Why does takn certain meds.cause bedwettn?like sleep meds.or muscle relaxers?

Sphincter or Bladder: The sleep medication or muscle relaxation can cause a relaxation in the sphincter, which is very short in women. When the sphincter relaxes too much, the urine can't be stored and leakage then results. There are other causes, including overactive bladder, 'spasm' of the bladder at night, and rarer causes. Adjusting the medications and a urology consult would be advisable.