Oral Hyperphosphataemia in patients with chronic renal failure Adult: Initially, 2.5 g daily, given in divided doses, may increase up to 17 g daily in divided doses if needed. Renal impairment:CrCl (ml/min)Dosage Recommendation<25Dosage adjustments may be needed depending on serum calcium levels.AdministrationMay be taken with or without food. Take with meals for better absorption. Avoid taking w/ large amount of fibre-rich food. ContraindicationsPatients with Ca renal calculi or history of renal calculi; hypercalcaemia; hypophosphataemia. Patients with suspected digoxin toxicity.Special PrecautionsRenal impairment, hypoparathyroid disease, hypercalcaemia-associated diseases. Calcium absorption is impaired in achlorhydria; use an alternate salt and take with food. Caution when used in patients with a history of kidney stones.Adverse Drug ReactionsConstipation, flatulence; hypercalcaemia; metabolic alkalosis; milk-alkali syndrome, tissue-calcification. Gastric hypersecretion and acid rebound (with prolonged use).Drug InteractionsCo-administration with thiazide diuretics or vit D may lead to milk-alkali syndrome and hypercalcaemia. Decreased absorption with corticosteroids. Decreases absorption of tetracyclines, atenolol, iron, quinolones, alendronate, Na fluoride, Zn and calcium-channel blockers. Enhances cardiac effects of digitalis glycosides and may precipitate digitalis intoxication. Food InteractionAbsorption may be increased with food. Decreased absorption with bran, foods high in oxalates and whole grain cereals. Calcium may reduce iron absorption.Pregnancy Category (US FDA)Category CMechanism of ActionCalcium carbonate can neutralise gastric acid rapidly and effectively. However, it may adversely activate Ca dependent processes, leading to secretion of gastric and hydrochloric acid. It can induce rebound acid secretion and, prolonged high doses may cause hypercalcemia, alkalosis and milk-alkali syndrome. Absorption: Converted to calcium chloride by gastric acid. Some of the calcium is absorbed in the intestines. Calcium is absorbed in soluble, ionized form; solubility of calcium is increased in an acidic environment. Distribution: Crosses placenta, enters breast milk. Excretion: Mainly in the faeces as unabsorbed calcium; urine (20%).