What to do with a patient on nortriptyline (tricyclic antidepressant) for Irritable Bowel Syndrome (IBS) who develops transient left-sided periorbital paresthesia?

Management of Periorbital Paresthesia in a Patient on Nortriptyline for IBS

The patient experiencing transient left-sided periorbital paresthesia while on nortriptyline for IBS should discontinue the medication immediately due to the risk of serious neurological complications, and alternative treatment options should be considered.

Understanding the Clinical Concern

Periorbital paresthesia (abnormal sensation around the eye) while on a tricyclic antidepressant (TCA) like nortriptyline is concerning for several reasons:

• This symptom may represent an early warning sign of TCA toxicity, which can progress to more serious neurological and cardiac complications
• TCAs have a narrow therapeutic window and can cause significant side effects even at therapeutic doses
• Neurological symptoms like paresthesia can precede more serious adverse effects

Assessment and Management Algorithm

1. Immediate Actions

• Discontinue nortriptyline - Even transient neurological symptoms warrant medication discontinuation due to risk of progression
• Perform focused neurological examination to assess for:
  • Other neurological deficits
  • Visual changes
  • Cardiac symptoms (tachycardia, arrhythmias)
  • Mental status changes

2. Evaluate for TCA Toxicity

• Check vital signs with particular attention to:
  • Heart rate and rhythm (tachycardia is common in TCA toxicity)
  • Blood pressure (hypotension can occur in severe cases)
  • Respiratory rate
• Consider ECG to evaluate for QT prolongation or other conduction abnormalities 1
• Assess for other anticholinergic symptoms:
  • Dry mouth, blurred vision, urinary retention, constipation

3. Alternative Treatment Options for IBS

After discontinuing nortriptyline, consider these evidence-based alternatives:

For IBS with Diarrhea:

• Secondary amine TCAs at lower doses (if no contraindication based on the adverse event):
  • Desipramine 25-75 mg/day 2, 3
  • Starting at 10 mg at night and gradually titrating 3
• 5-HT3 receptor antagonists:
  • Ondansetron 4 mg with dose titration allowed up to two tablets three times daily 4
  • Shown to improve stool consistency, urgency, and frequency

For IBS with Constipation:

• Linaclotide 290 mcg once daily 2
• Tenapanor 50 mg twice daily 2
• Fiber supplementation 3

For IBS with Mixed Symptoms:

• Antispasmodics 2
• Peppermint oil 2, 3
• Mirtazapine 7.5-30 mg/day 2, 3

Important Considerations and Caveats

Risk Factors for TCA Adverse Effects

• Age ≥50 years (increased sensitivity to side effects) 5
• Concurrent medications that may interact with TCAs
• Pre-existing cardiac or neurological conditions
• Higher doses of medication

Monitoring for New Treatment

• Follow up within 1-2 weeks after starting alternative therapy
• Monitor for improvement in IBS symptoms and absence of neurological symptoms
• Titrate medication doses slowly based on response and tolerability 3

Patient Education

• Explain that TCAs, while effective for IBS (RR 0.67 for global symptom relief) 6, can cause neurological side effects
• Emphasize the importance of reporting any new neurological symptoms immediately
• Discuss the mechanism of action of alternative treatments

Conclusion

Periorbital paresthesia in a patient taking nortriptyline requires immediate discontinuation of the medication due to the risk of progression to more serious neurological or cardiac complications. Alternative treatments for IBS should be selected based on predominant symptoms, with careful monitoring for efficacy and side effects.