Anti-emetic drugs aka. Anti-nausea and vomiting drugs: Ondansetron, Plasil(Metoclopramide), and Dramamine(Dimenhydrinate)

How to Order Ondansetron, Metoclopramide, and Dimenhydrinate

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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.

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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

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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

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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®)

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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.