Mirabegron (Myrbetriq)
Astellas Pharma 2012 FDA-approved selective β3-adrenoceptor agonist (Myrbetriq), originally an overactive bladder (OAB) Rx. Since Cypess 2015 BAT-activation trial, used off-label as a thermogenic fat-loss tool: +5-10% BMR with active brown adipose tissue volume.
DETAILED OVERVIEW
What is Mirabegron (Myrbetriq)?
Mirabegron (Myrbetriq) is a first-in-class selective β3-adrenoceptor agonist developed by Astellas Pharma and FDA-approved in 2012 for symptomatic treatment of overactive bladder (OAB). The β3-receptor's specific tissue expression drives its clinical relevance: in detrusor smooth muscle it mediates bladder relaxation (clinical OAB indication), while in brown adipose tissue (BAT) it triggers UCP1-mediated thermogenic activation that enables its off-label fat-loss use. Cypess 2015 Cell Metabolism PMID 25437872 was the first human trial to demonstrate significant BAT activation following a single oral 200 mg dose in healthy adults (PET-CT 18F-FDG measurement). Loh 2019 PMID 31263458 and Finlin 2020 J Clin Invest PMID 32119651 further validated chronic-dose metabolic rate elevation + visceral adipose tissue browning-induction. Clinical OAB dosing is 25-50 mg/day; off-label fat-loss protocols typically use 75-100 mg/day. The FDA's 2018 black-box update warns pre-existing cardiovascular-disease patients after post-marketing severe hypertension + tachycardia case clusters. WADA does not list it as explicitly banned, but several national federations classify it as monitored.
Mechanism
Selective β3-adrenoceptor agonist (detrusor + BAT UCP1 induction)
Dosing
Clinical OAB 25-50 mg/day; off-label fat-loss 75-100 mg/day PO AM
Half-life
~50 hours (once-daily dosing optimal)
Onset time
Detrusor 2-4 h; BAT activation chronic dose 2-4 weeks
Legal status
FDA + EMA Rx (OAB), HU + PL registered. WADA: not explicitly banned, monitored by some national federations.
Mirabegron stands out in community reports as one of the few compounds with actual human evidence for brown adipose tissue (BAT) activation. Users describe it as well tolerated, with a real but mild "background" thermogenic effect that passively contributes to fat loss – notably without any stimulant-like feeling. Reports consistently frame it as a long-game compound rather than a rapid weight-shedding tool.
At higher doses, a noticeable rise in resting heart rate or blood pressure is reported, which is why some accounts mention co-administration with a selective beta-1 blocker; the more pronounced fat-loss effects also tend to appear only at those higher doses. Combining it with cold-exposure protocols is anecdotally said to amplify BAT activation, as both target similar thermogenic pathways.
⚠ Not clinical evidence – based on user accounts.
Data console
Lab data
Hadi FA, Schild A, Hansen MK . Efficacy and Safety of Mirabegron in Males with Overactive Bladder and Lower Urinary Tract Symptoms: Analysis from an Integrated Clinical Trial Database.. Eur Urol Open Sci.
Cypess AM, Weiner LS, Roberts-Toler C, Franquet Elía E, Kessler SH, Kahn PA, English J, Chatman K, Trauger SA, Doria A, Kolodny GM . Activation of human brown adipose tissue by a β3-adrenergic receptor agonist.. Cell Metab.
Loh RKC, Formosa MF, La Gerche A, Reutens AT, Kingwell BA, Carey AL . Acute metabolic and cardiovascular effects of mirabegron in healthy individuals.. Diabetes Obes Metab.
O'Mara AE, Johnson JW, Linderman JD, Brychta RJ, McGehee S, Fletcher LA, Fink YA, Kapuria D, Cassimatis TM, Kelsey N, Cero C, Sater ZA, Piccinini F, Baskin AS, Leitner BP, Cai H, Millo CM, Dieckmann W, Walter M, Javitt NB, Rotman Y, Walter PJ, Ader M, Bergman RN, Herscovitch P, Chen KY, Cypess AM . Chronic mirabegron treatment increases human brown fat, HDL cholesterol, and insulin sensitivity.. J Clin Invest.
