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Label Changes for:

PhosLo (calcium acetate) 667 mg gelcaps

March 2011

Changes have been made to the WARNINGS, PRECAUTIONS and ADVERSE REACTIONS sections of the safety label.

Detailed View: Safety Labeling Changes Approved By FDA Center for Drug Evaluation and Research (CDER) – March 2011




  • Section Revised
Concomitant Use with Medications
  • Hypercalcemia may aggravate digitalis toxicity.


Clinical Trial Experience
  • section revised
Postmarketing Experience
  • Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to estimate their frequency or to establish a causal relationship to drug exposure.
  • The following additional adverse reactions have been identified during postapproval of calcium acetate: dizziness, edema, and weakness.


  • The drug interaction of PhosLo® is characterized by the potential of calcium to bind to drugs with anionic functions (e.g., carboxyl, and hydroxyl groups). PhosLo® may decrease the bioavailability of tetracyclines or fluoroquinolones via this mechanism.
  • There are no empirical data on avoiding drug interactions between calcium acetate or PhosLo and most concomitant drugs. When administering an oral medication with PhosLo where a reduction in the bioavailability of that medication would have a clinically significant effect on its safety or efficacy…
  • In a study of 15 healthy subjects, a co-administered single dose of 4 calcium acetate tablets, approximately 2.7g, decreased the bioavailability of ciprofloxacin by approximately 50%.


  • PhosLo contains calcium acetate. Animal reproduction studies have not been conducted with PhosLo, and there are no adequate and well controlled studies of PhosLo use in pregnant women. Patients with end stage renal disease may develop hypercalcemia with calcium acetate treatment.  Maintenance of normal serum calcium levels is important for maternal and fetal well being. Hypercalcemia during pregnancy may increase the risk for maternal and neonatal complications such as stillbirth, preterm delivery, and neonatal hypocalcemia and hypoparathyroidism. PhosLo treatment, as recommended, is not expected to harm a fetus if maternal calcium levels are properly monitored during and following treatment.
Labor and Delivery
  • The effects of PhosLo on labor and delivery are unknown.
Nursing Mothers
  • PhosLo contains calcium acetate and is excreted in human milk. Human milk feeding by a mother receiving PhosLo is not expected to harm an infant, provided maternal serum calcium levels are appropriately monitored.
Geriatric Use
  • Section revised