Why Would My Gastro MD Refuse To Prescribe Percocet To

Why would my gastro MD refuse to prescribe Percocet to help me stop continual bowel movements. I had a recent kidney op. and Percocet was given for pain but I also noticed a great reduction in bowel movements the 5 days I took the Percocet. I have been given cholesteral scrips "off label" over the years to no avail. This stuff is the only thing that has worked, even Lomotil. I could help him out in case of an audit because of all the useless( and expensive) meds I've taken over the last 30 yrs. He has nothing to help me and won't order the stuff works. Do any gastro guys use Percocet off label?