An overactive bladder is a problem with the storage function of the bladder, resulting in a sudden urge to urinate that may be difficult to resist. It is caused by urinary muscle spasms and can have a number of root causes, such as being overweight, genetic weaknesses, bladder inflammation or multiple pregnancies. 

There are a number of different kinds of urinary incontinence. Stress incontinence is when bladder pressure causes urine leakage. Urge incontinence is urine leakage as you feel a sudden urge to urinate. Overflow incontinence is the inability to fully empty the bladder, resulting in frequent leaking. Total incontinence is when the bladder is totally unable to store urine, causing you to urinate or leak constantly.

Treatments are available depending on the severity of the case and the form of incontinence suffered. Medication, maintaining a healthy weight, bladder training, scheduling toilet trips and doing pelvic floor muscle exercises may be used in a course of treatment.

Commonly prescribed drug classes used to treat an overactive bladder include beta-agonists, anticholinergics, and antimuscinarics.