My boyfriend is going to take Magnesium Citrate, (10oz) for severe constipation. He is currently having daily doses of radiation for throat cancer. His Nurse did recommend this for constipation. He is 6ft 2in, 220 lbs. Can you estimate about how long before the laxative will take effect?
Hi, mag. Citrate is an osmotic purgative. It keeps water in the intestine so makes stools semisolid or liquid. We need to Chat Doctor.  The dose can be increased according to need, too much dose will cause diarrhea or smaller dose will not be effective. Along with that the intestinal movements should be adequate for progress of food bolus into gut further and expulsion of stools outside. Another important fact is there should not be obstruction in the gut. The most common cause of such obstruction is xenoliths in rectum. This is assessed by per-rectal examination. If xenoliths are present, they should be evacuated with the help of enema or may be manually. So consultation with a surgeon or a gastroenterologist will help u.