Anti-emetics

Anti-emetics

Anti-emetics are a class of drugs used to prevent or alleviate nausea and vomiting, which are symptoms that can arise from a variety of causes including motion sickness, chemotherapy, surgery, and gastroenteritis. These medications work through different mechanisms to target the pathways involved in the vomiting reflex.

Mechanism of Action

The vomiting reflex is a complex process involving the central nervous system, the gastrointestinal tract, and the vestibular system. Anti-emetics can act on different receptors and pathways to inhibit this reflex:

• 5-HT3 Receptor Antagonists: These drugs, such as Ondansetron, block serotonin receptors in the central nervous system and gastrointestinal tract. They are particularly effective in treating nausea and vomiting induced by chemotherapy and postoperative conditions.

• Dopamine Antagonists: Medications like Metoclopramide and Prochlorperazine block dopamine receptors in the brain, which can help control nausea and vomiting associated with migraines and gastrointestinal disorders.

• Antihistamines: Drugs such as Diphenhydramine and Meclizine are effective in treating motion sickness by blocking histamine receptors in the vestibular system.

• Anticholinergics: Scopolamine is an example of an anticholinergic that prevents motion sickness by blocking acetylcholine receptors in the vestibular system.

• NK1 Receptor Antagonists: Aprepitant is used to prevent chemotherapy-induced nausea and vomiting by blocking neurokinin-1 receptors in the brain.

Clinical Uses

Anti-emetics are used in various clinical settings:

• Chemotherapy-Induced Nausea and Vomiting (CINV): 5-HT3 receptor antagonists, NK1 receptor antagonists, and corticosteroids are commonly used in combination to prevent CINV.

• Postoperative Nausea and Vomiting (PONV): 5-HT3 receptor antagonists and dopamine antagonists are often used to manage PONV.

• Motion Sickness: Antihistamines and anticholinergics are effective in preventing and treating motion sickness.

• Gastroenteritis: Dopamine antagonists can be used to alleviate symptoms of nausea and vomiting in gastroenteritis.

Side Effects

The side effects of anti-emetics vary depending on the class of drug:

• 5-HT3 Receptor Antagonists: Common side effects include headache, constipation, and dizziness.

• Dopamine Antagonists: These can cause extrapyramidal symptoms, sedation, and hypotension.

• Antihistamines: Sedation, dry mouth, and blurred vision are common side effects.

• Anticholinergics: Dry mouth, urinary retention, and blurred vision can occur.

• NK1 Receptor Antagonists: Fatigue and hiccups are potential side effects.

Also see

• Nausea
• Vomiting
• Chemotherapy
• Motion Sickness
• Gastroenteritis