In the same way that the nerve supply to the uterus, vagina and vulva can be injured, the nerve supply to the bladder and the bowel can also be injured in childbirth, constipation, surgery, etc. Any injury causes sprouting of abnormal nerves from the cut surface of the nerve stump. Eventually there are sufficient new nerves so that increasing your bladder volume leads to pain or irritative bladder symptoms. Treatment with drugs attempts to block these nerves sending these messages to your brain.
Irritative bladder symptoms include frequency or urgency passing urine. “Frequency” means going to the bathroom to pass urine more often than usual. “Urgency” means having to rush to the bathroom. If you leak before you get there then that is “urge incontinence”. Normal adults pass urine 6-8 times per day with volumes of 200-400 millilitres, and they do not get up at night. If they do have to go regularly at night – “nocturnal frequency” then that is a serious problem. Blood in your urine – “haematuria” – is the primary symptom of bladder cancer and requires urgent investigation.
Oxybutinin, tolterodine, solifenacin, darifenacin are all drugs that block nerves in your bladder from sending messages to your brain that you need to pass urine. All suffer from the side effects of dry eyes and dry mouths that can be very irritating.