Skip to main content

β3-Adrenergic Receptor Agonists

β3-adrenergic receptor agonists are the contemporary companion class to antimuscarinics for overactive bladder (OAB) — working through the opposite arm of autonomic bladder physiology. Two agents are FDA-approved: mirabegron (Myrbetriq) and vibegron (Gemtesa). Both stimulate β3-adrenoceptors in the detrusor muscle to relax the detrusor during storage, increase functional bladder capacity, and reduce urgency — with efficacy comparable to antimuscarinics but a substantially better tolerability profile (no anticholinergic burden; this is not proof of zero long-term cognitive risk).[1][2][3]

The 2024 AUA/SUFU OAB guideline positions β3-agonists as first-line OAB pharmacotherapy alongside antimuscarinics, with a modest preference for β3-agonists in patients at risk for anticholinergic side effects.[4]

Mechanism of Action​

β3-adrenoceptors are highly expressed in the detrusor muscle. Stimulation activates adenylyl cyclase → cAMP production, producing:[2][3][5]

  • Direct detrusor smooth muscle relaxation during the storage phase
  • Decreased afferent signaling from the bladder
  • Improved bladder compliance during filling
  • Increased functional bladder capacity
  • Suppression of detrusor micro-contractions via effects on detrusor smooth muscle cells and suburothelial interstitial cells

Secondary mechanism — cholinergic inhibition​

Recent work has identified a prejunctional effect: β3 stimulation activates an EPAC1/PKC pathway that promotes adenosine release, providing additional cholinergic inhibition of parasympathetic nerves at the neuromuscular junction — a second, additive mechanism beyond direct smooth muscle relaxation.[6]

This multi-level mechanism helps explain why β3-agonists achieve efficacy comparable to antimuscarinics despite acting on a different receptor family.

FDA-Approved Agents​

Mirabegron (Myrbetriq)​

First-in-class — FDA-approved 2012.[7]

PropertyDetail
IndicationsOAB (adults); neurogenic detrusor overactivity in pediatric patients age ≥3 years
Adult dosingStart 25 mg PO daily; can increase to 50 mg after 4–8 weeks
Pediatric dosingWeight-based; granule or tablet formulations
Onset of efficacy4–8 weeks; sustained through 52 weeks
Key cautionsSevere uncontrolled HTN — not recommended; ESRD — not recommended; Child-Pugh C hepatic impairment — not recommended; lower dose ceiling with Child-Pugh B or eGFR 15–29
Drug interactionsCYP2D6 inhibitor — caution with metoprolol, desipramine, flecainide

Vibegron (Gemtesa)​

FDA-approved 2020 (OAB); 2024 expansion to OAB in men on BPH pharmacotherapy (COURAGE trial).[8][9]

PropertyDetail
IndicationsOAB (adults); OAB in adult males on BPH pharmacologic therapy (α-blocker ± 5-ARI)
Dose75 mg PO daily (no titration required)
Onset of efficacyWithin 4 weeks; sustained 52+ weeks
BP effectsMinimal — ambulatory BP monitoring shows no clinically meaningful changes[10]
Drug interactionsMinimal vs. mirabegron; no CYP2D6 concern

Clinical Efficacy​

Mirabegron — phase 3 data[1][7][11]​

OutcomeMirabegron 50 mgPlacebo
Micturition frequency reduction−1.6 to −1.9 episodes / 24 h−1.0 to −1.3
Incontinence reduction−1.4 to −1.6 episodes / 24 h−1.1 to −1.2
Volume per void+12 to +24 mL+7 to +12 mL

Network meta-analysis: mirabegron 50 mg has comparable overall efficacy to most antimuscarinics, with significantly better tolerability on dry mouth (better than 21/22 active comparators), constipation (9/20), and urinary retention (7/10).[12]

Vibegron — EMPOWUR trial (1,518 patients)[8][13]​

OutcomeVibegron 75 mgPlacebo
Micturition frequency reduction−1.8 episodes / 24 h−1.3
Incontinence reductionSignificantly greater than placebo (P<0.001)—
Volume per voidSignificantly greater increase (P<0.001)—
Durable effectSustained through 52 weeks—

Vibegron vs. mirabegron​

Head-to-head direct comparison is limited, but:

