Myrbetriq (Mirabegron) and Dizziness/Sleepiness
Myrbetriq can cause dizziness but does not typically cause sleepiness. Dizziness is a documented adverse effect occurring in approximately 2.7% of patients, while somnolence (sleepiness) is not listed among the common side effects in clinical trials 1.
Dizziness Profile
According to FDA labeling data, dizziness was reported in:
- 2.7% of patients taking Myrbetriq 50 mg in long-term studies (compared to 2.6% on active control) 1
- Listed among adverse reactions occurring in less than 1% of patients in 12-week trials 1
- Reported as a reason for treatment discontinuation in 0.5% of patients 1
In pediatric populations with neurogenic detrusor overactivity, dizziness was noted as an adverse effect in real-world use 1, 2.
Sleepiness/Somnolence Profile
Sleepiness is NOT a characteristic side effect of mirabegron. The FDA label specifically lists "somnolence" under nervous system disorders but only in the context of general postmarketing reports, not as a common adverse event from clinical trials 1. In fact, a large registry study (PERSPECTIVE) documented that when nervous system disorders occurred, they included headache, somnolence, and dizziness—but these were grouped together and were not prominent findings 3.
Most Common Adverse Effects
The actual common side effects you should counsel patients about are 1:
- Hypertension (7.5-11.3%)
- Nasopharyngitis (3.5-3.9%)
- Urinary tract infection (2.9-4.2%)
- Headache (2.1-3.2%)
- Constipation (1.6%)
- Dry mouth (2.8% in long-term studies)
Clinical Implications
If a patient reports significant sleepiness on Myrbetriq, investigate alternative causes including:
- Concomitant medications (particularly if combined with antimuscarinics, which can cause drowsiness)
- Underlying medical conditions
- Sleep disorders
- Other CNS-active medications
The 2023 EAU guidelines confirm that mirabegron is "well tolerated in the elderly and in patients with multiple comorbidities" with the most frequent adverse events being hypertension, UTIs, headache, and nasopharyngitis—not sedation 4.
Bottom line: Warn patients about possible dizziness (occurs in ~3% of patients), but sleepiness is not an expected side effect of Myrbetriq monotherapy. If drowsiness occurs, look elsewhere for the cause.