indication

Calcium acetate is one of a number of calcium salts used to treat hyperphosphatemia (too much phosphate in the blood) in patients with kidney disease.

pharmacology

Patients with advanced renal insufficiency (creatinine clearance less than 30 ml/min) exhibit phosphate retention and some degree of hyperphosphatemia. The retention of phosphate plays a pivotal role in causing secondary hyperparathyroidism associated with osteodystrophy, and soft-tissue calcification. The mechanism by which phosphate retention leads to hyperparathyroidism is not clearly delineated. Therapeutic efforts directed toward the control of hyperphosphatemia include reduction in the dietary intake of phosphate, inhibition of absorption of phosphate in the intestine with phosphate binders, and removal of phosphate from the body by more efficient methods of dialysis. The rate of removal of phosphate by dietary manipulation or by dialysis is insufficient. Dialysis patients absorb 40% to 80% of dietary phosphorus. Therefore, the fraction of dietary phosphate absorbed from the diet needs to be reduced by using phosphate binders in most renal failure patients on maintenance dialysis. Calcium acetate when taken with meals combines with dietary phosphate to form insoluble calcium phosphate which is excreted in the feces. Maintenance of serum phosphorus below 6.0 mg/dl is generally considered as a clinically acceptable outcome of treatment with phosphate binders. Calcium acetate is highly soluble at neutral pH, making the calcium readily available for binding to phosphate in the proximal small intestine.

mechanism of action

Calcium acetate and other calcium salts are phosphate binders. They work by binding with the phosphate in the food you eat, so that it is eliminated from the body without being absorbed.

toxicity

Oral, rat: LD₅₀ = 4280 mg/kg. Symptoms of overdose include mild hypercalcemia (constipation; loss of appetite; nausea and vomiting), and severe hypercalcemia (confusion; full or partial loss of consciousness; incoherent speech).

absorption

40% is absorbed in the fasting state and approximately 30% is absorbed in the nonfasting state following oral administration.

route of elimination

Calcium acetate when taken with meals, combines with dietary phosphate to form insoluble calcium phosphate which is excreted in the feces.

drug interactions

Alendronate: Calcium Salts may decrease the serum concentration of Bisphosphonate Derivatives such as alendronate. Avoid administration of oral calcium supplements within 30 minutes after alendronate.

Calcium carbonate: Calcium salts may enhance the adverse/toxic effect of calcium acetate. Concurrent use of other calcium salts with calcium acetate should be avoided when possible. This combination is particularly dangerous in patients with other risk factors for hypercalcemia, such as those with end-stage renal disease.

Calcium Chloride: Calcium salts may enhance the adverse/toxic effect of calcium acetate. Concurrent use of other calcium salts with calcium acetate should be avoided when possible. This combination is particularly dangerous in patients with other risk factors for hypercalcemia, such as those with end-stage renal disease.

Ceftriaxone: Calcium Salts (Intravenous) may enhance the adverse/toxic effect of Ceftriaxone. Ceftriaxone binds to calcium forming an insoluble precipitate. Concurrent or sequential use (within 48 hours) of ceftriaxone with calcium-containing solutions is contraindicated in neonates (28 days of age or younger). In other patients, these solutions can be used sequentially if the infusion lines are flushed with a compatible fluid between ceftriaxone and calcium-containing solution infusion.

Ciprofloxacin: Calcium salts such as calcium acetate may decrease the absorption of quinolone antibiotics such as ciprofloxacin. Of concern only with oral administration of both agents. Interactions can be minimized by administering oral quinolone at least 2 hours before, or 6 hours after, the dose of an oral calcium supplement. Monitor for decreased therapeutic effects of oral quinolones if administered with oral calcium supplements.

Clodronate: Calcium Salts may decrease the serum concentration of Bisphosphonate Derivatives such as clodronate. Avoid administration of oral calcium supplements within 2 hours before or after tiludronate/clodronate/etidronate.

Demeclocycline: Calcium salts such as calcium acetate may decrease the serum concentration of tetracycline derivatives such as demeoclocycline. In general, the coadministration of oral calcium salts and oral tetracycline derivatives should be avoided. Interactions may be able to be minimized by administering oral calcium preparations several hours before or after the dose of the oral tetracycline derivatives. Even with dose separation, therapy may still be compromised. Monitor for decreased therapeutic effect of oral tetracycline derivatives.

Doxycycline: Calcium salts such as calcium acetate may decrease the serum concentration of tetracycline derivatives such as doxycycline. In general, the coadministration of oral calcium salts and oral tetracycline derivatives should be avoided. Interactions may be able to be minimized by administering oral calcium preparations several hours before or after the dose of the oral tetracycline derivatives. Even with dose separation, therapy may still be compromised. Monitor for decreased therapeutic effect of oral tetracycline derivatives.

Estramustine: Calcium salts such as calcium acetate may decrease the absorption of estramustine. Interactions can be minimized by administering estramustine on an empty stomach, at least 1 hour before or 2 hours after the dose of an oral calcium supplement. Do not coadminister estramustine with food or milk. Monitor for decreased therapeutic effects of estramustine if administered with oral calcium supplements, food or milk.

Etidronic acid: Calcium Salts may decrease the serum concentration of Bisphosphonate Derivatives such as etidronic acid (etidronate). Avoid administration of oral calcium supplements within 2 hours before or after tiludronate/clodronate/etidronate.

