Mirabegron Zentiva: Uses, Dosage & Side Effects

What Is Mirabegron Zentiva and What Is It Used For?

Mirabegron Zentiva contains the active substance mirabegron, which belongs to a pharmacological class known as beta-3 adrenergic receptor agonists. It is the first medication in this class to be approved for the treatment of overactive bladder (OAB), representing a genuinely novel therapeutic approach to a condition that affects hundreds of millions of people worldwide. The medication is manufactured by Zentiva as a generic equivalent to the originator brand Betmiga (known as Myrbetriq in the United States and some other markets).

Overactive bladder is a clinical syndrome defined by the International Continence Society (ICS) as the presence of urinary urgency, usually accompanied by increased daytime frequency and nocturia (waking at night to urinate), with or without urge urinary incontinence, in the absence of urinary tract infection or other obvious pathology. OAB affects an estimated 12–17% of the adult population in developed countries, with prevalence increasing significantly with age. Both men and women are affected, though the pattern of symptoms may differ: women are more likely to experience urge incontinence, while men more commonly report urgency and frequency without incontinence. The condition has a profound impact on quality of life, affecting sleep, work productivity, sexual function, and psychological well-being, and is associated with increased rates of depression, anxiety, and social isolation.

The pathophysiology of OAB involves involuntary contractions of the detrusor muscle (the smooth muscle layer of the bladder wall) during the storage phase of the micturition cycle, when the bladder should normally be relaxing to accommodate increasing volumes of urine. In a healthy bladder, the storage phase is dominated by sympathetic nervous system activity, which promotes detrusor relaxation through activation of beta-adrenergic receptors. Research has shown that beta-3 adrenoceptors are the predominant beta-adrenergic receptor subtype in the human detrusor muscle, accounting for approximately 97% of beta-adrenoceptor messenger RNA in the bladder. Activation of these beta-3 receptors stimulates the cyclic adenosine monophosphate (cAMP) signaling pathway, leading to smooth muscle relaxation.

Mirabegron selectively activates beta-3 adrenoceptors on the detrusor smooth muscle. By stimulating these receptors, mirabegron promotes bladder relaxation during the filling phase without affecting the voiding contraction. This is a critical distinction from anticholinergic (antimuscarinic) medications, which work by blocking muscarinic receptors on the detrusor muscle. While anticholinergics have been the mainstay of OAB pharmacotherapy for decades, their mechanism of action inevitably leads to blockade of muscarinic receptors elsewhere in the body, causing well-known side effects including dry mouth, constipation, blurred vision, tachycardia, and — of particular concern in the elderly — cognitive impairment and increased risk of dementia with long-term use.

The clinical efficacy of mirabegron has been established in a comprehensive phase III clinical trial program. The three pivotal studies — SCORPIO, ARIES, and CAPRICORN — enrolled over 4,600 patients with OAB symptoms and demonstrated statistically significant and clinically meaningful improvements in the key OAB endpoints:

• SCORPIO (Europe/Australia): A 12-week randomized, double-blind, placebo- and active-controlled (tolterodine 4 mg) trial in 1,978 patients. Mirabegron 50 mg significantly reduced the mean number of micturitions per 24 hours (primary endpoint) by −1.75 versus −1.34 for placebo (p < 0.05). Incontinence episodes were reduced by −1.57 versus −1.17 for placebo (p < 0.05). The results were comparable to tolterodine 4 mg but with a significantly lower incidence of dry mouth.
• ARIES (North America): A 12-week randomized, double-blind, placebo-controlled trial in 1,328 patients. Mirabegron 50 mg significantly reduced micturitions (−1.66 versus −1.05 for placebo, p < 0.001) and incontinence episodes (−1.47 versus −1.13 for placebo, p < 0.05).
• CAPRICORN (Europe/North America/Australia): A 12-week randomized, double-blind, placebo-controlled trial in 1,306 patients. Mirabegron 50 mg significantly reduced micturitions (−1.55 versus −1.18 for placebo, p < 0.05) and urgency episodes.

