The most common side effect of Myrbetriq (mirabegron) is a rise in blood pressure, affecting about 9% of people taking the standard 50 mg dose. Other frequent side effects include urinary tract infections (6%), headache (4%), common cold symptoms (4%), and, at lower rates, back pain, constipation, and dry mouth (about 3% each). Most of these are mild and may ease as your body adjusts to the medication.
The Most Common Side Effects by Frequency
Data from TAURUS, a 12-month clinical trial of over 800 people taking Myrbetriq 50 mg, gives a clear picture of what to expect:
- High blood pressure: 9.2%
- Urinary tract infection: 5.9%
- Headache: 4.1%
- Nasopharyngitis (cold-like symptoms): 3.9%
- Back pain: 2.8%
- Constipation: 2.8%
- Dry mouth: 2.8%
Pooled data from three other large clinical trials found no clear dose-response pattern, meaning the 25 mg starting dose and the 50 mg maintenance dose produced similar overall rates of side effects. Some side effects fade on their own during the first weeks of treatment as your body adjusts.
Why Blood Pressure Is the Top Concern
Myrbetriq works by activating a specific type of receptor (beta-3 adrenergic) on the bladder muscle, causing it to relax. About 97% of the adrenergic receptors in the bladder are this subtype, which is why the drug targets the bladder so effectively. But a small amount of stimulation reaches other parts of the body too, and there appears to be a dose-dependent increase in both heart rate and blood pressure.
In practical terms, the average blood pressure increase measured across three 12-week trials was modest: roughly 0.5 to 1 mmHg above placebo for both systolic and diastolic readings. That’s barely noticeable for most people. But for the subset who already have elevated blood pressure, even a small nudge matters. The FDA recommends against using Myrbetriq if your blood pressure is severely uncontrolled, defined as systolic at or above 180 mmHg or diastolic at or above 110 mmHg.
If you’re already being treated for high blood pressure, periodic monitoring makes sense after starting Myrbetriq. Your blood pressure numbers won’t spike dramatically in most cases, but the trend is worth watching over time.
How Myrbetriq Compares to Older Bladder Medications
Before Myrbetriq, the main medications for overactive bladder were anticholinergics like oxybutynin, tolterodine, and solifenacin. These drugs are effective, but they’re notorious for drying out your mouth and causing constipation. Myrbetriq works through a completely different mechanism, and that shows up clearly in the side effect comparisons.
Dry mouth occurred in 3.4% of people taking Myrbetriq 50 mg compared to 6.3% with solifenacin and 11.7% with tolterodine. That’s roughly half to one-third the rate. Constipation, on the other hand, was similar across all three drugs at about 2%. Rates of dizziness, serious adverse events, and heart rhythm problems were also comparable between Myrbetriq and the older options in both short-term (8 to 12 week) and long-term (52 week) studies.
So the practical advantage of Myrbetriq isn’t that it’s free of side effects. It’s that the side effects are different. If dry mouth was the reason you stopped an older bladder medication, Myrbetriq is significantly less likely to cause that particular problem. But it introduces the blood pressure concern that anticholinergics don’t carry.
Rare but Serious Reactions
In fewer than 1% of patients, Myrbetriq can trigger a hypersensitivity reaction or angioedema. Angioedema is swelling beneath the skin, most commonly in the lips, tongue, face, or throat. It typically develops over hours and can last up to three days. Because throat swelling can obstruct your airway, this is a medical emergency. If you notice sudden swelling of your face, lips, or throat after starting Myrbetriq, seek immediate medical attention.
These reactions are uncommon enough that most people will never experience them, but they are serious enough to be worth knowing about before you start the medication.
Interactions With Other Medications
Myrbetriq slows down one of the liver enzymes (CYP2D6) that breaks down certain other medications. This means those drugs can build up to higher levels in your bloodstream than expected. The FDA prescribing information specifically flags metoprolol (a common blood pressure medication), desipramine (an antidepressant), and several heart rhythm drugs including flecainide and propafenone.
If you take any of these, your prescriber may need to adjust doses or monitor you more closely. This interaction is worth mentioning at the pharmacy, especially since metoprolol is one of the most widely prescribed blood pressure medications and many people with overactive bladder are in the age group that also takes it.
What the Long-Term Safety Data Shows
Myrbetriq has been on the market since 2012, giving regulators over a decade of real-world safety data. A 2025 FDA review of all serious adverse event reports found no new safety signals beyond what was already known from clinical trials, no increase in the severity of known side effects, and no deaths directly attributed to the drug in pediatric patients. While that review focused on patients under 18, it reflects the broader pattern: Myrbetriq’s safety profile has remained stable since approval.
For most adults, the side effects are manageable and predictable. Blood pressure is the one to actively track, especially in the first few months. The other common side effects, including headache, mild cold symptoms, and occasional urinary tract infections, are the kind that tend to resolve on their own or are easy to treat when they arise.