Adult with abdominal pain and two‑day constipation while on amoxicillin for otitis media, how should I manage him?

Management of Abdominal Pain and Constipation During Amoxicillin Therapy for Otitis Media

Stop the amoxicillin immediately and initiate symptomatic management with osmotic laxatives for the constipation, while monitoring for signs of antibiotic-associated colitis.

Immediate Assessment and Antibiotic Management

Discontinue Amoxicillin

• Amoxicillin can cause antibiotic-associated hemorrhagic colitis (AAHC), presenting with abdominal pain, diarrhea, and bloody stools, though constipation may represent an earlier or variant presentation of antibiotic-associated gastrointestinal disturbance 1.
• The temporal relationship between amoxicillin use and symptom onset strongly suggests drug-related pathology 1.
• Continuing the antibiotic risks progression to more severe colitis 1.

Evaluate Otitis Media Treatment Status

• If the patient has completed at least 5–7 days of amoxicillin for otitis media and symptoms have improved, stopping the antibiotic is appropriate as shorter courses (5–7 days) are effective in adults and older children 2.
• If the ear infection requires continued treatment, switch to a non-penicillin alternative such as cefdinir (14 mg/kg/day), cefuroxime (30 mg/kg/day), or cefpodoxime (10 mg/kg/day) for the remaining duration 2, 3.

Constipation Management

First-Line Laxative Therapy

• Initiate polyethylene glycol (PEG) as the first-line osmotic laxative, which is effective for constipation, inexpensive, widely available, and well-tolerated 4.
• Osmotic laxatives increase water in the large bowel and are preferred over stimulant laxatives initially 4.
• Dosing: Adults typically receive 17 grams (one capful) of PEG 3350 dissolved in 8 ounces of water once daily, adjusted based on response 4.

Escalation if Inadequate Response

• If PEG alone is insufficient after 48–72 hours, add a stimulant laxative such as senna or bisacodyl 4.
• Stimulant laxatives increase intestinal motility but may cause abdominal cramping 4.
• Avoid chronic use of stimulant laxatives, as prolonged usage was historically thought to damage the intestine, though clinical evidence does not support this concern 4.

Adjunctive Measures

• Ensure adequate fluid intake to support osmotic laxative efficacy 4.
• Dietary fiber modification: If the patient is not malnourished, consider adding soluble fiber (e.g., psyllium), though avoid in patients with suspected bowel dysmotility 4.

Red Flags Requiring Urgent Evaluation

Signs of Antibiotic-Associated Colitis

• Monitor for progression to bloody stools, severe abdominal pain, fever, or hemodynamic instability, which would indicate AAHC requiring hospitalization 1.
• If these develop, obtain stool studies including Clostridioides difficile testing, stool culture, and consider colonoscopy 1.
• Treatment for confirmed AAHC includes discontinuation of the offending antibiotic, probiotics (e.g., Bifidobacterium quadruplex), and supportive care 1.

Mechanical Obstruction

• Evaluate for mechanical obstruction if the patient develops severe pain, visible peristalsis, or vomiting 4.
• Obtain abdominal CT if obstruction is suspected, as a distinct transition point between dilated and normal bowel suggests organic obstruction rather than functional constipation 4.

Gastrointestinal Symptom Management

Pain Control

• Use antispasmodics such as hyoscine butylbromide or dicycloverine hydrochloride for cramping abdominal pain 4.
• Hyoscine butylbromide is poorly absorbed orally; intramuscular preparations may be more effective for long-term use 4.
• Peppermint oil may reduce abdominal distension and discomfort 4.

Nausea Management

• If nausea is prominent, use ondansetron (a 5-HT3 antagonist) rather than metoclopramide or domperidone, as the latter are no longer recommended for long-term use 4.
• Avoid cyclizine, which has addictive potential and is not recommended for prolonged use 4.
• Be aware that ondansetron can worsen constipation 4.

Follow-Up and Reassessment

Timeline for Improvement

• Reassess within 48–72 hours to confirm symptom resolution and ensure the ear infection is adequately treated 2, 3.
• Constipation should improve within 24–48 hours of initiating PEG 4.

Persistent Symptoms

• If abdominal pain and constipation persist beyond 72 hours despite laxative therapy, consider alternative diagnoses including irritable bowel syndrome, functional constipation, or opioid-induced bowel dysfunction (if the patient is taking pain medications) 4.
• Obtain abdominal imaging (CT scan) if symptoms worsen or if there is concern for complications 4.

Common Pitfalls to Avoid

• Do not continue amoxicillin in the setting of new gastrointestinal symptoms, as this risks progression to severe colitis 1.
• Do not use stimulant laxatives as first-line therapy; osmotic laxatives are preferred initially 4.
• Do not prescribe opioids for abdominal pain, as they worsen constipation and can lead to narcotic bowel syndrome 4.
• Do not assume all antibiotic-associated diarrhea is C. difficile; amoxicillin can cause hemorrhagic colitis through other mechanisms 1.
• Do not overlook the need to complete otitis media treatment; ensure an alternative antibiotic is prescribed if the infection is not fully resolved 2, 3.