 [ Symptoms ] what is the reason for my arm pain [ Disease ] i am sorry to hear about your dad is cancer but how lucky he is to have you to help him through this it sounds like you have been doing a great job managing your dad is constipation as you know opioid narcotic pain medications can cause constipation the stool softeners were a good idea as was the miralax if the miralax was working but then caused diarrhea you may need to keep playing with how much and how often to use it in order to achieve the desired result if your dad is experiencing constipation you can give him the miralax even if it means you are off schedule with it do not get stuck in a schedule if it is not working because your dad has colon cancer specifically and he is now experiencing problems with bowel movements it would be a good idea to make an appointment to see his health care provider this increase in constipation along with the cramping could be related to the disease progression and should be evaluated by his primary care provider or oncologist i wish you all the very best as you go through this journey hang in there