What is bladder Botox (onabotulinumtoxinA) and how does it work?

Bladder Botox (OnabotulinumtoxinA): A Third-Line Treatment for Overactive Bladder

Intradetrusor onabotulinumtoxinA (100 U) is a standard third-line treatment option for carefully selected patients with overactive bladder who have failed first-line behavioral therapy and second-line pharmacologic treatments. 1

What is Bladder Botox?

Bladder Botox (onabotulinumtoxinA) is a prescription medication that is injected directly into the bladder muscle (detrusor) to treat:

• Overactive bladder symptoms (strong urge to urinate, frequency, urgency, and urge incontinence) in adults when anticholinergic medications don't work well enough or can't be taken
• Urinary incontinence in adults with overactive bladder due to neurologic disease
• Overactive bladder due to neurologic disease in children 5 years and older when anticholinergics are ineffective or not tolerated 2

How Does Bladder Botox Work?

Bladder Botox works through a specific mechanism:

• It blocks neuromuscular transmission by binding to nerve terminals
• Once inside nerve terminals, it inhibits the release of acetylcholine (a neurotransmitter)
• This occurs as the neurotoxin cleaves SNAP-25, a protein essential for acetylcholine release
• The result is partial chemical denervation of the bladder muscle, reducing overactivity
• This leads to decreased bladder contractions and reduced urinary urgency and frequency 2

The effects are temporary, typically lasting 6-9 months, after which the treatment needs to be repeated 3.

Patient Selection and Treatment Algorithm

The AUA/SUFU guidelines provide a clear treatment algorithm for overactive bladder:

1. First-line treatment: Behavioral therapy (8-12 weeks)
2. Second-line treatment: Anticholinergic medications (4-8 weeks)
3. Third-line treatment: For patients who fail first and second-line treatments:
   • OnabotulinumtoxinA (100 U) injections
   • Sacral neuromodulation
   • Peripheral tibial nerve stimulation 1

Patient Selection Criteria for Bladder Botox:

Patients should be:

• Refractory to first and second-line treatments
• Thoroughly counseled about risks and benefits
• Able and willing to return for post-void residual (PVR) evaluation
• Able and willing to perform self-catheterization if necessary 1

Administration and Dosing

• Standard dose: 100 U of onabotulinumtoxinA (FDA approved dose)
• Administration: Cystoscopic-guided injection at approximately 20 sites in the detrusor muscle
• Injection sites: Distributed throughout the bladder, avoiding the trigone
• Volume: Typically 1 mL per injection site 1, 3

Efficacy

Bladder Botox has demonstrated significant efficacy in clinical trials:

• Decreases daily frequency of urinary incontinence episodes (-2.65 vs -0.87 for placebo)
• Approximately 23% of patients become completely continent
• 60.8% of patients report positive treatment benefit (vs 29.2% for placebo)
• Improves quality of life across multiple measures 4

Follow-up and Monitoring

1. Pre-treatment: Measure post-void residual (PVR) to establish baseline bladder emptying 1
2. Post-treatment: Evaluate patients approximately 2 weeks after injection to:
   • Assess symptom improvement
   • Check post-void residual to rule out urinary retention
   • Evaluate for urinary tract infection if symptoms haven't improved 1
3. Medication management: Consider discontinuing oral OAB medications if good response is achieved 1
4. Retreatment: Plan for repeat injections when efficacy diminishes (typically every 9-11 months) 3

Potential Adverse Effects

Common adverse effects include:

• Urinary tract infection (most common)
• Urinary retention requiring clean intermittent catheterization (5.4% in idiopathic OAB, higher in neurogenic cases)
• Hematuria (usually mild and self-limiting)
• Rarely, systemic effects such as muscle weakness 1, 4

Important Considerations and Cautions

• Pre-injection assessment: PVR should be measured prior to treatment
• Exclusion criteria: Caution should be used in patients with PVR > 100-200 mL
• Patient counseling: Patients must understand and accept the possibility of needing to perform self-catheterization
• Duration of effect: Effects diminish over time, requiring repeat injections
• Contraindications: Active urinary tract infection, inability to empty bladder (for those not routinely catheterizing) 1, 2

Special Populations

• Neurogenic detrusor overactivity: Botox has a strong recommendation (Grade A evidence) for patients with spinal cord injury and multiple sclerosis 5
• Children: Has been used successfully in children with refractory overactive bladder, though with varying protocols 6
• Elderly: Limited specific data, but treatment principles remain similar with potentially increased attention to post-void residual monitoring

Bladder Botox represents an important treatment option for patients with overactive bladder who have failed conservative and pharmacological management, offering significant improvements in symptoms and quality of life.