Understanding Overactive Bladder (OAB)
Overactive bladder is a condition characterized by a group of urinary symptoms, including a sudden and uncontrollable urge to urinate (urgency), frequent urination, and nighttime urination (nocturia) [1.6.1]. It is not a disease but a symptom complex that can significantly impact a person's quality of life, affecting work, social activities, and sleep [1.6.1]. The condition results from miscommunication between the brain and the bladder, causing the bladder muscles to contract involuntarily even when the bladder is not full [1.6.3]. While OAB affects both men and women, with overall prevalence being similar, symptom expression can differ [1.6.4]. An estimated 30% of men and 40% of women in the U.S. live with OAB symptoms [1.6.1].
What is Myrbetriq (mirabegron)?
Myrbetriq, with the active ingredient mirabegron, is a prescription medication approved for the treatment of OAB in adults and neurogenic detrusor overactivity (NDO) in children [1.2.3, 1.3.3]. It belongs to a class of drugs called beta-3 adrenergic agonists [1.2.2].
Mechanism of Action: Myrbetriq works differently from older OAB medications. It activates beta-3 adrenergic receptors in the bladder's detrusor muscle. This activation helps the bladder muscle to relax and increase its capacity to store urine, thereby reducing OAB symptoms [1.2.2, 1.3.8].
Dosage and Administration: For adults, the typical starting dose is a 25 mg extended-release tablet taken once daily. This may be increased to 50 mg once daily after 4 to 8 weeks, depending on efficacy and patient tolerance [1.3.4, 1.3.5]. The medication can be taken with or without food [1.3.5].
Efficacy and Side Effects: Clinical studies show Myrbetriq is effective at reducing urinary frequency and incontinence episodes [1.2.4]. A significant advantage is its side effect profile. Because it is not an anticholinergic, it has a much lower risk of causing dry mouth and constipation compared to medications like Toviaz [1.5.2]. The most common side effects associated with Myrbetriq include increased blood pressure, urinary tract infections (UTIs), and headaches [1.2.2, 1.2.3]. Regular blood pressure monitoring is recommended, especially for patients with hypertension [1.7.6].
What is Toviaz (fesoterodine)?
Toviaz, with the active ingredient fesoterodine fumarate, is another prescription medication used to treat OAB in adults and NDO in children [1.4.4, 1.4.5]. It belongs to a class of drugs known as anticholinergics (or antimuscarinics) [1.2.4].
Mechanism of Action: Toviaz works by blocking muscarinic receptors in the bladder. This action prevents the neurotransmitter acetylcholine from causing involuntary contractions of the bladder muscle, thus reducing bladder muscle spasms, decreasing the sense of urgency, and improving bladder control [1.2.4, 1.4.2].
Dosage and Administration: The recommended starting dose for adults is 4 mg once daily. Based on the individual's response and tolerability, the dose can be increased to the maximum of 8 mg once daily [1.4.1, 1.4.4].
Efficacy and Side Effects: Toviaz is also proven to be effective in managing OAB symptoms [1.2.4]. Some studies suggest that the 8 mg dose of fesoterodine may be more efficacious than mirabegron 50 mg for certain endpoints like reducing urgency urinary incontinence [1.5.2]. However, its use is often limited by its side effects, which are characteristic of the anticholinergic class. The most prevalent side effects are dry mouth and constipation [1.2.2, 1.2.3]. Other potential side effects include dizziness, drowsiness, and blurred vision [1.7.2]. Due to these effects, it should be used with caution in elderly patients and those with certain conditions like narrow-angle glaucoma or myasthenia gravis [1.2.3].
Head-to-Head Comparison: Myrbetriq vs. Toviaz
The choice between Myrbetriq and Toviaz often comes down to a balance between efficacy, side effect tolerability, and the patient's overall health profile.
| Feature | Myrbetriq (mirabegron) | Toviaz (fesoterodine) |
|---|---|---|
| Drug Class | Beta-3 Adrenergic Agonist [1.2.2] | Anticholinergic / Antimuscarinic [1.2.2] |
| Mechanism | Relaxes the bladder muscle to increase its storage capacity [1.3.8]. | Blocks nerve signals (acetylcholine) that cause bladder muscle spasms [1.2.4]. |
| Efficacy | Both are considered effective for OAB symptoms [1.2.4]. Some studies show similar efficacy, while others suggest fesoterodine 8mg may have an edge in some metrics [1.5.2, 1.5.3]. | Both are considered effective for OAB symptoms [1.2.4]. Some studies show similar efficacy, while others suggest fesoterodine 8mg may have an edge in some metrics [1.5.2, 1.5.3]. |
| Common Side Effects | Increased blood pressure, headaches, urinary tract infections [1.2.2]. | Dry mouth (very common), constipation, blurred vision, dizziness [1.2.3, 1.7.2]. |
| Key Advantage | Lower incidence of anticholinergic side effects like dry mouth and constipation [1.5.2]. | May be more effective in certain patient populations or at higher doses [1.5.2, 1.5.4]. |
| Key Disadvantage | Can increase blood pressure; requires monitoring [1.7.6]. | High rate of bothersome side effects (dry mouth, constipation) that can lead to discontinuation [1.7.2]. Potential for cognitive side effects. |
| Cost | Brand-name only in some forms, though a generic has been approved [1.2.3]. Without insurance, can be expensive, around $457 for 30 tablets [1.2.3]. | Available as a lower-cost generic [1.2.3]. Brand name can cost around $291-$473 without insurance [1.2.3, 1.4.3]. |
| Drug Interactions | Interacts with certain drugs like digoxin and some anticholinergics [1.7.3]. | Interacts with many medications, particularly other anticholinergics and strong CYP3A4 inhibitors like ketoconazole [1.2.3, 1.4.1]. |
Conclusion: Which One is Right for You?
Deciding whether Myrbetriq or Toviaz is better is a decision that must be made in consultation with a healthcare provider. Both medications are effective treatments for overactive bladder, but they are not interchangeable.
Myrbetriq is often favored for patients who cannot tolerate the classic anticholinergic side effects of dry mouth and constipation, or for those at risk for cognitive side effects associated with anticholinergics [1.5.5]. However, it is not suitable for individuals with severe, uncontrolled hypertension [1.7.6].
Toviaz may be a suitable option and is available in a more affordable generic form [1.2.3]. Its efficacy, especially at the 8mg dose, is well-established [1.5.2]. The choice may depend on whether a patient can tolerate the common side effects. The decision ultimately hinges on an individual's specific symptoms, co-existing medical conditions, tolerance for potential side effects, and insurance coverage.
For more information on overactive bladder, you can visit the Urology Care Foundation.
