Myrbetriq Side Effects: What to Expect and When to Call Your Doctor

Myrbetriq (mirabegron) is generally well-tolerated compared to older overactive bladder medications. But like any prescription drug, it has a side effect profile worth understanding before you start. Here's a plain-language breakdown of what to expect, organized by severity.

Why Myrbetriq Has a Different Side Effect Profile Than Other OAB Drugs

Most OAB drugs are anticholinergics — they work by blocking acetylcholine receptors throughout the body. This is effective for the bladder but also causes dry mouth, constipation, blurred vision, urinary retention, and in older adults, can contribute to cognitive problems. Myrbetriq works differently: it's a beta-3 adrenergic agonist, stimulating beta-3 receptors in the bladder muscle directly. This targeted mechanism means fewer anticholinergic side effects — but introduces its own set of considerations.

Common Myrbetriq Side Effects (Occur in More Than 2% of Patients)

These are the most frequently reported side effects from clinical trials. Most are mild and manageable:

• High blood pressure (hypertension): The most significant common side effect. Myrbetriq can raise systolic and diastolic blood pressure by a small amount (approximately 0.5-1 mm Hg on average in OAB adults). Monitor your blood pressure, especially in the first few weeks.
• Nasopharyngitis: Cold-like symptoms (runny nose, sore throat). Commonly reported but usually mild and temporary.
• Urinary tract infection (UTI): Reported in about 4% of patients in clinical trials. Symptoms include burning with urination, frequent urination, and cloudy urine. Contact your doctor if you suspect a UTI.
• Headache: Some patients report headaches, especially when first starting. Usually resolves over time.
• Constipation: Less common than with anticholinergic OAB drugs but still reported. Increase water and fiber intake if this occurs.
• Tachycardia (rapid heartbeat): Some patients experience a mildly elevated heart rate. If you notice persistent palpitations or a racing heart, contact your doctor.
• Dry mouth: More common when Myrbetriq is taken in combination with solifenacin (Vesicare). Reported in up to 9.3% of patients on combination therapy.

Post-Marketing (Real-World) Side Effects

After Myrbetriq was on the market, additional side effects were reported outside of clinical trials. These don't necessarily occur in most patients but have been seen:

• Atrial fibrillation (irregular heart rhythm)
• Nausea
• Diarrhea
• Dizziness

Serious Side Effects: Call Your Doctor or Seek Emergency Care

While rare, these serious side effects require immediate medical attention:

• Angioedema (swelling of the face, lips, tongue, or throat): Has been reported with Myrbetriq, sometimes after the very first dose. Call 911 immediately if you experience throat or tongue swelling, as this can be life-threatening. Stop taking Myrbetriq.
• Severe or uncontrolled high blood pressure: Myrbetriq is not recommended in patients with a systolic blood pressure ≥180 mm Hg or diastolic ≥110 mm Hg. If you check your blood pressure and get a reading in this range, contact your doctor immediately.
• Urinary retention: Difficulty emptying the bladder completely. More likely in patients with bladder outlet obstruction or those also taking anticholinergic OAB drugs. Seek care if you cannot urinate.
• Atrial fibrillation: Symptoms include a racing, fluttering, or irregular heartbeat. Seek emergency care if you experience these symptoms with chest pain or shortness of breath.

Who Should NOT Take Myrbetriq?

Myrbetriq is contraindicated only in patients with a known allergy to mirabegron or any inactive ingredient in the tablet. However, extra caution is needed for:

• Patients with severe uncontrolled hypertension (SBP ≥180 or DBP ≥110 mm Hg) — Myrbetriq is not recommended
• Patients with bladder outlet obstruction — urinary retention risk
• Patients on CYP2D6 substrates with narrow therapeutic index — dose adjustment may be needed

Tips for Minimizing Side Effects

• Take Myrbetriq at the same time each day for consistent blood levels
• Monitor your blood pressure weekly for the first month, especially if you have hypertension
• Stay well-hydrated to reduce risk of UTI and constipation
• Swallow the tablet whole — do not crush, chew, or divide it

For more, see Myrbetriq Drug Interactions and What Is Myrbetriq?.