What Is The Dosage And Time For Diuretic?

Is there a time released diuretic? My mother-in-law takes Diamox and furosemide during the day, but she urinates more at night when she hasn't taken any diuretics. She is now out of hospital and rehab. She has come to stay with us, she is no longer able to be home alone. She has to have assistance to the restroom, and goes about every hour to hour and half, so we are getting no rest or sleep. She also has some renal problems and only allowed 1500ml of fluid daily, so she isn't drinking all day. Any suggestions would be appreciated. Thank you.