What should be the next steps for a 42-year-old female patient with a 3-year history of chronic diarrhea, who took 119g of MiraLAX (polyethylene glycol) in 32oz of water for a capsule endoscopy prep, and is now experiencing persistent diarrhea despite only drinking water for the past 48 hours?

Management of Persistent Diarrhea Following MiraLAX Bowel Preparation

This patient is experiencing expected, self-limited diarrhea from polyethylene glycol (PEG) bowel preparation that should resolve within 24-48 hours of stopping the laxative; the primary management is supportive care with oral rehydration and monitoring for dehydration, while avoiding antidiarrheal agents that could mask underlying pathology from her chronic diarrhea.

Immediate Assessment and Monitoring

Assess for signs of dehydration and electrolyte disturbances:

• Check for decreased skin turgor, dry mucous membranes, sunken eyes, decreased urine output, tachycardia, and orthostatic symptoms (dizziness on standing) 1
• Severe dehydration (≥10% fluid deficit) manifests as altered mental status, shock, poor perfusion, and inability to tolerate oral intake 1
• The FDA label for polyethylene glycol specifically warns to stop use and seek medical attention if diarrhea develops, as this may indicate a serious condition 2

Obtain laboratory evaluation if dehydration is suspected:

• Complete blood count, comprehensive metabolic panel (particularly electrolytes, BUN, creatinine), and serum osmolality 3
• Studies of PEG bowel preparation show no clinically significant electrolyte changes in most patients, but individual monitoring is warranted given the prolonged diarrhea 4, 3, 5

Primary Management Strategy

Initiate aggressive oral rehydration:

• Administer oral rehydration solution (ORS) with reduced osmolarity (<250 mmol/L) as first-line therapy for mild-to-moderate dehydration 1
• Commercial formulations include Pedialyte, CeraLyte, or Enfalac Lytren; avoid sports drinks like Gatorade or juice due to incorrect osmolarity 1
• Adults should receive ad libitum ORS up to approximately 2 liters per day, with ongoing replacement of 120-240 mL per diarrheal stool 1

Reserve IV fluids for specific indications:

• Intravenous isotonic crystalloids (lactated Ringer's or normal saline) are indicated only for severe dehydration, shock, or failure of oral rehydration 1, 6

Critical Management Decisions

Do NOT administer loperamide or other antimotility agents at this time:

• Loperamide is contraindicated when the underlying cause of chronic diarrhea remains undiagnosed, as it may mask important diagnostic findings from the upcoming capsule endoscopy 7, 1
• Antimotility agents are specifically contraindicated in patients with fever, bloody diarrhea, or suspected inflammatory diarrhea 7, 1
• The British Society of Gastroenterology notes that while loperamide may be effective for diarrhea in IBS, abdominal pain, bloating, and constipation are common side effects that could complicate the clinical picture 7

Avoid empiric antibiotics:

• Empiric antimicrobial therapy is not recommended for acute watery diarrhea without recent international travel, fever, or bloody stools 1
• Antibiotics are contraindicated if there is any suspicion of STEC or Shiga toxin-producing E. coli, as they increase the risk of hemolytic uremic syndrome by up to 50% 6

Expected Timeline and Resolution

PEG-induced diarrhea is self-limited:

• Polyethylene glycol causes osmotic diarrhea by sequestering fluid in the bowel lumen 7, 8
• Diarrhea from bowel preparation typically resolves within 24-48 hours after stopping the laxative 4, 5
• The delayed onset of bowel movements (12 hours after ingestion) followed by persistent diarrhea at 21 hours post-ingestion is within the expected range for PEG preparations 3

Nutritional Management During Recovery

Resume oral intake appropriately:

• Continue oral hydration with ORS while diarrhea persists 1
• Once the patient can tolerate oral intake, resume an age-appropriate diet immediately after adequate rehydration 1
• Eliminate lactose-containing products temporarily, as osmotic laxatives can cause transient lactose intolerance 7

When to Escalate Care

Hospitalization or intensive monitoring is indicated if:

• Diarrhea persists beyond 48 hours after stopping PEG (suggesting the chronic diarrhea is the primary issue rather than PEG effect) 7
• Signs of severe dehydration develop despite oral rehydration attempts 1
• Fever (>38°C), severe abdominal cramping, bloody stools, or signs of sepsis emerge 7
• Laboratory abnormalities show significant electrolyte disturbances, elevated BUN/creatinine, or hemoconcentration 6

Common Pitfalls to Avoid

Do not withhold ORS in favor of IV fluids for mild-to-moderate dehydration:

• ORS is equally effective as IV fluids and avoids complications of IV access 1

Do not assume this is simply "bowel prep diarrhea" without considering the underlying chronic diarrhea:

• This patient has a 3-year history of chronic diarrhea that requires diagnostic evaluation via capsule endoscopy 7
• The PEG preparation may have exacerbated her baseline condition 8

Do not prescribe loperamide to "stop the diarrhea" before the capsule endoscopy:

• This could mask important diagnostic findings and potentially worsen outcomes if inflammatory or infectious causes are present 7, 1

Do not continue or repeat PEG dosing:

• The FDA label explicitly states to stop use if diarrhea develops 2
• Overuse of osmotic laxatives can lead to dehydration, hypernatremia, and electrolyte disturbances 7

Disposition and Follow-Up

The patient can be managed as an outpatient if:

• Mild-to-moderate dehydration is successfully corrected with ORS 1
• The patient tolerates oral intake without vomiting 1
• No signs of severe dehydration, sepsis, or electrolyte abnormalities are present 7, 1
• Reliable follow-up is available before the scheduled capsule endoscopy 1

Proceed with capsule endoscopy as scheduled once:

• Diarrhea resolves or significantly improves (typically within 24-48 hours) 4, 5
• The patient is adequately hydrated and can tolerate oral intake 1
• No contraindications to the procedure have emerged 3