How to Order Ondansetron, Metoclopramide, and Dimenhydrinate
Drug | Condition | Route | Dose |
Ondansetron | Chemotherapy-Induced Nausea and Vomiting (CINV) | IV | 8 mg over 15 minutes, 30 minutes before chemotherapy. Subsequent doses at 4 and 8 hours after the first dose. |
Oral | 8 mg 30 minutes before chemotherapy, then 8 mg 8 hours later, followed by 8 mg twice daily for 1-2 days post-chemotherapy. | ||
Postoperative Nausea and Vomiting (PONV) | IV | 4 mg single dose over 2-5 minutes before anesthesia or at the end of surgery. | |
Oral | 16 mg 1 hour before anesthesia. | ||
Plasil (Metoclopramide) | Gastroparesis | Oral | 10-15 mg 30 minutes before meals and at bedtime. |
Chemotherapy-Induced Nausea and Vomiting (CINV) | IV | 1-2 mg/kg/dose 30 minutes before chemotherapy, repeated every 2-3 hours for up to 3 doses. | |
Postoperative Nausea and Vomiting (PONV) | IV | 10 mg single dose over 1-2 minutes. | |
Dramamine (Dimenhydrinate) | Motion Sickness | Oral | 100 mg 30 minutes to 1 hour before travel, then every 4-6 hours as needed, max 400 mg/day. |
IM/IV | 50 mg 30 minutes before travel, repeat every 4-6 hours as needed. | ||
Vertigo | Oral | 100 mg every 4-6 hours. |
Comprehensive Guide to Anti-Emetic Drugs
Antiemetic drugs are crucial in managing nausea and vomiting, which can arise from various conditions such as motion sickness, medication side effects, gastrointestinal disorders, chemotherapy, or surgery. This guide provides an in-depth overview of commonly used antiemetics: Ondansetron, Metoclopramide, and Dimenhydrinate, including their mechanisms of action, indications, and dosing.
Ondansetron
Mechanism of Action
Ondansetron is a serotonin (5-HT3) receptor antagonist. It works by blocking serotonin, a natural substance that causes nausea and vomiting, at 5-HT3 receptors in the central nervous system and the gastrointestinal tract.
Indications
Chemotherapy-Induced Nausea and Vomiting (CINV)
Postoperative Nausea and Vomiting (PONV)
Radiation Therapy-Induced Nausea and Vomiting
Dosing and Formulations
Chemotherapy-Induced Nausea and Vomiting (CINV)
Oral:
Children < 4 years:
< 0.3 m²: 1 mg three times a day
0.3-0.6 m²: 2 mg three times a day
0.6-1 m²: 3 mg three times a day
≥ 1 m²: 4 mg three times a day
Children 4-11 years: 4 mg three times a day
Children ≥ 12 years and Adults: 8 mg three times a day or 24 mg once a day
IV:
Infants ≥ 6 months and Children: 0.15 mg/kg/dose 30 minutes before chemotherapy, and again at 4 and 8 hours after the first dose, max 16 mg/dose
Adults: 0.15 mg/kg/dose 30 minutes before chemotherapy, and again at 4 and 8 hours after the first dose. Alternatively, a loading dose of 8 mg followed by an infusion of 1 mg/hour.
Postoperative Nausea and Vomiting (PONV)
Oral:
Children ≥ 2 years and < 40 kg: 0.1 mg/kg
Children ≥ 2 years and Adults: 4 mg
IV:
Children ≥ 2 years: 0.1 mg/kg
Adults: 4 mg
Formulations
Tablets: 8 mg
Injection: 8 mg/ml in 4 ml
Metoclopramide
Mechanism of Action
Metoclopramide is a dopamine (D2) receptor antagonist that works by inhibiting dopamine receptors in the chemoreceptor trigger zone (CTZ) of the brain. It enhances gastric motility and accelerates gastric emptying, which helps reduce nausea and vomiting.
Indications
Chemotherapy-Induced Nausea and Vomiting (CINV)
Postoperative Nausea and Vomiting (PONV)
Gastroparesis
Intubation of the small intestine to facilitate radiographic examination
Dosing and Formulations
Chemotherapy-Induced Nausea and Vomiting (CINV)
Oral/IV: 1-2 mg/kg/dose every 2-4 hours as needed. Use of this high dose should be accompanied by diphenhydramine to reduce the risk of extrapyramidal symptoms.
Postoperative Nausea and Vomiting (PONV)
IV: 10 mg single dose over 1-2 minutes, repeated every 6-8 hours as needed.
Gastroparesis
Oral/IM/IV: 10-15 mg 30 minutes before meals and at bedtime.
Formulations
Tablets: 10 mg
Injection: 5 mg/ml in 2 ml
Dosage Adjustments in Renal Impairment
CrCl 40-50 ml/min: 75% of the normal dose
CrCl 10-40 ml/min: 50% of the normal dose
CrCl < 10 ml/min: 25-50% of the normal dose
Dimenhydrinate
Mechanism of Action
Dimenhydrinate is an antihistamine (H1 receptor antagonist) that works by blocking H1 and muscarinic receptors in the brain, which helps prevent and treat nausea, vomiting, and dizziness associated with motion sickness and vertigo.
Indications
Motion Sickness
Vertigo
Dosing and Formulations
Motion Sickness
Oral:
Children 2-5 years: 25 mg every 6-8 hours, max 75 mg/day
Children 6-12 years: 25-50 mg every 6-8 hours, max 150 mg/day
Children ≥ 12 years and Adults: 50-100 mg every 4-6 hours, max 400 mg/day
IM/IV:
50 mg 30 minutes before travel, repeat every 4-6 hours as needed
Vertigo
Oral: 50-100 mg every 4-6 hours
Formulations
Tablets: 50 mg
Injection: 50 mg/ml (Dramamine®)
Summary
When prescribing antiemetic medications, consider the patient's age, weight, specific condition, and potential contraindications or drug interactions. Always refer to the latest clinical guidelines and institutional protocols to ensure accurate and effective patient care. Understanding and utilizing the appropriate antiemetics can significantly enhance patient comfort and treatment outcomes.
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