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Drug management of overactive bladder (OAB)

There are 2 main classes of drugs available to treat this problem: “anticholinergic” medications and “selective beta-3 adrenergic agonists”.

Both of these classes of medication are thought to act:

  • By changing abnormal nerve signalling in the nerve pathways of the bladder and
  • By relaxing the bladder muscle and helping to prevent involuntary bladder muscle contractions

Anticholinergic Medications

Anticholinergic medications available in Australia include (in alphabetical order; no hierarchy is implied):

  • Darifenacin – marketed as Enablex®
  • Oxybutynin
    • oral Oxybutynin – marketed as Ditropan®
    • transdermal (skin patch formulation) Oxybutynin-marketed as the Oxytrol Patch®
  • Solifenacin – marketed as Vesicare®
  • Tolterodine – marketed as Detrusitol®

All the anticholinergic medications have approximately the same efficacy in reducing urgency, frequency and episodes of urge incontinence.

The newer preparations such as darifenacin (Enablex®), solifenacin (Vesicare®) and transdermal oxybutynin (Oxytrol patch®) have the advantage of fewer side effects as they are extended release preparations.

The most common potential side effects of this group of medications include:

  • Dry mouth – caused by reduced saliva production is the most common side effect
  • Constipation
  • Dry eyes
  • Blurred vision
  • Indigestion or heartburn

If symptoms are not controlled with one of the medications in this group (or if side- effects occur that are poorly tolerated), then a different anticholinergic medication can be tried or the dose of the medication changed.

Generally a trial of at least 4-6 weeks is needed to assess if an anticholinergic medication is effective in treating the symptoms of OAB.

Medication can be combined with behavioural therapies such as bladder retraining and pelvic floor physiotherapy to improve effectiveness.

Selective Beta-3 Adrenergic Agonist medications

Selective beta-3 adrenergic agonist medications were first released in 2014 in Australia for the treatment of overactive bladder. Mirabegron (marketed as Betmiga® in Australia) is the first drug of this class to be commercially available. Mirabegron works by relaxing the smooth muscle of the bladder to allow the bladder to store urine more easily.

Mirabegron is well tolerated due to the lack of the common anticholinergic side effects (such as dry mouth) with this different class of medication.

Mirabegron should not be used in people with severe uncontrolled high blood pressure as it has the potential to increase blood pressure. People with well-controlled blood pressure on antihypertensive (blood pressure lowering) medication can safely use Mirabegron.

Topical Oestrogen in Postmenopausal Women

Postmenopausal women with dry vaginal and urethral tissues can also be treated with local vaginally inserted oestrogen cream. This is not the same as a hormone tablet or patch that is designed to raise blood levels of oestrogen.

Local or topical oestrogen pessaries (i.e. an oestrogen cream or pessary tablet inserted internally into the vagina) aim to treat only the dry vaginal tissues, which can contribute to overactive bladder symptoms in some women (as well as potentially to treat recurrent urinary tract infections). Ovestin® cream or Vagifem Low® pessaries are prescribed twice weekly for this purpose.