Cypess AM, White AP, Vernochet C et al. . Anatomical localization, gene expression profiling and functional characterization of adult human neck brown fat. Nat Med. 2013;19(5):635-639..
White WB, Siddiqui E, Tat T, Franks B, Schermer CR . Cardiovascular safety of mirabegron: analysis of an integrated clinical trial database of patients with overactive bladder syndrome.. J Am Soc Hypertens.
Safety
Side effects, stop signs, contraindications
Side effects · 8
- Blood pressure elevation, hypertension (dose-dependent, one of the most common and clinically important effects; pre-existing hypertension can worsen)
- Tachycardia, increased resting heart rate, palpitations
- Urinary retention, difficulty voiding, urinary tract infection (from detrusor relaxation, especially with bladder outlet obstruction)
- Headache, dizziness
- Nasopharyngitis, upper respiratory symptoms, dry mouth
- Constipation, nausea, abdominal discomfort
- QTc prolongation at higher doses (ECG monitoring warranted, especially with other QT-prolonging drugs)
- Rare but serious: angioedema (swelling of face, lips, tongue, larynx, with airway-obstruction risk – requires immediate discontinuation)
Contraindications · 7
- Severe, uncontrolled hypertension (>=180/110 mmHg) – absolute contraindication (FDA warning; do not start if blood pressure is uncontrolled)
- Severe renal impairment (ESRD/dialysis) and severe hepatic impairment (Child-Pugh C) – not recommended; dose reduction required in moderate impairment
- Clinically significant bladder outlet obstruction or OAB treated with antimuscarinics – increased urinary retention risk
- Pre-existing tachyarrhythmia, unstable/significant cardiac disease, or known QT prolongation / QT-prolonging drugs – elevated cardiac risk
- Pregnancy and breastfeeding – not recommended (insufficient human safety data)
- Hypersensitivity to mirabegron or excipients, or prior history of angioedema
- Caution with sensitive CYP2D6 substrates (e.g. metoprolol, desipramine) and CYP2D6-inhibiting SSRIs/TCAs – plasma-level increase, dose adjustment may be needed
Related Performance Compounds
Same therapeutic category
Studies
Related research and clinical findings
Efficacy and Safety of Mirabegron in Males with Overactive Bladder and Lower Urinary Tract Symptoms: Analysis from an Integrated Clinical Trial Database.
Hadi FA, Schild A, Hansen MK
Activation of human brown adipose tissue by a β3-adrenergic receptor agonist.
Cypess AM, Weiner LS, Roberts-Toler C, Franquet Elía E, Kessler SH, Kahn PA, English J, Chatman K, Trauger SA, Doria A, Kolodny GM
Acute metabolic and cardiovascular effects of mirabegron in healthy individuals.
Loh RKC, Formosa MF, La Gerche A, Reutens AT, Kingwell BA, Carey AL
Chronic mirabegron treatment increases human brown fat, HDL cholesterol, and insulin sensitivity.
O'Mara AE, Johnson JW, Linderman JD, Brychta RJ, McGehee S, Fletcher LA, Fink YA, Kapuria D, Cassimatis TM, Kelsey N, Cero C, Sater ZA, Piccinini F, Baskin AS, Leitner BP, Cai H, Millo CM, Dieckmann W, Walter M, Javitt NB, Rotman Y, Walter PJ, Ader M, Bergman RN, Herscovitch P, Chen KY, Cypess AM
Anatomical localization, gene expression profiling and functional characterization of adult human neck brown fat
Cypess AM, White AP, Vernochet C et al.
Cardiovascular safety of mirabegron: analysis of an integrated clinical trial database of patients with overactive bladder syndrome.
White WB, Siddiqui E, Tat T, Franks B, Schermer CR
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The information here is for educational and scientific purposes only. Performance-enhancing compounds (AAS, prohormones, stimulants, doping agents) are illegal without prescription in Hungary and most of the EU, and carry serious health and legal risks. WADA bans them in competitive sport. This is NOT a usage guide, and we do not encourage any illegal use. If you do use them, medical supervision and regular bloodwork are ESSENTIAL. Severe endocrine, cardiovascular, hepatic and psychiatric side effects are possible.