Originally published on: April 6th, 2017. Last modified on October 5th, 2021

Betmiga contains the active substance mirabegron. It is a bladder muscle relaxant (a so called oral β3-adrenoceptor agonist), which reduces the activity of an overactive bladder and treats the related symptoms. Launched in 2013 it is the first compound to obtain a license in this new class of treatment for OAB, using an alternative mechanism of action compared to antimuscarinics.

Betmiga is used to treat the symptoms of an overactive bladder in adults such as:

  • suddenly needing to empty your bladder (called urgency)
  • having to empty your bladder more than usual (called increased urinary frequency)
  • not being able to control when to empty your bladder (called urgency incontinence)

Betmiga Side Effects

An uncommon but serious Betmiga side effect (may affect up to 1 in 100 people) may include irregular heart beat (atrial fibrillation). If this side effect occurs, immediately stop taking the medicine and seek urgent medical advice.

Common side effects

These may affect up to 1 in 10 people:

  • Increased heart rate (tachycardia)
  • Infection of the structures that carry urine (urinary tract infections)

Uncommon side effects

These may affect up to 1 in 100 people:

  • Bladder infection (cystitis)
  • Feeling your heartbeat (palpitations)
  • Vaginal infection
  • Indigestion (dyspepsia)
  • Infection of the stomach (gastritis)
  • Swelling of the joints
  • Itching of the vulva or vagina (vulvovaginal pruritus)
  • Increased blood pressure
  • Increase in liver enzymes (GGT, AST and ALT)
  • Itching, rash or hives (urticaria, rash, rash macular, rash papular, pruritus)

Further Information

As with any medicine, if you feel unwell after taking Mirabegron you should seek medical advice. Contact your prescriber, pharmacist, nurse or call NHS non-emergency number on 111 (You should use the NHS 111 service if you urgently need medical help or advice but it’s not a life-threatening situation)