dramamine (Dimenhydrinate) — 50 mg OTC; antihistamine for motion sickness
- Promethazine (Phenergan) — 12.5–50 mg Rx; phenothiazine antihistamine for nausea and pre-op sedation
- Reglan (Metoclopramide) — 5/10 mg Rx; prokinetic dopamine antagonist for GERD and gastroparesis
- Zofran (Ondansetron) — 4/8 mg Rx ODT and tablets; 5-HT3 antagonist for chemo and post-op nausea