Long-term efficacy and safety data from a 12-month extension study (TAURUS) involving 2,452 patients confirmed that the improvements in OAB symptoms observed at 12 weeks were maintained over 12 months of continuous treatment. The study also compared mirabegron 50 mg with tolterodine extended-release 4 mg, finding comparable efficacy but a significantly lower rate of dry mouth with mirabegron (2.8% versus 8.6%).

Mirabegron was first approved by the Japan Pharmaceutical and Food Safety Bureau in 2011, followed by the U.S. FDA in 2012 and the European Medicines Agency (EMA) in 2012. It is now approved in more than 60 countries worldwide and has been included in major international clinical guidelines as a first-line pharmacological option for OAB, including guidelines from the European Association of Urology (EAU), the American Urological Association (AUA), and the International Continence Society (ICS).

What Should You Know Before Taking Mirabegron Zentiva?

Contraindications

Mirabegron Zentiva must not be used in certain clinical situations. The absolute contraindications are conditions where the risks of treatment clearly outweigh any potential benefit. You must not take this medication if you have a known hypersensitivity (allergy) to mirabegron or to any of the excipients listed in the composition section of this article. Allergic reactions to mirabegron, although uncommon, have been reported and can include skin rash, pruritus (itching), urticaria (hives), and in rare cases, angioedema (swelling of the face, lips, tongue, or throat) and anaphylactic reactions.

Mirabegron is also contraindicated in patients with severe uncontrolled hypertension, defined as systolic blood pressure of 180 mmHg or greater and/or diastolic blood pressure of 110 mmHg or greater. This is because mirabegron can cause small increases in blood pressure through its adrenergic activity, and administering it to patients whose blood pressure is already dangerously elevated could increase the risk of hypertensive emergencies, stroke, or other cardiovascular events. Before starting treatment, your doctor should measure your blood pressure to ensure it is adequately controlled.

Additionally, mirabegron is contraindicated in patients with end-stage renal disease (estimated glomerular filtration rate below 15 mL/min/1.73 m² or patients requiring hemodialysis) and in patients with severe hepatic impairment (Child-Pugh Class C). In both of these conditions, the metabolism and excretion of mirabegron are significantly impaired, leading to substantially higher plasma concentrations that could increase the risk of adverse effects.

Warnings and Precautions

Several important warnings and precautions should be discussed with your healthcare provider before and during treatment with Mirabegron Zentiva:

• Hypertension: In clinical trials, mirabegron 50 mg was associated with average increases of approximately 0.5–1.0 mmHg in systolic blood pressure and 0.5 mmHg in diastolic blood pressure compared with placebo. While these average increases are small, individual responses may vary. Patients with pre-existing hypertension (even if controlled) should have their blood pressure monitored at baseline and at regular intervals during treatment. If blood pressure increases significantly, your doctor may need to adjust your antihypertensive medications or discontinue mirabegron.
• Urinary tract infection: Urinary tract infections (UTIs) were one of the most commonly reported adverse events in clinical trials. If you develop symptoms suggestive of a UTI (such as pain or burning during urination, cloudy or strong-smelling urine, or fever), consult your doctor promptly for evaluation and treatment.
• Urinary retention: Although mirabegron works by relaxing the bladder during the filling phase rather than suppressing the voiding contraction, cases of urinary retention have been reported in post-marketing surveillance, particularly in patients with bladder outlet obstruction (such as men with benign prostatic hyperplasia) and in patients concurrently taking anticholinergic medications for OAB. If you experience difficulty urinating or feel that your bladder is not emptying completely, contact your doctor immediately.
• Hepatic impairment: In patients with mild hepatic impairment (Child-Pugh Class A), no dose adjustment is required. For patients with moderate hepatic impairment (Child-Pugh Class B), the dose should not exceed 25 mg once daily (where available). Mirabegron is contraindicated in severe hepatic impairment (Child-Pugh Class C).
• Renal impairment: No dose adjustment is required for patients with mild to moderate renal impairment. For patients with severe renal impairment (eGFR 15–29 mL/min/1.73 m²), the dose should not exceed 25 mg once daily (where available). Mirabegron is contraindicated in end-stage renal disease.

