Can mirabegron be used to treat bladder spasms?

Mirabegron for Bladder Spasms

Mirabegron is indicated for overactive bladder (OAB) with symptoms of urge urinary incontinence, urgency, and urinary frequency, but is not specifically approved for general bladder spasms. 1 It is a beta-3 adrenergic agonist that works by relaxing the detrusor muscle during the storage phase of the urinary cycle.

Approved Indications

Mirabegron is FDA-approved for:

• Treatment of overactive bladder (OAB) in adults with symptoms of urge urinary incontinence, urgency, and urinary frequency
• Treatment of neurogenic detrusor overactivity (NDO) in pediatric patients aged 3 years and older weighing at least 35 kg 1

Mechanism and Efficacy

• Mirabegron works by activating beta-3 adrenergic receptors in the bladder, causing detrusor muscle relaxation during the filling phase
• It may also reduce activity in sensory nerves, helping to decrease urgency sensations 2
• Clinical trials have demonstrated significant improvements in:
  • Reduction in incontinence episodes
  • Decreased micturition frequency
  • Improved quality of life measures 3

Dosing Recommendations

• Starting dose: 25 mg orally once daily 4, 1
• After 4-8 weeks, may increase to 50 mg once daily if needed and tolerated 4, 1
• For adults, can be taken with or without food
• For pediatric patients, should be taken with food
• Tablets should be swallowed whole with water (not chewed, divided, or crushed) 1

Special Considerations

Dose Adjustments

• For severe renal impairment (eGFR 15-29 mL/min/1.73 m²), do not exceed 25 mg daily 4
• Not recommended in end-stage renal disease 1
• For moderate hepatic impairment, do not exceed 25 mg daily 1
• Not recommended in severe hepatic impairment 1

Contraindications

• Hypersensitivity to mirabegron or any inactive ingredients 1
• Severe uncontrolled hypertension 4, 1

Adverse Effects

• Most common adverse effects include:
  • Hypertension (requires monitoring)
  • Nasopharyngitis
  • Urinary tract infection
  • Headache 4, 1, 3
• Notably, mirabegron has a lower incidence of dry mouth (0.5-2.1%) compared to antimuscarinic agents, making it a better option for patients who cannot tolerate anticholinergic side effects 3, 5

Clinical Considerations for Bladder Spasms

• The American Urological Association recommends mirabegron as a preferred pharmacological option for elderly patients with OAB due to its better side effect profile, particularly regarding cognitive effects 4
• For patients who have failed anticholinergic therapy due to lack of efficacy or poor tolerability, mirabegron may be an effective alternative 2
• In patients with bladder outlet obstruction, mirabegron should be used with caution due to the risk of urinary retention 1
• Regular blood pressure monitoring is essential, especially in patients with pre-existing hypertension 4, 1

Combination Therapy

• For patients with inadequate response to monotherapy, the American Urological Association recommends mirabegron plus solifenacin 5mg, which has shown improved efficacy in clinical trials with a side effect profile similar to monotherapy 4

Important Precautions

• Monitor blood pressure regularly, especially in hypertensive patients
• Watch for signs of urinary retention in patients with bladder outlet obstruction
• Be aware of potential for angioedema (face, lips, tongue, larynx)
• Consider drug interactions with CYP2D6 substrates (e.g., thioridazine, flecainide, propafenone, digoxin) 1

While mirabegron is not specifically indicated for general bladder spasms, it is an effective treatment for overactive bladder symptoms, which often present as bladder spasms. Its favorable side effect profile makes it a good option, particularly for patients who cannot tolerate anticholinergic medications.