How does it work?
Betmiga prolonged-release tablets contain the active ingredient mirabegron, which is a type of medicine called a selective beta3 adrenoceptor agonist. It is used to treat the symptoms of an overactive bladder (OAB).
The muscle in the wall of the bladder is called the detrusor muscle. It can sometimes contract in uncontrollable spasms, and this is often referred to as having an overactive bladder. The overactive detrusor muscle can increase in the number of times you need to pass urine, or cause uncontrollable urges to pass urine, or involuntary leakage of urine (urinary incontinence).
Mirabegron works in a different way to the standard antimuscarinic treatments for an overactive bladder. It relaxes the detrusor muscle in the wall of the bladder by stimulating the beta 3 receptors that are found on the surface of the muscle cells. This relaxation of the bladder muscle helps to increase the capacity of the bladder to hold urine. In turn, this reduces the need to pass urine.
Betmiga tablets are prolonged-release tablets that release the medicine gradually over the day. This type of tablet must be swallowed whole, not broken, crushed or chewed, as this would damage the prolonged-release action.
What is it used for?
- Reducing the increased need to pass urine (urinary frequency), uncontrollable urges to pass urine (urinary urgency) and involuntary leakage of urine (urinary incontinence) in people with an overactive bladder.
How do I take it?
- The usual dose is one 50mg Betmiga tablet taken regularly once a day. Try to always take your tablet at the same time of day.
- Betmiga tablets should be swallowed whole with a drink. They can be taken either with or without food. The tablets should not be chewed, broken or crushed.
- If you forget to take a dose at your usual time, take it as soon as you remember. However, if it is less than six hours until your next dose is due just leave out the forgotten dose. Do not take a double dose to make up for a missed dose.
- You should not stop taking this medicine if you do not notice an improvement in your symptoms straightaway. It may take some time for your bladder to adapt and your symptoms to improve. You should continue with the tablets and only stop taking them if you have discussed it with your doctor, because if you stop treatment your overactive bladder symptoms may come back.
Use with caution in
- People with mild to moderately decreased kidney function.
- People with mild to moderately decreased liver function.
- People with high blood pressure.
- People with a personal or family history of an abnormal heart rhythm, see on an ECG as a 'prolonged QT interval'.
- People taking medicines that can cause a 'prolonged QT interval' (see end of page for examples).
Not to be used in
- People with uncontrolled high blood pressure.
- People with severely decreased liver function.
- People with end stage kidney disease or who are having haemodialysis for kidney failure.
- People with moderately decreased liver function or severely decreased kidney function who are taking ketoconazole, itraconazole, ritonavir or clarithromycin.
- Children under 18 years old as the safety and effectiveness of this medicine have not been studied in children under 18 years old.
This medicine should not be used if you are allergic to any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.
If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.
Pregnancy and breastfeeding
Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.
- The safety of this medicine for use in pregnancy has not been established. It should not be used during pregnancy. Seek medical advice from your doctor. The manufacturer recommends that women who could get pregnant should use contraception to avoid pregnancy while taking this medicine.
- If you do get pregnant or want to plan a pregnancy while taking this medicine it is important to consult your doctor straight away for advice.
- It is not known if this medicine passes into breast milk. The manufacturer recommends that it is avoided in breastfeeding mothers. Seek medical advice from your doctor.
Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.
Common (affect between 1 in 10 and 1 in 100 people)
- Urinary tract infection.
- Faster than normal heartbeat (tachycardia).
Uncommon (affect between 1 in 100 and 1 in 1000 people)
- Vaginal infections such as vaginal thrush.
- Vaginal and vulval itching.
- Awareness of your heartbeat (palpitations).
- Irregular heartbeat (atrial fibrillation).
- Inflammation of the stomach (gastritis).
- Indigestion (dyspepsia).
- Increased blood pressure.
- Swelling of the joints.
- Rash or itching.
Rare (affect between 1 in 1000 and 1 in 10,000 people)
- Swelling of eyelids or lips.
- Red or purple areas of skin discolouration caused by bleeding under the skin (purpura).
The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.
For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.
How can this medicine affect other medicines?
It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to make sure that the combination is safe.
There may be an increased risk of abnormal heart rhythms (prolonged QT interval on a heart monitoring trace or ECG) if this medicine is taken in combination with any of the following medicines:
- antiarrhythmics (medicines to treat abnormal heart beats), eg amiodarone, procainamide, disopyramide, sotalol
- the antihistamines astemizole, mizolastine or terfenadine
- arsenic trioxide
- certain antidepressants, eg amitriptyline, imipramine, maprotiline
- certain antimalarials, eg halofantrine, chloroquine, quinine, mefloquine, Riamet
- certain antipsychotics, eg thioridazine, haloperidol, sertindole, pimozide
- intravenous erythromycin or pentamidine
The following medicines may reduce the breakdown of mirabegron by the liver and so may increase the amount of the medicine in the blood. If you are taking any of these and you have mild liver or kidney problems, your daily dose of this medicine may be reduced to 25mg daily:
The medicines listed above should not be taken in combination with this medicine if you have severely decreased kidney function or moderately decreased liver function. (Your doctor will know.)
Mirabegron can increase the level of digoxin in the blood. If you are taking this medicine in combination with digoxin your doctor will monitor your digoxin levels and may decrease your digoxin dose if necessary.
Mirabegron may also increase the blood levels of the following medicines, which could increase the risk of their side effects:
Other medicines containing the same active ingredient
There are currently no other medicines available in the UK that contain mirabegron as the active ingredient.