Pregnancy and Breastfeeding

If you are pregnant, think you may be pregnant, or are planning to become pregnant, consult your doctor before using Mirabegron Zentiva. There are limited data on the use of mirabegron in pregnant women. Animal reproductive studies have shown adverse effects on fetal development at doses significantly higher than the therapeutic dose in humans, including delayed ossification and reduced fetal weight in rats and rabbits at maternally toxic doses. The relevance of these findings to humans is uncertain, but as a precaution, mirabegron should not be used during pregnancy unless the potential benefit clearly justifies the potential risk to the fetus. Women of childbearing potential should use effective contraception during treatment.

It is not known whether mirabegron or its metabolites are excreted in human breast milk. Studies in rats have shown that mirabegron and its metabolites are present in the milk of lactating rats. A risk to the breastfed infant cannot be excluded. The decision to continue or discontinue breastfeeding or to continue or discontinue mirabegron therapy should take into account the benefit of breastfeeding for the child and the benefit of treatment for the mother. Consult your doctor for guidance on this decision.

Driving and Operating Machinery

Mirabegron Zentiva has no or negligible influence on the ability to drive or operate machinery based on its pharmacological properties and the adverse effect profile observed in clinical trials. Dizziness has been reported as an uncommon side effect; if you experience dizziness while taking this medication, you should avoid driving or operating machinery until the symptom resolves.

Children and Adolescents

The safety and efficacy of mirabegron have been studied in pediatric patients aged 3 to 17 years with neurogenic detrusor overactivity. However, the results of these studies were not sufficient to support a general pediatric indication. Mirabegron Zentiva is not approved for use in children and adolescents, and treatment decisions in pediatric patients should be made by a specialist in pediatric urology.

How Does Mirabegron Zentiva Interact with Other Drugs?

Unlike many medications used in urology, mirabegron has a clinically relevant drug interaction profile that requires careful consideration. Mirabegron is metabolized by multiple pathways including cytochrome P450 3A4 (CYP3A4), CYP2D6, butyrylcholinesterase (BChE), uridine diphosphate-glucuronosyltransferases (UGT), and direct amide hydrolysis. More importantly, mirabegron is a moderate inhibitor of the CYP2D6 enzyme and an inhibitor of the P-glycoprotein (P-gp) efflux transporter, which means it can affect the plasma concentrations of other medications that are substrates of these systems.

The inhibition of CYP2D6 by mirabegron is of particular clinical significance because many commonly prescribed medications are metabolized by this enzyme. In pharmacokinetic studies, co-administration of mirabegron 160 mg (a supratherapeutic dose used to assess the maximum inhibitory effect) with metoprolol, a CYP2D6 substrate, increased metoprolol exposure (AUC) by approximately 3.3-fold. At the therapeutic dose of 50 mg, the increase in metoprolol exposure is expected to be approximately 1.8-fold, which may be clinically relevant for drugs with a narrow therapeutic index.

The inhibition of P-glycoprotein by mirabegron can increase the absorption and decrease the elimination of P-gp substrate drugs. In a pharmacokinetic study, co-administration of mirabegron with digoxin (a P-gp substrate with a narrow therapeutic index) increased digoxin exposure (AUC) by approximately 27% and peak concentration (Cmax) by approximately 29%. When initiating mirabegron in patients already taking digoxin, the lowest dose of digoxin should be used initially, and serum digoxin concentrations should be monitored.

As a general principle, caution is recommended when mirabegron is co-administered with drugs that have a narrow therapeutic index and are primarily metabolized by CYP2D6. Examples include certain antiarrhythmics (flecainide, propafenone), tricyclic antidepressants (desipramine, imipramine, nortriptyline), neuroleptics (thioridazine, haloperidol), and some beta-blockers (metoprolol, timolol). For these drugs, dose adjustments may be necessary, and patients should be monitored for signs of increased drug exposure.

Additionally, patients taking medications that affect the QT interval should be managed with particular care, as increased plasma levels of QT-prolonging drugs due to CYP2D6 inhibition by mirabegron could theoretically increase the risk of cardiac arrhythmias. Although mirabegron itself has not been shown to prolong the QT interval at therapeutic doses (a thorough QT/QTc study showed no clinically relevant effect), the interaction with CYP2D6-dependent drugs warrants caution.

