Chapter 59: Antiemetic Agents

Antiemetics are categorized based on their mechanism of action, working either locally to decrease GI response or centrally to block neural signals. Major centrally acting classes include the Phenothiazines, such as prochlorperazine, which depress various areas of the central nervous system (CNS) and are also indicated for the treatment of severe vomiting and intractable hiccoughs. The Nonphenothiazine agent, metoclopramide, reduces CTZ responsiveness and also treats gastroparesis. The 5-HT3 Receptor Blockers, including ondansetron and palonosetron, are crucial for controlling nausea and vomiting linked to emetogenic cancer chemotherapy, radiation therapy, and post-operative recovery. The newest class discussed is the Substance P/Neurokinin 1 (NK1) Receptor Antagonists (aprepitant, rolapitant), which selectively block CNS receptors and are highly effective, often used in combination to prevent acute and delayed chemotherapy-induced symptoms. Miscellaneous agents, such as the cannabinoids dronabinol and nabilone, are reserved for chemotherapy-related nausea unresponsive to other treatments. Important nursing considerations involve thorough assessment for contraindications like severe CNS depression or liver dysfunction, and close monitoring for adverse effects, notably sedation, dizziness, hypotension, cardiac arrhythmias, and endocrine effects. Patients taking antiemetics must be educated on safety measures, including assistance with mobility, avoiding alcohol and other CNS depressants, and the necessity of using sunscreens and protective clothing due to the risk of photosensitivity. Furthermore, the chapter highlights that parents are now advised to dispose of emetics like Ipecac Syrup, as they are no longer recommended for home poison control due to studies showing limited efficacy and increased potential toxicity.