Myrbetriq side effects and how to avoid them

Myrbetriq side effects | Serious side effects | High blood pressure | Urinary retention | Angioedema | How long do side effects last? | Warnings | Interactions | How to avoid side effects | Resources

Myrbetriq is a brand-name prescription drug that treats overactive bladder (OAB) in adults and pediatric neurogenic detrusor overactivity (NDO) in children ages 3 years and older. The active ingredient in Myrbetriq is mirabegron, a beta-3 adrenergic agonist that works by relaxing the bladder muscle responsible for pushing urine out of the bladder. Relaxing this muscle increases the bladder’s capacity to store urine. Mirabegron does not affect the bladder muscle’s ability to void urine during the voiding phase. As with all prescription drugs, it helps to know what side effects to expect when taking Myrbetriq, as well as potential drug interactions and warning signs for problems when taking this drug. 

RELATED: What is Myrbetriq?

Common side effects of Myrbetriq

The most common adverse reactions to Mybetriq are:

• Elevated blood pressure
• Urinary tract infection (UTI)/Cystitis
• Headache
• Stuffy nose and sore throat (nasopharyngitis)
• Upper respiratory tract infection (URI)
• Joint pain/back pain
• Constipation
• Dry mouth
• Dizziness 
• Racing heartbeats (tachycardia)
• Palpitations
• Nausea (in children)
• Gastroenteritis (in children)
• Runny, stuffy nose, and cough (in children)

Some side effects, like dry mouth, urinary tract infection, constipation, and fast heartbeat, are more likely to be experienced when Myrbetriq is taken daily in combination with VESIcare (solifenacin succinate).

Serious side effects of Myrbetriq

The most severe side effects of Myrbetriq include:

• High blood pressure (hypertension)
• Urinary retention
• Hallucinations 
• Severe allergic reactions including angioedema

Myrbetriq and high blood pressure

Myrbetriq can raise blood pressure in both adults and children, affecting anywhere from 7.5% to 24% of people taking Myrbetriq. In most cases, this rise in blood pressure may be minor. In clinical studies, the average rise in blood pressure was 4 mm/Hg systolic and 1.6 mm/Hg diastolic. Even a slight rise in blood pressure may be a problem in people diagnosed with hypertension. Although Myrbetriq increases blood pressure, most studies have found it to have no effect on eye pressure, so it is generally considered safe for patients with glaucoma. 

Myrbetriq and urinary retention

Myrbetriq relaxes the muscle responsible for squeezing urine out of the bladder, so some people taking Myrbetriq have experienced urinary retention, a potentially serious side effect in which people lose the ability to fully empty the contents of their bladder. Although the exact incidence is unknown, urinary retention as a side effect of Myrbetriq is largely limited to either people with bladder outlet obstruction, or people taking overactive bladder medications belonging to a family of drugs called muscarinic receptor antagonists (MRAs), such as oxybutynin or VESIcare (solifenacin succinate).

Myrbetriq and angioedema

Although the incidence is not known, some people taking Myrbetriq have experienced angioedema, a severe and potentially life-threatening hypersensitivity reaction involving swelling of the face, mouth, and throat. Any allergic reaction to Myrbetriq requires emergency medical attention. Angioedema will require the immediate discontinuation of Myrbetriq. People with a history of angioedema may not be able to take this medicine.

How long do side effects last?

The terminal half-life of mirabegron is 50 hours, that is, it takes 50 hours for the body to eliminate half a dose from the body. Most common side effects such as headache, increased blood pressure, constipation, pain, and dry mouth should feel better in a few days, or a few weeks.

Infections may take longer to get better and require medical treatment even if the medicine is discontinued. Severe allergic reactions may require several days of medical treatment to improve.

Myrbetriq contraindications & warnings

All prescription drugs have some risks, particularly for people with certain pre-existing physical conditions. Myrbetriq is no exception. Some people may not be able to take Myrbetriq, while others may need to watch more carefully for side effects or other problems when taking this medicine. 

Abuse and dependence

Myrbetriq is not a drug subject to abuse, nor do patients taking Myrbetriq develop physical or psychological dependence on the drug. Discontinuing Myrbetriq will not cause withdrawal symptoms.

Overdose

Taking too much Myrbetriq can cause the heart to beat faster and cause palpitations. Elevated blood pressure is also a concern. Call a poison helpline or get emergency medical treatment if an overdose of Myrbetriq is suspected.

Restrictions

Not everyone can safely take Myrbetriq. People who have an allergic reaction to mirabegron or any of the inactive ingredients in Myrbetriq will not be able to take this medicine. Other contraindications include people with severe and uncontrolled high blood pressure or anyone with severe kidney disease. Because the drug is broken down by the liver, people with severe liver disease will probably not be given Myrbetriq, either.

People with some conditions may need dosage adjustments or monitoring because of pre-existing conditions. Both the kidneys and liver eliminate mirabegron from the body, so people with moderate kidney disease or moderate liver disease will have a lower maximum dose than other people. Because of the risk for urinary retention, people with bladder obstruction will require close monitoring when taking Myrbetriq.

Pregnancy and breastfeeding

There is not enough information about Myrbetriq’s effects on pregnancy or unborn babies to determine if it is safe to take during pregnancy. Women who are pregnant or considering pregnancy should consult with their healthcare provider.

There are also no studies about the presence of mirabegron in breast milk or its effects on a nursing baby. Because of the lack of information, healthcare professionals will suggest breastfeeding mothers use an alternative OAB drug whose safety profile is better known. 

