Can Gabapentin Cause Fecal Incontinence and Diarrhea?
Yes, gabapentin can cause both fecal incontinence and diarrhea, though these are uncommon adverse effects. According to the FDA drug label, diarrhea occurs in 6% of gabapentin-treated patients (versus 3% with placebo), and case reports document incontinence of bowel and bladder as a recognized adverse effect 1, 2.
Direct Evidence from FDA Labeling
The official FDA prescribing information explicitly lists:
- Diarrhea: Occurs in 6% of patients taking gabapentin versus 3% on placebo in controlled trials 1
- Bowel and bladder incontinence: Documented in open trials and case reports as a less frequent but recognized side effect 2, 1
These gastrointestinal effects are dose-dependent and more likely at higher doses (>900 mg/day) 2.
Context with Epidural/Facet Injections
The combination of gabapentin with recent lumbar epidural or facet injections does not increase the risk of these gastrointestinal side effects. Multiple studies examining gabapentin use after epidural steroid injections for lumbar radiculopathy found no significant gastrointestinal adverse events 3, 4, 5, 6. The epidural injection itself does not cause bowel dysfunction—guidelines confirm these procedures provide only temporary symptomatic relief without systemic gastrointestinal effects 7, 8, 9.
Clinical Considerations
If fecal incontinence or diarrhea develops after starting gabapentin:
- Timing matters: Symptoms typically emerge within days to weeks of initiation or dose escalation
- Dose relationship: Higher doses (>900 mg/day) carry greater risk 2
- Reversibility: These effects resolve with dose reduction or discontinuation 1
- Alternative causes: Rule out other medications (opioids cause constipation, not diarrhea), dietary changes, or underlying bowel pathology
Mechanism
Gabapentin's gastrointestinal effects likely result from:
- Modulation of calcium channels affecting gut motility
- Central nervous system effects on autonomic regulation of bowel function
- Individual patient susceptibility factors
Important caveat: While gabapentin can cause these symptoms, they remain relatively uncommon (diarrhea in 6%, incontinence even rarer). The drug's primary adverse effects are neurological—dizziness (28%), somnolence (21%), and ataxia (13%)—which occur far more frequently 1.
Practical Management
If gabapentin is suspected:
- Reduce the dose to 300-600 mg/day or discontinue temporarily
- Monitor for resolution within 3-7 days
- Consider alternative neuropathic agents (pregabalin, duloxetine) if gabapentin must be discontinued
- Avoid attributing symptoms to the epidural injection, which has no mechanism to cause delayed bowel dysfunction 7, 8
The epidural or facet injection itself is not causative—these procedures use local anesthetics and steroids that do not produce systemic gastrointestinal effects 9.