What are the treatment options for an elderly man with overactive bladder, including medications such as antimuscarinic agents (e.g. oxybutynin) or beta-3 adrenergic agonists (e.g. mirabegron)?

Treatment of Overactive Bladder in Elderly Men

Begin with behavioral therapies immediately (bladder training, pelvic floor exercises, fluid management), then add mirabegron 25-50 mg daily as the preferred pharmacologic agent over antimuscarinics due to significantly lower cognitive risk and anticholinergic burden in elderly patients. 1, 2, 3

First-Line Treatment: Behavioral Interventions (Start Immediately)

All elderly men with overactive bladder should begin behavioral therapies as first-line treatment, as they are as effective as antimuscarinic medications but carry zero risk and no drug interactions. 4

Specific behavioral interventions include:

• Bladder training and delayed voiding: Practice postponing urination when urgency occurs, gradually extending intervals between voids over 8-12 weeks. 4, 3

• Fluid management: Reduce total daily fluid intake by 25%, which decreases frequency and urgency; particular attention to evening fluid restriction to reduce nocturia. 4, 3

• Caffeine and alcohol elimination: Remove bladder irritants from the diet, as caffeine reduction reduces voiding frequency. 4, 3

• Pelvic floor muscle training: Strengthening exercises for urge suppression and improved bladder control. 4, 3

• Weight loss if obese: Even 8% weight reduction decreases urgency incontinence episodes by 42%. 4, 3

Second-Line Treatment: Pharmacologic Management

Preferred Agent: Beta-3 Adrenergic Agonist

Mirabegron is the preferred first pharmacologic choice for elderly men due to:

• Efficacy comparable to antimuscarinics with significantly lower incidence of anticholinergic side effects. 4, 1

• Lower risk of cognitive impairment compared to antimuscarinics—critically important in elderly patients. 1, 2, 3

• Fewer drug interactions compared to antimuscarinics. 1, 5

Dosing for mirabegron:

• Start at 25 mg orally once daily. 5
• After 4-8 weeks, may increase to 50 mg once daily if inadequate response. 5
• Take with water, swallow whole (do not crush or chew). 5

Alternative Agents: Antimuscarinics (Second Choice)

If mirabegron fails, is contraindicated, or unavailable, consider oral antimuscarinics as second-line options. 4

Available antimuscarinics include (no hierarchy in efficacy): darifenacin, fesoterodine, oxybutynin, solifenacin, tolterodine, or trospium. 4

Among antimuscarinics, if needed:

• Solifenacin has the lowest risk for discontinuation due to adverse effects. 2
• Transdermal oxybutynin may be offered if dry mouth is a concern with oral agents. 4

Critical Safety Considerations in Elderly Men

Before Starting Any Antimuscarinic:

Absolute contraindications:

• Narrow-angle glaucoma (unless approved by ophthalmologist). 4
• Impaired gastric emptying. 4
• History of urinary retention. 4

Measure post-void residual (PVR) before starting antimuscarinics if patient has:

• Emptying symptoms. 3
• History of urinary retention. 3
• Enlarged prostate. 3
• Neurologic disorders. 3
• Prior prostate surgery. 3
• Long-standing diabetes. 3

Use extreme caution with antimuscarinics if PVR >250-300 mL. 3

Special Considerations for Frail Elderly Men:

Frail patients (those with mobility deficits, slow gait speed, difficulty rising from sitting, unexplained weight loss/weakness, or cognitive deficits) have lower therapeutic index and higher adverse event profile with OAB medications. 4

In frail elderly men:

• Mirabegron is preferred over antimuscarinics due to lack of anticholinergic cognitive effects. 4, 2
• If antimuscarinics cannot be tolerated, focus on behavioral strategies including prompted voiding and fluid management. 4

Cognitive Risk Warning:

Antimuscarinic medications are associated with impaired cognitive function and potential incident dementia risk that may be cumulative and dose-dependent. 4, 2

This makes mirabegron the strongly preferred pharmacologic option in elderly men. 1, 2, 3

Special Consideration: Concomitant Benign Prostatic Hyperplasia (BPH)

If the elderly man has both overactive bladder and bladder outlet obstruction from BPH:

• First assess for obstruction: Check flow study and post-void residual. 4

• If coexisting OAB and BOO symptoms: Consider combination therapy with alpha-blocker (e.g., tamsulosin) plus antimuscarinic, which has demonstrated safety and efficacy. 4

• If BOO symptoms predominate: Alpha-1 adrenergic blocking agents are treatment of choice. 4

• If prostate enlarged or PSA >1.5 ng/mL: Combination therapy with alpha-blocker plus 5-alpha-reductase inhibitor shows highest efficacy. 4

Combination Therapy Strategy

Behavioral therapies may be combined with pharmacologic management to optimize outcomes. 4

Initiating behavioral and drug therapy simultaneously may improve outcomes including frequency, voided volume, incontinence, and symptom distress. 4

Treatment Adjustment Algorithm

If inadequate symptom control or unacceptable adverse events occur:

1. Allow 4-8 weeks to assess antimuscarinic efficacy (or 2-4 weeks for alpha-blockers if treating concurrent BOO). 4, 3

2. Consider dose modification of current medication. 4

3. Switch to a different antimuscarinic if using one. 4

4. Switch to mirabegron (beta-3 agonist) if on antimuscarinic. 4

5. Do not abandon antimuscarinic therapy after single agent failure—try alternative agents before declaring class failure. 4

Monitoring Requirements

• Blood pressure monitoring: Mirabegron can increase blood pressure; monitor periodically, especially in hypertensive patients. 5

• Post-void residual monitoring: If using antimuscarinics in high-risk patients. 4, 3

• Annual follow-up: Assess treatment efficacy, symptom progression, and development of complications. 4, 3

• Monitor for adverse effects: Constipation, dry mouth, urinary retention, cognitive changes (with antimuscarinics). 4, 2

Common Pitfalls to Avoid

• Failing to start behavioral therapies first or simultaneously with medications—behavioral interventions are as effective as medications with zero risk. 4

• Using antimuscarinics as first-line pharmacologic therapy in elderly men—mirabegron should be preferred due to lower cognitive risk. 1, 2, 3

• Not assessing for bladder outlet obstruction in elderly men before starting antimuscarinics—risk of urinary retention. 4, 3

• Abandoning antimuscarinic class after single agent failure—different agents have different tolerability profiles. 4

• Ignoring drug interactions—mirabegron is a moderate CYP2D6 inhibitor and can increase levels of drugs like metoprolol, desipramine, and other CYP2D6 substrates. 5

• Not checking for narrow-angle glaucoma, gastric emptying problems, or urinary retention history before prescribing antimuscarinics—these are contraindications. 4

Referral to Specialist

Refer to urology if patient fails behavioral and pharmacologic therapy (defined as failure of 8-12 weeks of behavioral therapy plus trial of at least one medication for 4-8 weeks) and desires additional therapy. 4

Third-line options available through specialist include botulinum toxin injections, sacral neuromodulation, or peripheral tibial nerve stimulation. 4, 3