What are some alternatives to Myrbetriq (mirabegron) and Tolterodine that are less likely to cause constipation?

Alternatives to Myrbetriq and Tolterodine with Lower Risk of Constipation

For patients experiencing constipation with mirabegron (Myrbetriq) or tolterodine, trospium is the best alternative medication for overactive bladder due to its lower risk of constipation while maintaining efficacy. 1

Comparison of OAB Medications and Their Constipation Risk

Beta-3 Agonists

• Mirabegron (Myrbetriq)
  • While generally better tolerated than antimuscarinics, it can still cause constipation in some patients
  • Associated with nasopharyngitis and gastrointestinal disorders rather than typical anticholinergic side effects 2

Antimuscarinic Agents with Lower Constipation Risk

1. Trospium

   • Water-soluble structure makes it less likely to enter the central nervous system 3
   • While it can cause constipation (reported in clinical trials), the incidence is lower than with other antimuscarinics 2
   • Particularly good option for elderly patients due to reduced cognitive effects 1

2. Darifenacin

   • Has a risk for discontinuation due to adverse effects similar to placebo 2
   • More selective for M3 receptors in the bladder, which theoretically should reduce systemic side effects 4
   • However, still has potential for constipation

3. Solifenacin

   • Associated with the lowest risk for discontinuation due to adverse effects among antimuscarinics 2, 1
   • Better tolerated than immediate-release oxybutynin but still has constipation as a potential side effect 3

Agents to Avoid Due to High Constipation Risk

• Oxybutynin

  • Highest risk for discontinuation due to adverse effects 2
  • Constipation reported in 15.1% of patients 1
  • Consider transdermal formulations if oral side effects are intolerable 1

• Fesoterodine

  • Higher rates of adverse effects than tolterodine 2
  • Dry mouth and constipation are common side effects

Decision Algorithm for Selecting an Alternative

1. First Choice: Trospium

   • Best option for patients specifically concerned about constipation
   • Water-soluble structure reduces CNS penetration
   • Effective for improving urinary incontinence 2

2. Second Choice: Darifenacin

   • Risk for discontinuation due to adverse effects similar to placebo
   • M3-selective receptor antagonist
   • May be better tolerated in patients sensitive to anticholinergic effects

3. Third Choice: Solifenacin

   • Lowest risk for discontinuation due to adverse effects among antimuscarinics
   • Effective for improving urinary symptoms
   • Consider if trospium and darifenacin are not tolerated or available

Management Strategies to Minimize Constipation

• Start with lower doses and titrate up as tolerated
• Ensure adequate hydration and fiber intake
• Consider combination with lifestyle modifications:
  • Pelvic floor muscle training
  • Bladder training
  • Weight loss if applicable 2

Important Considerations

• If constipation persists despite trying different antimuscarinic agents, consider non-pharmacological approaches such as pelvic floor muscle training and bladder training 2
• For elderly patients, be particularly cautious with antimuscarinic agents due to increased risk of cognitive impairment 1
• Monitor for signs of urinary retention, especially in patients with bladder outlet obstruction 1

Constipation is a common side effect with most OAB medications, but trospium appears to offer the best balance of efficacy with reduced constipation risk compared to mirabegron and tolterodine.