What Is the Correct Dosage of Mirabegron Zentiva?

Mirabegron Zentiva should always be taken exactly as your doctor has prescribed. The medication is formulated as a prolonged-release (extended-release) tablet designed to release the active substance gradually over time, providing consistent drug levels throughout the day with once-daily dosing. It is critical that the tablet is swallowed whole with a glass of water or other liquid and is not crushed, chewed, or divided, as this would destroy the prolonged-release mechanism and could result in an excessive release of mirabegron, potentially causing increased adverse effects.

Adults

The recommended starting and maintenance dose for adults with overactive bladder is 50 mg once daily. Unlike many OAB medications that require dose titration (starting at a lower dose and gradually increasing), mirabegron 50 mg can be initiated directly without an up-titration phase, which simplifies the treatment process for both patients and healthcare providers. This is because the 50 mg dose provides the optimal balance of efficacy and tolerability based on the extensive clinical trial data.

Mirabegron Zentiva can be taken at any time of day, with or without food. Food does not significantly affect the overall absorption (AUC) of mirabegron, although it may slightly reduce the peak plasma concentration (Cmax) and delay the time to peak concentration (Tmax). These changes are not clinically significant and do not require any dose adjustment. Many patients find it helpful to take the medication at the same time each day to establish a consistent routine.

Elderly Patients

No dose adjustment is required for elderly patients based on age alone. In clinical trials, approximately 50% of treated patients were aged 65 years or older, and approximately 12% were aged 75 years or older. The efficacy and safety profile of mirabegron in elderly patients was consistent with the overall study population. This is particularly relevant because OAB is most prevalent in older adults, and mirabegron’s lack of anticholinergic side effects makes it an especially attractive option in this age group, where anticholinergic medications have been associated with cognitive decline and increased risk of falls. However, elderly patients should still have their blood pressure monitored regularly, and renal and hepatic function should be assessed to determine if dose adjustments are warranted.

Missed Dose

If you forget to take a dose of Mirabegron Zentiva, take it as soon as you remember on the same day. However, if it is almost time for your next scheduled dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a forgotten dose. The prolonged-release formulation and the relatively long half-life of mirabegron (approximately 50 hours) mean that missing a single dose is unlikely to result in a significant loss of therapeutic effect, but consistent daily dosing is recommended for optimal symptom control.

Overdose

Single doses of mirabegron up to 400 mg have been studied in healthy volunteers (8 times the recommended therapeutic dose). At these supratherapeutic doses, the most commonly observed effects were increased heart rate and increased blood pressure. In the event of an overdose, symptomatic and supportive care is recommended, with monitoring of heart rate, blood pressure, and electrocardiogram (ECG). Due to the high protein binding of mirabegron (approximately 71%) and its large volume of distribution, hemodialysis is not expected to be effective in removing the drug from the body.

What Are the Side Effects of Mirabegron Zentiva?

Like all medicines, Mirabegron Zentiva can cause side effects, although not everybody gets them. The overall safety profile of mirabegron is well characterized through an extensive clinical development program involving over 10,000 patients treated with the drug, as well as post-marketing surveillance data from its worldwide use since 2011. The most notable aspect of mirabegron’s safety profile is the absence of anticholinergic side effects, which distinguishes it from the traditional antimuscarinic medications used for overactive bladder.

In the pooled clinical trial data at the recommended 50 mg dose, the most frequently reported adverse reactions were urinary tract infection (3.0% versus 2.6% for placebo), tachycardia (1.6% versus 1.0% for placebo), and nasopharyngitis (common cold; 3.4% versus 3.1% for placebo). The incidence of dry mouth, the most problematic side effect of anticholinergic OAB medications, was notably low with mirabegron (1.7% versus 1.4% for placebo at 50 mg, compared with 8.6% for tolterodine 4 mg in the comparative TAURUS study).

