Chapter 52: Antiemetic and Antinausea Drugs

The vomiting center located in the medulla and the chemoreceptor trigger zone in the brain stem receive signals from multiple neurotransmitter systems including acetylcholine, dopamine, histamine, serotonin, and substance P, and these pathways form the basis for drug selection and mechanism of action. Seven major drug classes target these pathways through different mechanisms: anticholinergic agents like scopolamine block acetylcholine signaling in the vestibular system to prevent motion sickness; antihistamines including meclizine and diphenhydramine suppress vestibular and reticular system activity; antidopaminergic medications such as prochlorperazine and promethazine block dopamine in the chemoreceptor trigger zone but carry risks of extrapyramidal side effects and sedation; neurokinin receptor antagonists including aprepitant block substance P pathways and are standard components of chemotherapy-induced nausea and vomiting prevention regimens; prokinetic agents like metoclopramide enhance gastric motility while blocking dopamine; serotonin antagonists including ondansetron and palonosetron revolutionized cancer and surgical nausea management by blocking 5-HT3 receptors; and tetrahydrocannabinoid derivatives modify signals in the reticular formation while stimulating appetite in immunocompromised patients. The chapter addresses specific clinical scenarios including motion sickness, vertigo, delayed gastric emptying, chemotherapy-induced emesis, and postoperative nausea, while detailing contraindications such as angle-closure glaucoma, seizure disorders, and pregnancy concerns. Nursing responsibilities encompass baseline assessment, hydration and electrolyte monitoring, patient education regarding administration routes, prevention of medication errors, and counseling on lifestyle modifications. Drug interactions with central nervous system depressants, alcohol, and various medications are examined, alongside discussion of herbal approaches such as ginger supplementation and their bleeding risk considerations.