What are the first-line medications for treating Overactive Bladder (OAB)?

First-Line Medications for Overactive Bladder (OAB)

Beta-3 adrenoceptor agonists, such as mirabegron, are the preferred first-line pharmacological treatment for overactive bladder (OAB), followed by antimuscarinic medications if needed. 1, 2

Pharmacological Treatment Algorithm

First-Line Therapy

1. Beta-3 adrenoceptor agonists
   • Mirabegron (Myrbetriq)
     • Starting dose: 25 mg orally once daily 3
     • May increase to 50 mg once daily after 4-8 weeks if needed 3
     • Advantages:
       • Fewer cognitive side effects than antimuscarinics 1
       • Effective for reducing urinary urgency, frequency, and incontinence 2
     • Dosage adjustments:
       • For renal impairment (eGFR 15-29 mL/min): maximum 25 mg daily 3
       • For moderate hepatic impairment (Child-Pugh B): maximum 25 mg daily 3

Second-Line Therapy

1. Antimuscarinic medications (if beta-3 agonists are ineffective or contraindicated)
   • Options include:
     • Solifenacin
     • Darifenacin
     • Tolterodine (immediate and extended release)
     • Trospium (immediate and extended release)
     • Oxybutynin (immediate release, extended release, transdermal)
   • Important caution: Use antimuscarinics with extreme caution in:
     • Elderly patients (risk of cognitive effects) 1, 2
     • Patients with narrow-angle glaucoma 1
     • Patients with impaired gastric emptying 1
     • Patients with history of urinary retention 1

Combination Therapy

• Consider combination therapy with an antimuscarinic and beta-3 adrenoceptor agonist for patients refractory to monotherapy 1
• Most evidence supports combination of solifenacin (5 mg) with mirabegron (25 or 50 mg) 1

Behavioral Modifications (Adjunct to Medication)

• Implement alongside pharmacotherapy:
  • Timed voiding schedule (start with 1-2 hour intervals) 2
  • Reduce fluid intake by approximately 25% 2
  • Eliminate or significantly reduce caffeine 2
  • Weight loss (8% weight reduction can decrease incontinence episodes by 47% in overweight patients) 2
  • Pelvic floor muscle training 2

Monitoring and Follow-up

• Assess treatment efficacy:
  • For mirabegron: within 8 weeks (success defined as ≥50% reduction in urinary incontinence episodes) 2
  • For antimuscarinics: after 2-4 weeks 2
• Annual follow-up to reassess symptoms and treatment efficacy 2

Third-Line Options (for refractory cases)

For patients who fail or cannot tolerate first and second-line therapies:

• Intradetrusor onabotulinumtoxinA (100 U) 1, 2
• Sacral neuromodulation (SNS) 1, 2
• Peripheral tibial nerve stimulation (PTNS) 1, 2

Common Pitfalls and Caveats

1. Cognitive effects with antimuscarinics: Avoid in patients with existing cognitive impairment; use beta-3 agonists instead 1, 2
2. Urinary retention: Check post-void residual; consider dose reduction or discontinuation if >200 mL 2
3. Long-term adherence: Treatment effects are only maintained as long as therapy is continued; patient education is crucial 2
4. Side effect management:
   • For dry mouth: Consider extended-release formulations or transdermal applications 2
   • For constipation: Increase fluid and fiber intake; consider stool softeners 2

Remember that while pharmacotherapy is effective, behavioral therapies can be equally effective with no risk of adverse effects and should be implemented concurrently with medication 2.