How Long Can Course Of Sodium Picosulfate Be Taken?

My daughter, 5yrs, is on Sodium Picosulfate, varying from 2.5mls to 10mls, she has been on this for 2months now, how long will she have to remain on it and does she need to have regular blood test done while on this? She has had bowel problems since aged 3yrs, she also had renal reflux as a baby.