How to manage urinary retention in a patient on amitriptyline (tricyclic antidepressant)?

Management of Urinary Retention in a Patient on Amitriptyline

Amitriptyline should be discontinued or reduced in dosage as the first step in managing urinary retention, as tricyclic antidepressants are known to cause anticholinergic side effects including urinary retention, particularly in elderly patients. 1

Mechanism of Amitriptyline-Induced Urinary Retention

• Tricyclic antidepressants (TCAs) like amitriptyline have significant anticholinergic activity that can impair bladder function 2
• Peripheral anticholinergic effects include urinary retention, constipation, dry mouth, blurred vision, and exacerbation of narrow-angle glaucoma 1
• Elderly patients are particularly sensitive to these anticholinergic side effects 1, 3
• Drug-induced urinary retention may account for up to 10% of all urinary retention episodes 3

Assessment of Urinary Retention

• Exclude post-void residual urine, dysfunctional voiding, or low voiding frequency by performing a frequency-volume chart and ultrasound measurement of post-void residual urine 2
• Assess for other contributing factors:
  • Exclude or treat constipation, which can worsen urinary symptoms 2
  • Check for concomitant medications with anticholinergic properties that could compound the effect 3
  • Consider underlying conditions such as benign prostatic hyperplasia that increase risk 3

Management Algorithm

1. First-line approach: Medication adjustment

   • Discontinue amitriptyline if possible or reduce to lowest effective dose 3
   • Consider switching to an antidepressant with lower anticholinergic burden:
     • SSRIs have lower rates of urinary retention (0.025%) compared to TCAs (reported up to 17.6% with imipramine) 4
     • SNRIs like duloxetine have shown very low rates of urinary retention (none reported in 958 women in clinical trials) 5

2. Acute management if retention is severe

   • Urinary catheterization may be necessary for acute urinary retention 3
   • After catheterization, monitor for return of normal voiding function following medication adjustment 3

3. Pharmacological interventions if medication change is not possible

   • Alpha-blockers may help relieve bladder outlet obstruction if amitriptyline must be continued 2
   • Bethanechol (a cholinergic agent) may be considered to counteract anticholinergic effects, though evidence is limited 3

4. Non-pharmacological approaches

   • Institute sound, regular voiding habits 2
   • Scheduled voiding attempts may help prevent retention 2
   • Avoid excessive fluid intake in the evening 2

Special Considerations

• Elderly patients require particular caution:

  • Start with lower doses of amitriptyline if it must be used 1
  • Monitor closely for development of urinary symptoms 1
  • These patients are at higher risk due to age-related changes in bladder function and potential comorbidities 3

• Combination therapy risks:

  • Avoid combining amitriptyline with other medications that have anticholinergic properties 1
  • Paralytic ileus may occur when tricyclic antidepressants are administered with other anticholinergic-type drugs 1

Follow-up and Monitoring

• Monitor for resolution of symptoms after medication adjustment 3
• If symptoms persist despite medication changes, consider urological consultation for further evaluation 2
• Normal micturition typically resumes after discontinuation of the causative agent, as demonstrated in case reports 6, 7