Mirabegron is a medicine that eases the symptoms of overactive bladder. It does not treat your condition.

It helps with symptoms such as:

• a sudden and urgent need to pee (urinary urgency)
• needing to pee more often than usual (urinary frequency)
• wetting yourself if you cannot make it to the loo in time (urinary incontinence)

Mirabegron works by relaxing the muscles around your bladder. This means your bladder can hold more liquid and reduces your need to pee as often or as urgently.

This medicine is only available on prescription.

It comes as slow-release tablets (called "modified release" or "prolonged release"). This means the tablets release mirabegron slowly and evenly throughout the day.

• You'll usually take mirabegron once a day.
• Common side effects include urine infections and a fast heartbeat.
• Your doctor may recommend mirabegron if other medicines for overactive bladder have not helped.
• You will usually take this medicine long-term to help keep your symptoms under control.
• Mirabegron starts to work within a few hours but it can take several weeks to reach its full effect.

Mirabegron can be taken by adults (aged 18 years and over).

It is not suitable for everyone. To make sure it's safe for you, tell your doctor or pharmacist before starting mirabegron if you:

• have had an allergic reaction to mirabegron or any other medicines in the past
• have liver or kidney problems
• have high blood pressure
• are not able to pee or empty your bladder completely (urinary retention)
• have a blockage in your bladder
• have a heart problem called QT prolongation
• are pregnant, trying to get pregnant or breastfeeding

You'll usually take mirabegron once a day. It does not matter what time you take this medicine as long as it is at the same time each day.

Swallow the tablets whole with a drink of water. Do not chew or crush them.

You can take mirabegron with or without food.

How much will I take?

Mirabegron comes as 25mg and 50mg tablets.

The usual dose is 50mg, taken once a day.

If you have a kidney or liver problem, your doctor may recommend a lower dose of 25mg taken once a day.

What if I forget to take it?

If you forget to take your medicine, take it as soon as you remember unless the next dose is due in less than 6 hours. In this case skip the missed dose and take your next one at the usual time.

Do not take a double dose to make up for a missed dose.

If you forget doses often, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

If you take too much mirabegron, it is unlikely to harm you.

If you take an extra dose by mistake, you might get some of the common side effects, such as increased heart rate, or headache and dizziness.

Like all medicines, mirabegron can cause side effects in some people, but many people have no side effects or only minor ones.

Side effects often improve as your body gets used to the medicine.

Common side effects

Common side effects happen in more than 1 in 100 people. They are usually mild and shortlived.

Talk to your doctor or pharmacist if the side effects bother you or do not go away:

• feeling sick (nausea)
• constipation
• diarrhoea
• urinary tract infection (UTI) – pain or a burning sensation when peeing; smelly or cloudy pee
• headache
• feeling dizzy
• fast heart rate – you can feel your heart beating faster than usual for no obvious reason (like vigorous exercise)

Serious side effects

Serious side effects are rare and happen in less than 1 in 1,000 people.

What to do about:

• feeling sick – try taking mirabegron with a meal or snack. It may also help if you stick to simple meals and avoid rich or spicy food.
• constipation – eat more high-fibre foods such as fresh fruit, vegetables and cereals, and drink plenty of water. Try to exercise more regularly, for example, by going for a daily walk or run. If this does not help, talk to your pharmacist or doctor. Watch this short video about how to treat constipation.
• diarrhoea – drink lots of fluids, such as water or squash, to avoid dehydration. Signs of dehydration include peeing less than usual or having dark strong-smelling pee. Do not take any other medicines to treat diarrhoea without speaking to a pharmacist or doctor.
• urinary tract infection (UTI) – if you think you have a UTI, ask a pharmacist or doctor to recommend a treatment. Tell them that you are taking mirabegron.
• headache – make sure you rest and drink plenty of fluids. Do not drink too much alcohol. Ask a pharmacist to recommend a painkiller. Talk to your doctor if the headaches continue or are severe.
• feeling dizzy – stop what you're doing and sit or lie down until you feel better. Do not drive, ride a bike or operate machinery until it passes. If you are still having dizzy spells after a week, speak to your doctor.
• fast heart rate – lie down and try to relax. This is usually nothing to worry about and will pass. Contact 111 if your heart beat does not slow down after resting, or if you have chest pain.

Mirabegron is not usually recommended in pregnancy. There's not enough information available to say whether it's safe or not to take this medicine during pregnancy.

There may be other medicines for treating urinary symptoms that are safer for you.

If you're pregnant or trying to get pregnant, talk to your doctor about the benefits and possible risks of taking mirabegron.

Mirabegron and breastfeeding

There's not a lot of information about the safety of mirabegron when breastfeeding.

Mirabegron is likely to pass into your breast milk and so it may cause problems for your baby.

Talk to your doctor, as other medicines for urinary symptoms might be better while you're breastfeeding.

Mirabegron may affect the way other medicines work, and other medicines may affect how mirabegron works.

Tell your pharmacist or doctor if you're taking:

• digoxin, a medicine for heart failure or abnormal heart rhythm
• imipramine or desipramine, medicines for urinary incontinence or nerve pain
• dabigatran, a blood thinner (anticoagulant)
• clarithromycin, an antibiotic
• ketoconazole or itraconazole, medicines used to treat fungal infections
• ritonavir, a medicine used to treat HIV

Taking mirabegron with herbal remedies and supplements

There's very little information about taking mirabegron with herbal remedies and supplements. These remedies are not tested in the same way as medicines.