Why Does It Say To Not Store Magnesium Citrate In

Why does it say to not store magnesium citrate in the refrigerator? Also, why must it be used in 24 hours? I have to take it @ once a month. Had diverticulitus and a foot of my colon removed. Have constant constipation. Have used stool softeners, fiber, sennocot and miralax. Had a colonscopy and endoscopy recently. Doctor said nothing unusual. He did remove several pre-cancerous pollips. (Please excuse spelling) Mother had colon canser. Aunt had stomach cancer. Thanks for any help.