see also:

• urology

• overactive bladder (OAB) is a troublesome condition resulting from detrusor overactivity which contracts inappropriately during bladder filling
• it has a serious impact on quality of life
• urinary incontinence is one of the commonest reasons for admission into a nursing home and increases risk of local skin infections and urinary tract infections (UTIs) / cystitis, while the constant smell of urine becomes a socially isolating problem
• ~50% of nursing home residents have OAB or urinary incontinence
• urgency increases falls risk in the elderly
• it is more common in those with:
  • type 1 diabetes mellitus
  • obesity - a risk factor only in women not men
  • post-menopausal oestrogen deficiency states
  • age > 75yrs due to decreased bladder capacity and changes in muscle tone
    • occurs in 20% of those over 70yrs and in 25% of those over 75yrs
  • depression
  • arthritis
  • prostatism
• Mx is aimed at treating the cause, using behavioural Rx and pharmacologic Rx to reduce detrusor contractions

• urinary frequency and nocturia
• +/- urinary urgency
• +/- urge incontinence

• stroke (CVA)
• spinal cord injury
• multiple sclerosis (MS)
• dementia
• Parkinson's disease
• medullary lesions
• diabetic neuropathy

• idiopathic (rare)
• increased pressure on the bladder:
  • postural changes, cough, walking
  • rapid filling of the bladder:
    • drinking a lot of water
    • diuretics
    • patients with peripheral oedema (eg. congestive cardiac failure) who elevate legs at night resulting in nocturia
• urinary tract infections (UTIs) / cystitis
• bladder cancer
• bladder stones
• bladder outlet obstruction (eg. prostatism)
• drugs eg. cholinergics such as bethanecol which stimulate detrusor contraction

• see anti-muscarinic anticholinergic agents
• selective muscarinic M3 receptor antagonists were introduced onto the Australian PBS for Rx of overactive bladders in 2005 onwards
• eg. Tolterodine tartrate, Darifenacin hydrobromide, Solifenacin succinate

• see beta 3 agonists
• mirabegron was introduced into the Australian PBS in 2013
  • it is only recommended when antimuscarinic agents are C/I, ineffective or not tolerated
  • it may cause hypertension, tachycardia, atrial fibrillation (in 1%) and it may interact with other medications such as digoxin, flecainide, tricyclic antidepressants
  • not for use in pregnancy or lactation as has reproductive toxicity
  • modest efficacy with incontinence episodes reduced by ~1.5 per day
  • terminal half-life is ~50hrs

• onabotulinumtoxinA significantly decreased the number of urinary incontinence episodes per day and improved quality of life in those with idiopathic overactive bladder not controlled by antimuscarinics