My Mother (age 88)has Chronic Constipation Problem. She Is A

my mother (age 88)has chronic constipation problem. She is a patient of CA breast, taking Anastrozole hormone and also have age related problems in hear & lungs. Now her big suffering is from costipation. One gastrologist prescribed duphalac 15-20 ml 4 times (as required) if problem persists enaema & then pegalup 12.5 - 25 ml. But our regular house physician told due to taking duphalac 4 times, she have discomfort feeling in abdomen . so stop duphalac and for 3 days use only enaema to clear bowel. What should we do?