What is the treatment for a patient with vomiting and diarrhea suspected to have food poisoning?

Treatment for Suspected Food Poisoning with Vomiting and Diarrhea

For an adult patient with suspected food poisoning presenting with vomiting and diarrhea, begin immediate oral rehydration therapy (ORS) as first-line treatment, avoid antimicrobials unless specific high-risk features are present, and consider ondansetron to facilitate oral intake if vomiting is severe. 1, 2

Initial Assessment and Hydration Status

Assess the patient's hydration level immediately to determine treatment intensity:

• Mild dehydration (3-5% fluid deficit): Start with 50 mL/kg of ORS over 2-4 hours 1
• Moderate dehydration (6-9% fluid deficit): Administer 100 mL/kg of ORS over 2-4 hours 1
• Severe dehydration (≥10% deficit, shock, altered mental status): This is a medical emergency requiring immediate IV fluids with isotonic solutions (Ringer's lactate or normal saline) until pulse, perfusion, and mental status normalize 1, 2

Rehydration Strategy

Oral rehydration solution is the cornerstone of treatment for food poisoning with vomiting and diarrhea 1, 2:

• If vomiting is present: Start with small, frequent volumes (5-10 mL every 1-2 minutes) using a teaspoon, syringe, or medicine dropper, then gradually increase as tolerated 1, 3
• Use reduced osmolarity ORS containing 50-90 mEq/L of sodium for rehydration 1, 2
• Replace ongoing losses: Administer 10 mL/kg for each watery stool and 2 mL/kg for each vomiting episode 1, 2

Managing Vomiting

Ondansetron can be considered to facilitate oral rehydration in adults with significant vomiting 1, 3:

• Typical adult dose is 4-8 mg orally 4
• Important caveat: Avoid ondansetron in patients with congenital long QT syndrome, and use with caution in those with electrolyte abnormalities (hypokalemia, hypomagnesemia), congestive heart failure, or bradyarrhythmias due to risk of QT prolongation 4
• Monitor for serotonin syndrome if patient is on SSRIs, SNRIs, or other serotonergic medications 4

Antimicrobial Therapy Decision

Do NOT give empiric antibiotics for typical food poisoning with watery diarrhea 1, 2:

Exceptions requiring antimicrobial consideration include:

• Bloody diarrhea with fever suggesting shigellosis 1, 2
• Recent international travel with fever ≥38.5°C or signs of sepsis 2
• Immunocompromised status 2
• Signs of systemic illness or sepsis 1

Critical pitfall: Never use antimicrobials if Shiga toxin-producing E. coli (STEC) is suspected, as this increases risk of hemolytic uremic syndrome 2

Antimotility Agents

Loperamide may be offered to immunocompetent adults with acute watery diarrhea once adequately hydrated 1, 3:

Absolute contraindications for loperamide:

• Any patient with bloody diarrhea 1
• Fever present 1
• Suspected inflammatory diarrhea 1, 2
• Risk of toxic megacolon 1

Dietary Management

Resume normal, age-appropriate diet immediately after rehydration 1, 2, 3:

• Do not withhold food during the illness 2, 3
• Early refeeding improves outcomes and does not worsen symptoms 3
• Avoid the outdated practice of prolonged dietary restriction 2

Adjunctive Therapies

Probiotics may be offered to reduce symptom severity and duration in immunocompetent adults 1, 2

Monitoring and Reassessment

Reassess hydration status after 2-4 hours of ORS therapy 1:

• If rehydrated: Transition to maintenance therapy with continued ORS for ongoing losses 1, 2
• If still dehydrated: Re-estimate fluid deficit and restart rehydration phase 1
• If unable to tolerate oral intake despite antiemetics: Consider nasogastric ORS administration or IV fluids 1, 2

Common Pitfalls to Avoid

• Prescribing antimotility agents when fever or bloody diarrhea is present - this can lead to toxic megacolon and serious complications 1, 2
• Routine use of antibiotics for watery diarrhea - this is unnecessary and promotes resistance 1, 2
• Withholding food during illness - early refeeding is beneficial 2, 3
• Inadequate fluid replacement - ongoing losses must be continuously replaced throughout the illness 1
• Using ondansetron without checking for QT-prolonging medications or electrolyte abnormalities - this can precipitate dangerous arrhythmias 4

When to Seek Further Evaluation

Advise the patient to return if:

• Unable to tolerate any oral fluids despite antiemetics 3
• Development of bloody diarrhea 3
• High fever develops or worsens 3
• Signs of worsening dehydration (decreased urine output, dizziness, confusion) 1
• Symptoms persist beyond 3-5 days 1