Overactive Bladder Pharmacotherapy

Overactive Bladder Pharmacotherapy

1. Definition, terminology & clinical syndrome

• Overactive bladder (OAB) is a symptom syndrome defined by urinary urgency, usually accompanied by frequency and nocturia, with or without urgency urinary incontinence (UUI), in the absence of urinary-tract infection or other obvious pathology — the symptom complex maps mechanistically onto detrusor overactivity during the storage phase (G&G 14e Ch.11, pp.215–6).
• Urgency = the sudden, compelling desire to void that is difficult to defer; it is the cornerstone symptom distinguishing OAB from simple increased frequency (G&G 14e Ch.11, p.216).
• Urgency urinary incontinence (UUI) = involuntary leakage accompanied by/preceded by urgency; contrasts with stress incontinence (leakage on effort/exertion, a sphincteric/anatomical problem not primarily drug-treated) — antimuscarinics and β₃-agonists treat the urgency/UUI component, not stress leakage (G&G 14e Ch.11, p.216).
• Antimuscarinic therapy targets the storage abnormality by acting to lower intravesical pressure, increase functional bladder capacity, and reduce the frequency of (uninhibited) detrusor contractions (G&G 14e Ch.11, p.216).
• Detrusor instability / detrusor hyperreflexia is the older terminology KDT uses; "vasicoselective" antimuscarinics (oxybutynin, tolterodine, etc.) are deployed for detrusor instability resulting in urinary frequency and urge incontinence (KDT 8e Ch.8, p.129).
• OAB is sub-classified by aetiology into idiopathic (no identifiable neurological cause — the majority) and neurogenic detrusor overactivity (secondary to suprapontine or suprasacral spinal cord lesions — e.g., stroke, multiple sclerosis, spinal cord injury, spina bifida); both respond to antimuscarinics, but the neurogenic group is the classical target for intravesical and higher-dose strategies (G&G 14e Ch.11, p.216; KDT 8e Ch.8, p.129).
• Other storage-phase indications addressed by the same drug class in the source chapters: nocturnal enuresis in children (where a progressive increase in bladder capacity is the objective) and spastic paraplegia (reduce frequency, increase capacity) (G&G 14e Ch.11, p.216).