Discontinue Amitriptyline and Switch to Peppermint Oil
The bilateral foot pain worsening in the evening is likely a peripheral neuropathic side effect of amitriptyline and warrants immediate discontinuation of the medication. The temporal relationship between starting amitriptyline and developing new bilateral foot pain strongly suggests drug-induced peripheral neuropathy, which can occur with tricyclic antidepressants 1.
Rationale for Discontinuation
Amitriptyline's FDA labeling warns about neurological adverse effects, and while the drug has been used for decades in neuropathic pain, the evidence base is surprisingly weak 2. The development of new neuropathic symptoms (bilateral foot pain) while on a medication that affects peripheral nerves represents a clear harm that outweighs the modest benefit ("slightly better" abdominal pain). The risk-benefit ratio has shifted unfavorably—you're trading one pain syndrome for another, potentially more debilitating one.
The anticholinergic effects of amitriptyline can also persist or fluctuate throughout long-term treatment 3, and the drug carries risks of serious complications including CNS effects and cardiac arrhythmias 4.
Recommended Alternative: Peppermint Oil
For long-term management of abdominal pain, switch to peppermint oil as your primary antispasmodic agent. The 2022 AGA guidelines specifically recommend antispasmodics for IBS-related abdominal pain, and notably state that "of the antispasmodics studied, only hyoscine, dicyclomine, and peppermint oil are available in the United States" 5, 6.
Why Peppermint Oil Over Dicyclomine Long-Term:
- Peppermint oil can be used chronically without the same safety concerns as dicyclomine
- Dicyclomine's anticholinergic effects (dry mouth, dizziness, blurred vision) limit long-term tolerability 6, 7
- The FDA labeling for dicyclomine does not support extended continuous use 8
- Antispasmodics as a class showed significant improvement in abdominal pain (RR 0.74,95% CI 0.59-0.93) 5, 6
Dosing Strategy:
- Start peppermint oil (enteric-coated formulation) 0.2-0.4 mL three times daily, 30-60 minutes before meals
- This provides smooth muscle relaxation and reduces visceral hypersensitivity without systemic anticholinergic burden
- Can be used indefinitely for symptom control
Monitoring After Amitriptyline Discontinuation
Taper amitriptyline over 1-2 weeks (reduce by 25 mg every 3-4 days) rather than abrupt cessation to avoid withdrawal symptoms. The bilateral foot pain should begin improving within 2-4 weeks of complete discontinuation if it is indeed drug-induced peripheral neuropathy.
Red Flags to Watch:
- If foot pain persists beyond 4-6 weeks after stopping amitriptyline, consider alternative etiologies (diabetic neuropathy, B12 deficiency, other metabolic causes)
- Document baseline neurological exam now to track improvement
- The evening worsening pattern is consistent with medication-induced neuropathy but could also represent other pathology if it doesn't resolve
Alternative Consideration If Peppermint Oil Insufficient
If peppermint oil alone doesn't provide adequate relief after 4-6 weeks:
- Consider a trial of an SSRI (citalopram 20-40 mg daily) rather than returning to tricyclics 5, 6
- While SSRIs showed only "possible improvement" with low certainty evidence, they lack the peripheral neuropathic risks of amitriptyline
- SNRIs (duloxetine) may theoretically be more effective for visceral pain but lack IBS-specific trial data 5
The key principle: you cannot continue a medication that is causing new neuropathic pain while treating abdominal pain. The development of bilateral foot pain represents a clear adverse effect that compromises quality of life, and safer alternatives exist for managing functional abdominal pain.