Children

The U.S. Food and Drug Administration (FDA) has approved Myrbetriq for use in children as young as 3 years of age to treat pediatric neurogenic detrusor overactivity (NDO), a bladder dysfunction related to nerve disease or injury. Children and adolescents should take Myrbetriq with food.

Older adults

Myrbetriq is prescribed to older adults at recommended doses. Clinical studies have shown no difference in the safety and effectiveness of Myrbetriq in people of advanced age compared to younger adults.

Myrbetriq interactions

As with all prescription drugs, some adverse effects of taking Myrbetriq are due to drug interactions. To avoid these problems, keep a current list of all the prescription drugs, over-the-counter drugs, dietary supplements, and herbal remedies that are being taken, and always share that list when getting prescriptions. Myrbetriq’s most significant drug interactions include

• Contraindicated drugs: some drugs are never combined with Myrbetriq, that is, they are “contraindicated.” For Myrbetriq, both the antipsychotic medication thioridazine and the highly specialized drug Cedelga (eliglustat) are never to be taken along with Myrbetriq.
• Monoamine oxidase inhibitors: healthcare professionals don’t know if it’s safe to combine Myrbetriq with monoamine oxidase inhibitors (MAOIs), a small family of drugs. MAOIs are not safe to take with a wide variety of other drugs, so healthcare providers will avoid prescribing them with Myrbetriq.
• Bladder-specific antimuscarinics: also called muscarinic receptor antagonists (MRAs), some antimuscarinics also relax bladder muscles and are very commonly used to treat urinary incontinence. While Myrbetriq is sometimes combined with an MRA, the combination raises the risk of urinary retention.

Mirabegron blocks the ability of a liver enzyme, called CYP2D6, to metabolize other substances, including drugs. Many different types of drugs are metabolized by this enzyme, so they are not broken down efficiently by the body when combined with mirabegron. As a result, these drugs last in the body at high concentrations for a longer time, raising the risks of side effects. If these drugs are combined with Myrbetriq, their dosages may need to be reduced. The most significant of these drugs include

• Antidepressants
• Opioids
• Antipsychotic medications
• Beta blockers (such as metoprolol)
• Heart rhythm drugs 

How to avoid Myrbetriq side effects

While side effects are possible when taking Myrbetriq, they can be prevented or minimized. Always talk to a healthcare provider about side effects and any tips they have to prevent side effects. Keep in mind, however, that one key strategy for managing side effects is to maximize the benefits of taking the medicine. Taking the medicine properly will provide the most profitable trade-off between the good things the medicine does versus the bad things.

1. Take Myrbetriq as directed

The first defense against side effects is to take Myrbetriq exactly as a healthcare professional has directed. Make sure to read and follow the instructions in the drug information sheet or the patient information sheet. 

• Do not take more or less than indicated on the prescription label. 
• Take all doses as scheduled. If a dose is missed, take the missed dose as soon as possible. However, if it’s been 12 hours or more since the dose was supposed to be taken, skip it and take the next dose as scheduled. 
• Always swallow the Myrbetriq extended-release tablet whole. Do not chew it, break it, or crush it.
• Make sure that Myrbetriq is properly stored at room temperature. 
• Remember: Myrbetriq Granules expire 28 days after the pharmacist prepares the oral suspension. Stop using the medicine after those 28 days have passed.

2. Tell the prescribing healthcare provider about all medical conditions

Many adverse effects are caused by underlying physical conditions. It always helps to make sure that the prescribing healthcare provider has a complete medical history. When prescribing Myrbetriq, they should particularly be informed about:

• Liver problems
• Kidney problems
• Uncontrolled and severe high blood pressure
• Difficulty emptying the bladder or a weak stream during urination
• Any history of hereditary angioedema
• Pregnancy or any pregnancy plans
• Breastfeeding or plans to breastfeed

3. Tell the healthcare provider about all medications being taken

Drug interactions are another major source of adverse effects in people taking Myrbetriq. Make sure the prescribing healthcare professional knows about all drugs and supplements being taken, especially:

• The antipsychotic medication thioridazine
• The heart/heart rhythm drugs flecainide, Lanoxin (digoxin), and Rythmol (propafenone)
• The anticoagulant warfarin
• The urinary incontinence medication VESIcare (solifenacin succinate)

4. Watch for signs of an allergic reaction

One of Myrbetriq’s most severe side effects is angioedema, an allergic reaction that causes swelling of the face, mouth, and throat. Angioedema could be life-threatening if the airways swell shut. When taking Myrbetriq, get emergency medical attention if you have symptoms of an allergic reaction such as hives, rash, itching, chest tightness, trouble breathing, blistering, or swelling.

5. Monitor blood pressure

Myrbetriq can raise blood pressure. It usually isn’t that much, but it could vary from person to person. Consider purchasing a blood pressure cuff and taking blood pressure readings regularly, particularly if high blood pressure is already a problem. Tell the prescribing healthcare provider about any rise in blood pressure while taking Myrbetriq. 

6. Drink plenty of fluids 

Drink enough fluids to help prevent side effects such as headache, constipation, and dry mouth.

7. Add a fiber supplement 

If constipation is a problem, eat high fiber foods or add a fiber supplement.

Resources

• Adrenergic drugs, StatPearls
• Mirabegron—a selective beta3-adrenoreceptor agonist for the treatment of overactive bladder, Research and Reports in Urology
• Mirabegron drug summary, Prescriber’s Digital Reference
• Myrbetriq, Epocrates
• Myrbetriq prescribing information, U.S. National Library of Medicine
• Pharmacotherapy for pediatric neurogenic detrusor overactivity, Pediatric Drugs