Antiemetic

An antiemetic is a medication that prevents or treats nausea and vomiting. They are used for a range of causes, including postoperative nausea and vomiting (PONV), chemotherapy-induced nausea and vomiting (CINV), motion sickness, gastroenteritis, and migraine-associated nausea.

Most antiemetics act by blocking neurotransmitter signaling involved in the vomiting reflex. The major classes include serotonin 5-HT3 receptor antagonists (ondansetron, granisetron, palonosetron); dopamine D2 receptor antagonists (metoclopramide, prochlorperazine); neurokinin-1 (NK1) receptor antagonists (aprepitant, fosaprepitant); anticholinergics (scopolamine); corticosteroids (dexamethasone); and benzodiazepines (lorazepam) used as adjuncts for anxiety-related or anticipatory symptoms.

Serotonin 5-HT3 receptor antagonists are effective for CINV and PONV but can cause headache, constipation, and, in some cases, QT interval prolongation. Dopamine antagonists provide antiemetic and prokinetic effects; their use can be limited by extrapyramidal symptoms, sedation, and, rarely, tardive dyskinesia. NK1 receptor antagonists add efficacy, particularly for delayed CINV, with possible fatigue, hiccups, and drug interactions via CYP3A4. Scopolamine patches are useful for motion sickness and prolonged nausea prevention but may cause dry mouth, blurred vision, and confusion, especially in older adults. Dexamethasone is a widely used antiemetic, often in combination regimens for CINV or PONV, with potential hyperglycemia and mood changes on longer courses. Lorazepam may help with anticipatory nausea and anxiety.

Therapy is tailored to the cause, patient risk factors, and potential drug interactions, and is guided by clinical guidelines that favor combination regimens for high-risk situations.