The following side effects have been reported in clinical trials and post-marketing experience with mirabegron, organized by frequency:

The cardiovascular effects of mirabegron merit particular discussion. The small increases in heart rate (average 1–2 beats per minute) and blood pressure observed in clinical trials are consistent with the drug’s pharmacological mechanism as a beta-3 adrenergic agonist. While beta-3 receptors predominate in the bladder, beta-1 and beta-2 receptors are present in the cardiovascular system, and some degree of cross-reactivity at therapeutic doses cannot be completely excluded. A thorough QT/QTc study at supratherapeutic doses (100 mg and 200 mg) did not show clinically relevant QT prolongation. However, patients with a history of cardiac arrhythmias or significant cardiovascular disease should be monitored more closely.

Long-term safety data from the 12-month TAURUS study and subsequent post-marketing surveillance have been reassuring, with no new safety signals emerging with prolonged use. The incidence of adverse events did not increase over time, and the overall discontinuation rate due to adverse events was low (approximately 5–6% in clinical trials, comparable to placebo).

How Should You Store Mirabegron Zentiva?

Proper storage of medication is essential to ensure that it remains effective and safe throughout its shelf life. Mirabegron Zentiva should be stored at room temperature, not exceeding 25°C (77°F). There are no special temperature requirements such as refrigeration, making this medication straightforward to store in most home environments. However, avoid storing the medication in locations subject to excessive heat, such as near radiators, in direct sunlight, or in a car during warm weather.

The tablets should be kept in their original packaging (blister pack or bottle, as applicable) to protect them from moisture. The prolonged-release coating of the tablet is sensitive to humidity, and exposure to moisture could compromise the controlled-release mechanism, potentially affecting both the efficacy and safety of the medication. Do not transfer the tablets to a different container unless that container provides equivalent moisture protection.

Keep this medicine out of the sight and reach of children. Accidental ingestion of mirabegron by children could cause adverse effects, particularly increased heart rate and blood pressure. If you suspect a child has accidentally swallowed this medication, contact your local poison control center or seek emergency medical attention immediately.

Do not use Mirabegron Zentiva after the expiry date stated on the packaging (EXP). The expiry date refers to the last day of that month. Do not throw away any medicines via wastewater or household waste. Return unused or expired medication to your local pharmacy for safe disposal in accordance with local regulations. This helps to protect the environment and prevent accidental exposure to others.

What Does Mirabegron Zentiva Contain?

Mirabegron Zentiva 50 mg prolonged-release tablets contain mirabegron as the sole active pharmaceutical ingredient. Mirabegron (chemical name: 2-(2-amino-1,3-thiazol-4-yl)-N-[4-(2-{[(2R)-2-hydroxy-2-phenylethyl]amino}ethyl)phenyl]acetamide) is a synthetic compound with a molecular formula of C₂₁H₂₄N₄O₂S and a molecular weight of 396.51 g/mol. It is a white to off-white crystalline powder that is practically insoluble in water.

The prolonged-release formulation uses a matrix tablet technology in which the active substance is embedded within a polymer matrix that controls the rate of drug release. As the tablet passes through the gastrointestinal tract, the outer layers of the matrix gradually hydrate and swell, forming a gel layer that slowly releases mirabegron over an extended period. This prolonged-release mechanism ensures relatively stable plasma concentrations over the 24-hour dosing interval, reducing the peak-to-trough fluctuation and contributing to consistent symptom control throughout the day and night.

The inactive ingredients (excipients) in Mirabegron Zentiva 50 mg prolonged-release tablets typically include pharmaceutical-grade components necessary for the prolonged-release matrix system and film coating. These may include macrogol, hydroxypropyl cellulose, butylhydroxytoluene (BHT), magnesium stearate, and components of the film coating such as hypromellose, macrogol, iron oxide yellow (E172), and iron oxide red (E172), which give the tablet its characteristic appearance. The exact excipient composition may vary slightly between manufacturers and markets; always refer to the patient information leaflet included with your specific medication for the complete list of ingredients.

If you have known allergies or intolerances to any pharmaceutical excipients, review the full list of ingredients with your pharmacist before starting treatment. The medication does not contain lactose, gluten, or significant amounts of sodium, making it suitable for most patients with common dietary sensitivities.