Table 2.
Antiemetics
| Drugs | Mechanism of Action | Special Considerations |
|---|---|---|
| Prochlorperazine, promethazine, chlorpromazine | Phenothiazines: predominantly D2-dopamine antagonism, also M1-muscarinic and H1-histamine antagonism | High incidence of extrapyramidal reactions, may cause hypotension, promethazine black box warning for children <2 y |
| Metoclopramide, domperidone | Benzamides: D2-dopamine antagonism, weak 5-HT3 antagonism at higher doses, enhances acetylcholine at neuromuscular junction | Prokinetic properties, domperidone does not cross blood-brain barrier, metoclopramide pregnancy category B |
| Droperidol, haloperidol | Butyrophenones: D2-dopamine and α antagonism | Second-line agents, droperidol black box warning due to QT prolongation and torsades |
| Diphenhydramine, dimenhydrinate, cyclizine | H1-histamine antagonism | Primarily used for motion sickness, sedating |
| Ondansetron, granisetron, dolasetron, palonosetron | Selective 5-HT3 antagonism | Favorable toxicity profile, high cost |
| Aprepitant, fosaprepitant | Selective NK1-substance P antagonism | Used for chemotherapy, synergistic effect with serotonin receptor antagonists and corticosteroids |
| Dexamethasone, methylprednisolone | Corticosteroid: inhibits inflammatory cytokines, produces glucocorticoid and mineralocorticoid effects | Prophylaxis for chemotherapy-induced vomiting |
| Lorazepam, alprazolam | Binds to benzodiazepine receptors, enhances GABA effects | Sedating, often used as adjunctive agent |
| Dronabinol, nabilone | Cannabinoids: exact mechanism unknown, possible interaction with vomiting control center | Multiple other effects, most studied in cancer patients |
Abbreviations: 5-HT3, 5-hydroxytryptamine-3; GABA, γ-aminobutyric acid.