  • Indirect treatment comparison (Kennelly 2021): vibegron may have slightly greater efficacy for total incontinence episodes at 4 and 52 weeks and volume voided at 12 and 52 weeks[14]
  • 2025 network meta-analysis (Huang): vibegron outperformed mirabegron and antimuscarinics in reducing micturition frequency; vibegron 100 mg (dose higher than FDA-approved 75 mg) showed the greatest reduction[15]
  • Clinically, the two agents are largely interchangeable with a modest edge to vibegron on dosing simplicity (75 mg daily, no titration) and drug-interaction profile

Special Populations​

Men with BPH — the COURAGE trial​

Vibegron's 2024 FDA expansion for OAB in men on BPH therapy is backed by the COURAGE trial (1,105 men on α-blocker ± 5-ARI):[9]

Outcome at 12 weeksVibegron effect
Daily micturitions−0.74 (P<0.001)
Urgency episodesSignificantly reduced vs. placebo
IPSS-storage subscoreSignificantly improved vs. placebo
Retention / safetyComparable to placebo

This is the first β3-agonist approved specifically for the "prostate-with-OAB" phenotype — a common clinical scenario where antimuscarinics are often avoided due to retention concerns.

Elderly population​

  • Real-world data: β3-agonist recipients tend to be older (mean age 77.4 years for mirabegron vs. 69.2 for antimuscarinics)[16]
  • Reflects preference for β3-agonists in patients vulnerable to anticholinergic side effects
  • Avoiding anticholinergic burden is a practical advantage; observational comparisons do not prove absence of long-term dementia risk.

Pediatric NDO​

Mirabegron is FDA-approved for neurogenic detrusor overactivity in pediatric patients age ≥3 years — weight-based dosing with granule formulation.

Neurogenic LUT dysfunction​

Separate symptoms from urodynamic risk. EAU 2026 supports β3 agonists for neurogenic OAB symptoms, but recommends against using them specifically to reduce urodynamically proven NDO. Improvement in urgency does not establish renal protection; reassess pressure and compliance when these drive treatment.[22] Mirabegron's pediatric NDO indication does not confer an adult NDO indication; adult use for NDO is off-label. See NLUTD for risk-based surveillance.[7]

Adverse Effects​

Common[1][8][13][17]​

AEMirabegronVibegron
Hypertension8–9% (mild SBP ↑ 3–10 mm Hg at high doses)Minimal (ABPM: no clinically meaningful change)
UTI2–7%2–7%
Headache2–6%2–6%
Nasopharyngitis2–11%2–11%
Dry mouth1.7–2% (placebo-level; vs. 5% for antimuscarinics)Placebo-level
ConstipationLower than antimuscarinicsLower than antimuscarinics
Discontinuation for AELow1.7–2.4% (lower than tolterodine 3.3%)

Serious / unexpected adverse effects (pharmacovigilance)​

Post-marketing FDA FAERS data on mirabegron identified rare but flagged signals:[18]

  • Cardiac arrhythmias — atrial fibrillation, tachycardia, palpitations
  • Neurological events — reports of dementia, TIA, Parkinson's disease (signals; causality uncertain)
  • Vascular — ANCA-positive vasculitis (very rare)
  • Angioedema — lip / tongue swelling

Urinary retention​

Japanese JADER adverse event database analysis showed urinary retention as the most frequently reported AE:[19]

  • Mirabegron crude ROR: 62.1
  • Vibegron crude ROR: 250
  • Risk higher with: concomitant antimuscarinic, men with BPH, first 15 days of treatment

The COURAGE trial data in men on BPH therapy suggest this risk is manageable with appropriate selection — vibegron is now specifically approved for this population.

Cardiovascular safety​

Vibegron specifically: dedicated ambulatory BP monitoring studies demonstrate no clinically meaningful effects on BP or HR.[10][20] EMPOWUR: hypertension incidence with vibegron 1.7% vs. placebo 1.7%.

Mirabegron: small but detectable BP increases (SBP ↑ 3–10 mm Hg at doses 50–200 mg); monitor BP periodically.

