Hello, Since he needs to take morphine for the control of pain and constipation is an important side effect of morphine hence the best medicine to reverse this side effect would be Relistore. In addition he may be given traditional laxatives such as bisacodyl or senna or polyethylene glycol) which are equally effective in relieving constipation. Along with the above medications, he should be encouraged to increase the fluid and fruits/vegetables intake as well as moderate physical activity as long as he can do. When appropriate, discourage the use of a bedpan, which is also associated with constipation. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Mohammed Taher Ali, General & Family Physician