What dose of Zofran (ondansetron) and Pepcid (famotidine) is recommended for managing nausea and vomiting?

Recommended Dosing for Ondansetron (Zofran) and Famotidine (Pepcid) in Nausea Management

For nausea and vomiting management, ondansetron should be dosed at 4-8 mg IV/PO every 8 hours as a second-line agent after dopamine antagonists, while famotidine is not recommended as an antiemetic and should not be used for this indication. 1

Ondansetron Dosing Strategy

Position in Treatment Algorithm

• Ondansetron is a second-line agent, not first-line therapy 1
• The American College of Emergency Physicians recommends dopamine receptor antagonists (haloperidol 0.5-2 mg IV/PO every 6-8 hours, metoclopramide 10-20 mg PO/IV 3-4 times daily, or prochlorperazine 5-10 mg PO/IV 3-4 times daily) as first-line treatment 1
• Add ondansetron only when first-line dopamine antagonists are insufficient 1

Standard Ondansetron Dosing

• 4-8 mg IV/PO every 8 hours for general nausea management 1
• For breakthrough nausea, start with as-needed (PRN) dosing 1
• If nausea persists, switch to scheduled around-the-clock administration for at least one week 1, 2
• The 8 mg dose can be given orally twice daily for persistent nausea 1

Context-Specific Dosing

For Chemotherapy-Induced Nausea:

• Grade 3 emetogenic chemotherapy: 16 mg orally pretreatment, with option for 4 mg orally twice daily for 2 days 3
• Grade 4 emetogenic chemotherapy: Use granisetron 1 mg orally pretreatment instead, as it is preferred over ondansetron in this setting 3
• Continue for 2-3 days post-chemotherapy, not longer 2

For Postoperative Nausea:

• 4 mg IV preoperatively has demonstrated efficacy 4, 5
• This single preoperative dose reduces postoperative nausea from 47% to 7% and shortens hospital stay by 18 hours 5

Famotidine (Pepcid) for Nausea

Famotidine is NOT an antiemetic and should not be used for nausea management. Famotidine is an H2-receptor antagonist used for acid suppression, not nausea control. None of the clinical guidelines or evidence supports its use as an antiemetic agent.

Critical Implementation Points

Multimodal Approach Required

• Never use ondansetron as monotherapy 3
• Combine with dexamethasone 4-8 mg PO/IV daily for enhanced efficacy 3, 6
• For persistent nausea despite ondansetron, add prochlorperazine 10 mg PO every 6 hours or haloperidol 0.5-1 mg PO every 6-8 hours 6
• Use medications with different mechanisms of action rather than increasing ondansetron dose 1

Common Pitfalls to Avoid

• Ondansetron causes constipation, which can worsen nausea 1
• Always address constipation proactively when using ondansetron 1
• Do not prescribe multiple days of ondansetron for acute gastroenteritis, as it may increase stool volume 2
• In pediatric gastroenteritis, use only a single dose in children >4 years; do not prescribe to children <4 years 2

When to Escalate Therapy

• If nausea persists despite scheduled ondansetron plus one dopamine antagonist, add dexamethasone 4-8 mg daily 6
• Consider lorazepam 1 mg PO every 1-2 hours for anticipatory or anxiety-associated nausea 6
• Always reassess for underlying causes (constipation, CNS pathology, electrolyte abnormalities) before adding more antiemetics 6

Cost Considerations

• Ondansetron costs approximately $17 per 4 mg IV dose compared to $2.50 for dimenhydrinate 50 mg IV, with equivalent efficacy in postoperative settings 4
• Reserve ondansetron for situations where dopamine antagonists have failed or are contraindicated 1