Is stress incontinence treated the same as Overactive Bladder (OAB) with beta 3 agonists, such as mirabegron (mirabegron)?

No, Stress Incontinence and OAB Are Treated Differently—Beta-3 Agonists Are NOT Used for Stress Incontinence

Pharmacologic therapy, including beta-3 agonists like mirabegron, is not recommended for stress urinary incontinence and should only be used for overactive bladder (urgency urinary incontinence) after behavioral therapies have failed. 1

Key Distinction Between These Conditions

Stress incontinence involves involuntary urine leakage with physical exertion (coughing, sneezing, exercise) due to urethral sphincter weakness, while overactive bladder is characterized by urgency with or without urge incontinence due to detrusor overactivity 2. These are fundamentally different pathophysiologic mechanisms requiring distinct treatment approaches.

Treatment Algorithm for Stress Incontinence

First-Line Treatment

• Pelvic floor muscle training (PFMT) is the recommended first-line treatment with strong evidence and high-quality data 1
• Non-pharmacological approaches should always be prioritized over medications 1

Pharmacologic Options (Limited)

• Pharmacologic therapy is NOT recommended for stress urinary incontinence based on strong evidence 1
• Duloxetine has limited efficacy (NNTB of 13) and did not show statistically significant improvement compared to placebo 1
• For postmenopausal women specifically, vaginal estrogen tablets or ovules may be considered (NNTB of 5) 1

Critical Pitfall

Beta-3 agonists have no role in treating pure stress incontinence. Mirabegron and vibegron work by relaxing the detrusor muscle during bladder filling, which addresses urgency symptoms but does nothing for urethral sphincter incompetence 2, 3

Treatment Algorithm for Overactive Bladder

First-Line Treatment

• Bladder training is the recommended first-line treatment with strong recommendation and moderate-quality evidence 1
• Non-pharmacological approaches including behavioral modification and pelvic floor exercises should be attempted first 4

Second-Line Pharmacologic Treatment

When bladder training fails, pharmacologic therapy is appropriate 1:

Preferred agents based on tolerability:

• Solifenacin has the lowest risk for discontinuation due to adverse effects 1
• Darifenacin and tolterodine have discontinuation rates similar to placebo 1
• Mirabegron (beta-3 agonist) improves urinary incontinence (NNTB of 9) and achieves continence (NNTB of 12) 5
• Avoid oxybutynin due to highest discontinuation rates 1

Beta-3 Agonist Specifics

• Mirabegron 50 mg once daily reduces micturition episodes by an average of 2.5 per 24 hours and incontinence episodes by 0.81 per 24 hours 6
• Beta-3 agonists commonly cause nasopharyngitis and gastrointestinal disorders 1
• They have fewer drug interactions than antimuscarinics and lower cognitive effects, particularly important for elderly patients 5

Mixed Incontinence Considerations

When patients have both stress and urgency components (mixed incontinence):

• Combined PFMT with bladder training is the first-line treatment with strong recommendation 1
• If pharmacotherapy is needed, it should target the urgency component only 4
• One study showed mirabegron can be effective in females with OAB symptoms after surgical treatment for stress incontinence, but this addresses the OAB component, not the stress component 7

Important Clinical Caveat

If a patient presents with both BOO (bladder outlet obstruction) and OAB symptoms, combination therapy with alpha-blocker and antimuscarinic may be considered with increasing evidence of safety and efficacy, though this applies primarily to male patients 4. The treatment selection should be influenced by coexisting symptoms and clinical findings 4.