Contraindications and Precautions​

Mirabegron[7]​

Not recommended for:

  • Severe uncontrolled hypertension
  • End-stage renal disease
  • Child-Pugh C hepatic impairment

The adult maximum is 25 mg/day with eGFR 15–29 or Child-Pugh B impairment. With CYP2D6 substrates (particularly narrow-therapeutic-index drugs such as flecainide), monitor and consider adjustment of the substrate drug; this is not a blanket contraindication to every CYP2D6 substrate.[7]

Vibegron​

  • No adjustment is recommended for eGFR 15–89 mL/min/1.73 m² or mild/moderate hepatic impairment. Not recommended with eGFR below 15 (including dialysis) or severe hepatic impairment.[23]
  • Digoxin requires level monitoring before and during coadministration, and after stopping vibegron; adjust digoxin as needed.[23]
  • Vibegron does not inhibit CYP2D6.[23]

General precautions​

  • BP monitoring — particularly for mirabegron, particularly in hypertensive patients
  • Urinary retention risk assessment — consider baseline PVR in men with BPH; particularly in the first 15 days of treatment
  • Concomitant antimuscarinic — increases retention risk

Combination Therapy​

Mirabegron 25–50 mg + solifenacin 5 mg provides superior efficacy vs. either agent alone for patients with suboptimal monotherapy response.[12][15][21] The trade-off: increased anticholinergic side effects (dry mouth, constipation) compared with β3-agonist monotherapy.

  • BESIDE and SYNERGY trials established efficacy of the combination
  • Stable option for patients whose OAB symptoms are not fully controlled on a single agent
  • Less-commonly used combinations (mirabegron + other antimuscarinics, vibegron + antimuscarinic) appear to have similar synergy based on mechanism

Clinical Positioning​

2024 AUA/SUFU framework[4]​

β3-agonists are positioned as:

  • First-line OAB pharmacotherapy alongside antimuscarinics
  • Preferred option for patients at risk for anticholinergic side effects:
    • Elderly
    • Cognitive impairment
    • Dry-mouth intolerance
    • Constipation-prone
    • Narrow-angle glaucoma
    • Men with BPH at risk for retention (vibegron FDA-approved for this population)
  • Alternative when antimuscarinics are contraindicated or not tolerated
  • Add-on therapy for patients with inadequate response to antimuscarinics

Other treatment options​

Discuss minimally invasive therapy when medication is ineffective, poorly tolerated or inconsistent with the patient’s preferences. The AUA/SUFU guideline permits these options through shared decision-making without requiring prior medication trials.[4] Options include:

  • Intradetrusor onabotulinumtoxinA (100 U idiopathic OAB; 200 U NLUTD)
  • Sacral neuromodulation (InterStim, Axonics)
  • Posterior tibial nerve stimulation (PTNS, eCoin, Revi)

See Also​

References​

1. Wei JT, Dauw CA, Brodsky CN. Lower urinary tract symptoms in men. JAMA. 2025;334(9):809–821. doi:10.1001/jama.2025.7045

2. Andersson KE, Martin N, Nitti V. Selective β3-adrenoceptor agonists for the treatment of overactive bladder. J Urol. 2013;190(4):1173–80. doi:10.1016/j.juro.2013.02.104

3. Igawa Y, Aizawa N, Michel MC. β3-adrenoceptors in the normal and diseased urinary bladder — what are the open questions? Br J Pharmacol. 2019;176(14):2525–2538. doi:10.1111/bph.14658

4. Cameron AP, Chung DE, Dielubanza EJ, et al. The AUA/SUFU guideline on the diagnosis and treatment of idiopathic overactive bladder. J Urol. 2024;212(1):11–20. doi:10.1097/JU.0000000000003985

5. Hennenberg M, Michel MC. Adrenoceptors in the lower urinary tract. Handb Exp Pharmacol. 2024;285:333–367. doi:10.1007/164_2023_678

6. Silva I, Magalhães-Cardoso MT, Ferreirinha F, et al. β adrenoceptor-induced cholinergic inhibition in human and rat urinary bladders involves the exchange protein directly activated by cyclic AMP 1 favoring adenosine release. Br J Pharmacol. 2020;177(7):1589–1608. doi:10.1111/bph.14921

7. Astellas Pharma US. Myrbetriq / Myrbetriq Granules (mirabegron): prescribing information. Sections 1.1–1.2. Manufacturer prescribing information; DailyMed label. Accessed September 11, 2026.

