Tissue deposition of lanthanum particularly in bone, liver & stomach wall. Monitor serum Ca levels in patients w/ renal insufficiency. Monitor liver function tests. Patients predisposed to GI obstruction, ileus, subileus & perforation eg, those w/ altered GI anatomy (eg, diverticular disease, peritonitis, history of GI surgery, cancer & ulceration), hypomotility disorders (eg, constipation, diabetic gastroparesis), & those who concomitantly use medications known to potentiate these effects. Re-evaluate patients who develop severe constipation or other severe GI signs & symptoms. Patients w/ acute peptic ulcer, ulcerative colitis, Crohn's disease or bowel obstruction. Abdominal x-rays may have a radio-opaque appearance typical of an imaging agent. Monitor patients w/ hepatic impairment. Pregnancy. Discontinue breastfeeding during therapy. Childn <18 yr.