Gemifloxacin: Calcium salts such as calcium acetate may decrease the absorption of quinolone antibiotics such as gemifloxacin. Of concern only with oral administration of both agents. Interactions can be minimized by administering oral quinolone at least 2 hours before, or 6 hours after, the dose of an oral calcium supplement. Monitor for decreased therapeutic effects of oral quinolones if administered with oral calcium supplements.

Ibandronate: Calcium Salts may decrease the serum concentration of Bisphosphonate Derivatives such as ibandronate. Avoid administration of oral calcium supplements within 60 minutes after oral ibandronate.

Levofloxacin: Calcium salts such as calcium acetate may decrease the absorption of quinolone antibiotics such as levofloxacin. Of concern only with oral administration of both agents. Interactions can be minimized by administering oral quinolone at least 2 hours before, or 6 hours after, the dose of an oral calcium supplement. Monitor for decreased therapeutic effects of oral quinolones if administered with oral calcium supplements.

Levothyroxine: Calcium salts such as calcium acetate may diminish the therapeutic effect of thyroid products such as levothyroxine. Separate the doses of the thyroid product and the oral calcium supplement by at least 4 hours. Monitor for decreased therapeutic effects of thyroid products if an oral calcium supplement is initiated/dose increased, or increased effects if an oral calcium supplement is discontinued/dose decreased.

Liothyronine: Calcium salts such as calcium acetate may diminish the therapeutic effect of thyroid products such as liothyronine. Separate the doses of the thyroid product and the oral calcium supplement by at least 4 hours. Monitor for decreased therapeutic effects of thyroid products if an oral calcium supplement is initiated/dose increased, or increased effects if an oral calcium supplement is discontinued/dose decreased.

Liotrix: Calcium salts such as calcium acetate may diminish the therapeutic effect of thyroid products such as liotrix. Separate the doses of the thyroid product and the oral calcium supplement by at least 4 hours. Monitor for decreased therapeutic effects of thyroid products if an oral calcium supplement is initiated/dose increased, or increased effects if an oral calcium supplement is discontinued/dose decreased.

Lomefloxacin: Calcium salts such as calcium acetate may decrease the absorption of quinolone antibiotics such as lomefloxacin. Of concern only with oral administration of both agents. Interactions can be minimized by administering oral quinolone at least 2 hours before, or 6 hours after, the dose of an oral calcium supplement. Monitor for decreased therapeutic effects of oral quinolones if administered with oral calcium supplements.

Minocycline: Calcium salts such as calcium acetate may decrease the serum concentration of tetracycline derivatives such as minocycline. In general, the coadministration of oral calcium salts and oral tetracycline derivatives should be avoided. Interactions may be able to be minimized by administering oral calcium preparations several hours before or after the dose of the oral tetracycline derivatives. Even with dose separation, therapy may still be compromised. Monitor for decreased therapeutic effect of oral tetracycline derivatives.

Nalidixic Acid: Calcium salts such as calcium acetate may decrease the absorption of quinolone antibiotics such as nalidixic acid. Of concern only with oral administration of both agents. Interactions can be minimized by administering oral quinolone at least 2 hours before, or 6 hours after, the dose of an oral calcium supplement. Monitor for decreased therapeutic effects of oral quinolones if administered with oral calcium supplements.

Norfloxacin: Calcium salts such as calcium acetate may decrease the absorption of quinolone antibiotics such as norfloxacin. Of concern only with oral administration of both agents. Interactions can be minimized by administering oral quinolone at least 2 hours before, or 6 hours after, the dose of an oral calcium supplement. Monitor for decreased therapeutic effects of oral quinolones if administered with oral calcium supplements.

Ofloxacin: Calcium salts such as calcium acetate may decrease the absorption of quinolone antibiotics such as ofloxacin. Of concern only with oral administration of both agents. Interactions can be minimized by administering oral quinolone at least 2 hours before, or 6 hours after, the dose of an oral calcium supplement. Monitor for decreased therapeutic effects of oral quinolones if administered with oral calcium supplements.

Risedronate: Calcium Salts may decrease the serum concentration of Bisphosphonate Derivatives such as risedronate. Avoid administration of oral calcium supplements within or 30 minutes after risedronate.

Sparfloxacin: Calcium salts such as calcium acetate may decrease the absorption of quinolone antibiotics such as sparfloxacin. Of concern only with oral administration of both agents. Interactions can be minimized by administering oral quinolone at least 2 hours before, or 6 hours after, the dose of an oral calcium supplement. Monitor for decreased therapeutic effects of oral quinolones if administered with oral calcium supplements.

Tetracycline: Calcium salts such as calcium acetate may decrease the serum concentration of tetracycline derivatives such as tetracycline. In general, the coadministration of oral calcium salts and oral tetracycline derivatives should be avoided. Interactions may be able to be minimized by administering oral calcium preparations several hours before or after the dose of the oral tetracycline derivatives. Even with dose separation, therapy may still be compromised. Monitor for decreased therapeutic effect of oral tetracycline derivatives.

Tiludronate: The divalent cation of oral Calcium Acetate may significantly decrease the absorption of Tiludronate by forming a nonabsorbable chelate. Oral dosing should be separated by at least 2 hours.

Trovafloxacin: Calcium may decrease the absorption of orally administered Trovafloxacin. Administer Trovafloxacin 2 hours before or 6 hours after a dose of the calcium containining agent to minimize the interaction.