8. Staskin D, Frankel J, Varano S, et al. International phase III, randomized, double-blind, placebo and active controlled study to evaluate the safety and efficacy of vibegron in patients with symptoms of overactive bladder: EMPOWUR. J Urol. 2020;204(2):316–324. doi:10.1097/JU.0000000000000807

9. Staskin D, Owens-Grillo J, Thomas E, et al. Efficacy and safety of vibegron for persistent symptoms of overactive bladder in men being pharmacologically treated for benign prostatic hyperplasia: results from the phase 3 randomized controlled COURAGE trial. J Urol. 2024;212(2):256–266. doi:10.1097/JU.0000000000003999

10. Frankel J, Staskin D, Varano S, et al. An evaluation of the efficacy and safety of vibegron in the treatment of overactive bladder. Ther Clin Risk Manag. 2022;18:171–182. doi:10.2147/TCRM.S310371

11. Deeks ED. Mirabegron: a review in overactive bladder syndrome. Drugs. 2018;78(8):833–844. doi:10.1007/s40265-018-0924-4

12. Kelleher C, Hakimi Z, Zur R, et al. Efficacy and tolerability of mirabegron compared with antimuscarinic monotherapy or combination therapies for overactive bladder: a systematic review and network meta-analysis. Eur Urol. 2018;74(3):324–333. doi:10.1016/j.eururo.2018.03.020

13. Staskin D, Frankel J, Varano S, et al. Once-daily vibegron 75 mg for overactive bladder: long-term safety and efficacy from a double-blind extension study of the international phase 3 trial (EMPOWUR). J Urol. 2021;205(5):1421–1429. doi:10.1097/JU.0000000000001574

14. Kennelly MJ, Rhodes T, Girman CJ, et al. Efficacy of vibegron and mirabegron for overactive bladder: a systematic literature review and indirect treatment comparison. Adv Ther. 2021;38(11):5452–5464. doi:10.1007/s12325-021-01902-8

15. Huang W, Zheng X, Luo J, Chen Y, Xu Y. Comparative efficacy and adverse effects of β3-agonists and antimuscarinics in overactive bladder: a network and component network meta-analysis. Eur J Clin Pharmacol. 2025. doi:10.1007/s00228-025-03855-1

16. Huang CK, Lin CC, Lin AT. Effectiveness of antimuscarinics and a beta-3 adrenoceptor agonist in patients with overactive bladder in a real-world setting. Sci Rep. 2020;10(1):11355. doi:10.1038/s41598-020-68170-4

17. Chapple CR, Cruz F, Cardozo L, et al. Safety and efficacy of mirabegron: analysis of a large integrated clinical trial database of patients with overactive bladder receiving mirabegron, antimuscarinics, or placebo. Eur Urol. 2020;77(1):119–128. doi:10.1016/j.eururo.2019.09.024

18. Wang J, Zhang A, Ye M, Zhang C. Examining the safety of mirabegron: an analysis of real-world pharmacovigilance data from the US FDA Adverse Event Reporting System (FAERS) database. Front Pharmacol. 2024;15:1376535. doi:10.3389/fphar.2024.1376535

19. Kawazoe T, Ishida T, Jobu K, et al. Analysis of urinary retention caused by selective β3-adrenoceptor agonists using the Japanese Adverse Drug Event Report database (JADER). Pharmazie. 2023;78(5):56–62. doi:10.1691/ph.2023.3509

20. Peyronnet B, Brucker BM, De Nunzio C, et al. Vibegron in overactive bladder: a comprehensive review of efficacy, safety and patient-reported outcomes. World J Urol. 2025;43(1):514. doi:10.1007/s00345-025-05799-8

21. Jiang YH, Kuo HC. Current optimal pharmacologic therapies for overactive bladder. Expert Opin Pharmacother. 2023;24(18):2005–2019. doi:10.1080/14656566.2023.2264183

22. European Association of Urology. EAU Guidelines on Neuro-Urology. 2026. Section 3.4.2.d, drug treatment recommendations. Official guideline.

23. Sumitomo Pharma America, Inc. GEMTESA (vibegron): US prescribing information. Revised February 2025. Sections 7, 8.6, 8.7, and 12.3. Manufacturer label. Accessed September 11, 2026.