What is the best course of treatment for a patient presenting with a 3-day history of nausea, vomiting, and diarrhea, unable to keep anything down, experiencing generalized body aches, and requesting IV fluid rehydration and a refill of Phenergan (promethazine), with symptoms consistent with viral gastroenteritis?

Treatment of Viral Gastroenteritis with Nausea, Vomiting, and Dehydration

For this patient with 3-day viral gastroenteritis unable to tolerate oral intake, provide IV fluid rehydration and prescribe ondansetron (not promethazine) as the antiemetic, as ondansetron is significantly more effective at facilitating oral rehydration and reducing the need for hospitalization. 1

Immediate Management: IV Fluid Rehydration

• Administer IV fluid rehydration for this patient who cannot maintain oral intake after 3 days and is experiencing dehydration symptoms (generalized body aches, inability to keep anything down). 2
• The patient's inability to tolerate oral rehydration therapy after 3 days, combined with persistent vomiting and dry heaves, meets criteria for IV fluid administration. 2
• Once vomiting is controlled with antiemetics, transition back to oral rehydration solutions to complete rehydration. 3

Antiemetic Selection: Ondansetron Over Promethazine

The patient's request for promethazine should be declined in favor of ondansetron, which has superior efficacy and safety profile for gastroenteritis-related vomiting.

Why Ondansetron is Preferred:

• Ondansetron reduces vomiting episodes significantly more than placebo (median 0 episodes vs 0-7 episodes, P=.001) and decreases IV fluid requirements (P=.015) and hospital admissions (P=.007). 1
• A single oral dose of ondansetron facilitates oral rehydration therapy without significant adverse events. 4
• Ondansetron is considered first-line antiemetic therapy and increases success of oral rehydration while minimizing need for IV therapy and hospitalization. 4, 3

Why Promethazine Should Be Avoided:

• Promethazine is significantly less effective than alternative antiemetics like prochlorperazine, with 31% treatment failure rate versus 9.5% (P=.03), and causes more sedation (71% versus 38%, P=.002). 5
• The FDA label warns that promethazine may cause respiratory depression, has lower seizure threshold risks, and should be used at the lowest effective dose. 6
• Promethazine causes excessive drowsiness which interferes with oral rehydration efforts. 5

Ondansetron Dosing:

• Administer ondansetron 4-8 mg orally or IV initially, then prescribe 4-8 mg every 8 hours as needed for up to 48 hours. 1
• Monitor for the expected side effect of increased diarrhea frequency, which occurred more in the ondansetron group but did not affect overall outcomes. 1

Diagnostic Considerations

Rule out bacterial pathogens and C. difficile before attributing symptoms solely to viral gastroenteritis:

• Order stool testing for bacterial pathogens (Salmonella, Campylobacter, Shigella) and C. difficile toxin, particularly given the workplace outbreak and 3-day symptom duration. 2, 7
• The absence of fever and bloody diarrhea makes bacterial infection less likely but does not exclude it. 7
• Multiplex PCR testing offers higher sensitivity (94% for norovirus) and faster results than traditional stool cultures. 7

Expected Clinical Course

Viral gastroenteritis typically resolves within 2-3 days for norovirus, but symptoms can persist up to 7 days:

• Norovirus causes vomiting and nonbloody diarrhea lasting 2-3 days in healthy adults, though it can extend to 4-6 days in certain populations. 8
• If symptoms persist beyond 7 days, consider alternative diagnoses including post-infectious enteropathy, parasitic infections (Giardia), or C. difficile. 8, 7
• The green bilious vomitus is consistent with prolonged vomiting and does not indicate surgical pathology in this context. 2

Monitoring and Follow-Up

• Monitor QTc interval if using ondansetron, especially if the patient has cardiac risk factors or is taking other QT-prolonging medications. 2
• Reassess hydration status after IV fluid administration and antiemetic therapy to determine readiness for discharge. 2
• Instruct the patient to return immediately if she develops high fever, bloody stools, severe abdominal pain, or signs of severe dehydration (altered mental status, inability to urinate). 8
• If symptoms persist beyond 7 days despite treatment, expand diagnostic workup to include parasitic testing and consider non-infectious causes. 8, 7

Infection Control

• Advise the patient to self-quarantine and minimize exposure to household contacts, as viral gastroenteritis is highly contagious. 2
• Emphasize proper hand hygiene to prevent fecal-oral transmission. 3
• The patient should not return to work until at least 48 hours after symptom resolution to prevent workplace transmission. 2