How to manage fecal incontinence in patients taking gabapentin (Neurontin)?

Managing Fecal Incontinence in Patients Taking Gabapentin

If gabapentin is causing fecal incontinence, discontinue the medication immediately, as this is a reversible adverse effect that resolves within days of withdrawal.

Understanding Gabapentin's Gastrointestinal Effects

While gabapentin is listed as an analgesic option for intestinal dysmotility 1, it can paradoxically cause significant bowel dysfunction. The drug has documented effects on continence mechanisms:

• Gabapentin causes urinary incontinence that completely resolves within 2 days of discontinuation and recurs upon rechallenge 2
• Pregabalin (a related gabapentinoid) causes severe, disabling constipation in 7.5% of patients, with symptoms appearing within 1-2 weeks and being dose-dependent 3
• The constipation from pregabalin is the most frequent adverse effect requiring drug withdrawal (6.3% of patients) and resolves only upon discontinuation 3

Immediate Management Algorithm

Step 1: Discontinue Gabapentin

• Stop gabapentin immediately if temporal relationship suggests causation (symptoms began after starting drug) 3, 2
• Expect resolution within 2-7 days based on related gabapentinoid data 3, 2
• Document the response to confirm drug causation 2

Step 2: Control Diarrhea While Awaiting Resolution

If fecal incontinence involves loose stools, initiate antidiarrheal therapy:

• Loperamide is first-line (opioid agonist without central effects) 1
• Ondansetron (5-HT3 antagonist) as alternative, though it may cause constipation 1
• Avoid codeine phosphate due to central sedation and dependence risk 1

Step 3: Alternative Analgesic Selection

Replace gabapentin with safer neuropathic pain agents:

• Low-dose amitriptyline (tricyclic antidepressant) 1
• Duloxetine (SNRI) 1
• Pregabalin should also be avoided given similar mechanism and documented severe constipation 3

If Gabapentin Cannot Be Discontinued

When gabapentin is essential for pain control and cannot be stopped:

Symptomatic Management of Fecal Incontinence

For liquid/loose stool incontinence:

• Loperamide 2-4 mg as needed, up to 16 mg daily 1
• Scheduled toileting and behavioral techniques 4
• Pelvic floor exercises (restore continence in up to 25%) 4

For urgency-related incontinence:

• Biofeedback therapy produces satisfaction in up to 76% and continence in 55% of patients 4
• Requires skilled therapist but is first-line after conservative management fails 4

For refractory cases:

• Sacral nerve stimulation produces ≥50% reduction in fecal incontinence frequency in 73% of patients 4
• Sphincteroplasty if structural defect identified on endosonography 5, 4

Critical Diagnostic Considerations

Before attributing incontinence solely to gabapentin:

• Anorectal manometry to assess sphincter pressures and rectal sensation 5
• Anal endosonography to define sphincter anatomy and identify obstetric trauma 5
• Rule out bacterial overgrowth if patient has intestinal dysmotility 1
• Assess stool consistency—control of diarrhea should be attempted first regardless of cause 5

Common Pitfalls to Avoid

• Do not continue gabapentin if incontinence is severe and disabling—the drug's gastrointestinal effects are entirely reversible 3
• Do not perform unnecessary investigations before attempting drug withdrawal, as this adverse effect resolves quickly 3
• Do not use combination gabapentinoids (gabapentin plus pregabalin), as both cause bowel dysfunction 1, 3
• Monitor for serotonin syndrome if combining alternative agents like duloxetine with SSRIs 1