Mirabegron

Overactive Bladder

Mirabegron is primarily used to treat adults who have symptoms of an overactive bladder (OAB). It helps manage the following conditions:

• Urge urinary incontinence: A sudden, strong need to urinate that leads to the involuntary leaking of urine.
• Urinary urgency: An immediate and intense need to urinate.
• Urinary frequency: Needing to urinate more often than is typical.

Neurogenic Detrusor Overactivity

This medication is also used in children to treat neurogenic detrusor overactivity (NDO). This is a bladder control problem related to neurological conditions, such as spina bifida or spinal cord injury. In these cases, the medication helps the bladder muscle relax while it is filling, which increases the amount of urine the bladder can hold and reduces leaking.

How Mirabegron Works

Mirabegron belongs to a class of medications called beta-3 adrenergic agonists. It works by targeting specific receptors found in the detrusor muscle, which is the muscle that makes up the wall of the bladder.

In a healthy bladder, the detrusor muscle relaxes to allow the bladder to fill with urine and contracts when it is time to urinate. For those with an overactive bladder, this muscle may contract involuntarily, causing a sudden and frequent need to go. Mirabegron helps manage these symptoms through the following actions:

• Relaxing the bladder: The medication activates beta-3 receptors, which signals the bladder muscle to stay relaxed while it is storing urine.
• Improving capacity: When the muscle is relaxed, the bladder can expand more effectively, allowing it to hold a larger volume of urine.
• Controlling urgency: By preventing the bladder muscle from contracting too early or unexpectedly, the medication reduces the frequency of bathroom visits and the sudden, intense urge to urinate.

Common Side Effects

Many people using mirabegron experience mild side effects. These may include:

• Increased blood pressure
• Headache
• Dry mouth
• Constipation or diarrhea
• Dizziness
• Back or joint pain
• Cold-like symptoms, such as a sore throat, runny nose, or sinus pain
• Urinary tract infection

Serious Side Effects

While less common, some side effects require immediate medical attention. Contact a healthcare provider right away if you experience:

• Severe high blood pressure: Symptoms may include a severe headache, blurred vision, or a pounding sensation in the neck or ears.
• Urinary retention: Difficulty urinating, a weak urine stream, or the inability to empty your bladder.
• Allergic reactions: Swelling of the face, lips, tongue, or throat (angioedema), itching, or hives.
• Heart rhythm changes: A fast, pounding, or irregular heartbeat.

Blood Pressure Monitoring

Mirabegron can increase blood pressure. It is generally recommended that blood pressure be checked before starting treatment and monitored periodically while taking the medication. This drug is not recommended for individuals with severe, uncontrolled high blood pressure.

Urinary Retention

There is a risk of urinary retention, which is the inability to empty the bladder completely. This risk may be higher for individuals with a bladder outlet obstruction or those who are also taking anticholinergic medications for overactive bladder.

Allergic Reactions

Serious allergic reactions, including angioedema, have been reported. This involves swelling of the face, lips, tongue, or throat, which can make breathing difficult. If these symptoms occur, medical attention is typically required immediately.

Kidney and Liver Function

The kidneys and liver help remove mirabegron from the body. Individuals with severe kidney disease or moderate to severe liver disease may require a lower dose or may be advised to avoid the medication entirely. It is generally not recommended for people with end-stage renal disease or severe liver impairment.

Drug Interactions

Mirabegron can affect how the body processes other medications, particularly those metabolized by a specific enzyme called CYP2D6. This may increase the levels of certain heart medications or antidepressants in the blood, potentially increasing the risk of side effects from those drugs.

Pregnancy

There is limited information regarding the safety of using mirabegron during pregnancy. It is currently unknown whether this medication can cause harm to an unborn baby. Healthcare providers typically only prescribe mirabegron to pregnant individuals if the potential benefits to the patient outweigh the potential risks to the fetus.

If you are pregnant or planning to become pregnant, discuss the risks and benefits of this treatment with your doctor. If you become pregnant while taking this medication, notify your healthcare provider immediately.

Breastfeeding

It is not known if mirabegron passes into human breast milk or how it might affect a nursing infant. Because the risks are unclear, it is important to talk with a healthcare professional before breastfeeding while using this medication. They can help determine the best course of action for both the parent and the child.

Available Forms

Mirabegron is available in oral formulations designed for slow release. These include:

• Extended-release tablets
• Extended-release granules (for oral suspension)

The granules are typically mixed with water before administration. Both forms are designed to provide a steady level of medication in the system.

FDA Approval and Indications

Mirabegron received its initial FDA approval in 2012. It is approved for use in adults to treat overactive bladder (OAB) with symptoms of urge urinary incontinence, urgency, and urinary frequency. It may be used alone or in combination with the drug solifenacin succinate for this purpose.

The FDA has also approved mirabegron for the treatment of neurogenic detrusor overactivity (NDO) in pediatric patients 3 years of age and older.

Regulatory Warnings and Precautions

While mirabegron does not carry a boxed warning, the FDA-approved labeling includes specific precautions regarding blood pressure. The medication can increase blood pressure, and it is recommended that healthcare providers measure blood pressure before starting treatment and monitor it periodically. It is not recommended for patients with severe, uncontrolled hypertension.

The FDA labeling also contains information regarding pharmacogenomics. Mirabegron is a moderate inhibitor of CYP2D6, an enzyme involved in drug metabolism. This regulatory information is provided to help clinicians manage potential drug interactions with other medications metabolized by this same pathway.

Factors Influencing Cost

The price you pay for mirabegron can vary based on several factors:

• Generic Availability: Mirabegron is available as a generic medication and as the brand-name drug Myrbetriq. Generic versions are generally more affordable than brand-name products.
• Insurance and Medicare: Many insurance plans and Medicare Part D programs cover mirabegron. The out-of-pocket cost will depend on your plan's specific tier for the drug and your remaining deductible.
• Pharmacy Selection: Retail prices for the same prescription can differ between pharmacies. Some patients may find lower costs through mail-order pharmacy services.
• Assistance Programs: Some manufacturers offer savings cards or patient assistance programs for those who qualify, which can help lower the cost for eligible patients.

To determine the exact cost, it is best to contact your insurance provider or local pharmacist for a price quote based on your specific prescription.