5.1 Hypercalcemia

Patients with end stage renal disease may develop hypercalcemia when treated with calcium, including calcium acetate.  Avoid the use of calcium supplements, including calcium-based nonprescription antacids, concurrently with calcium acetate.

An overdose of calcium acetate may lead to progressive hypercalcemia, which may require emergency measures.  Therefore, early in the treatment phase during the dosage adjustment period, monitor serum calcium levels twice weekly.  Should hypercalcemia develop, reduce the calcium acetate dosage or discontinue the treatment, depending on the severity of hypercalcemia.

More severe hypercalcemia (Ca>12 mg/dL) is associated with confusion, delirium, stupor and coma.  Severe hypercalcemia can be treated by acute hemodialysis and discontinuing calcium acetate therapy.

Mild hypercalcemia (10.5 to 11.9 mg/dL) may be asymptomatic or manifest as constipation, anorexia, nausea, and vomiting.  Mild hypercalcemia is usually controlled by reducing the calcium acetate dose or temporarily discontinuing therapy.  Decreasing or discontinuing Vitamin D therapy is recommended as well.

Chronic hypercalcemia may lead to vascular calcification and other soft-tissue calcification.  Radiographic evaluation of suspected anatomical regions may be helpful in early detection of soft tissue calcification.  The long term effect of calcium acetate on the progression of vascular or soft tissue calcification has not been determined.

Hypercalcemia (>11 mg/dL) was reported in 16% of patients in a 3-month study of a solid dose formulation of calcium acetate; all cases resolved upon lowering the dose or discontinuing treatment.

Maintain the serum calcium-phosphorus (Ca x P) product below 55 mg2/dL2.

5.2 Concomitant Use with Medications

Hypercalcemia may aggravate digitalis toxicity.

6.1 Clinical Trial Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

In clinical studies, calcium acetate has been generally well tolerated.

Calcium acetate was studied in a 3-month, open-label, non-randomized study of 98 enrolled ESRD hemodialysis patients and in a two week double-blind, placebo-controlled, cross-over study with 69 enrolled ESRD hemodialysis patients.  Adverse reactions (>2% on treatment) from these trials are presented in Table 1.

Mild hypercalcemia may be asymptomatic or manifest itself as constipation, anorexia, nausea, and vomiting.  More severe hypercalcemia is associated with confusion, delirium, stupor, and coma.  Decreasing dialysate calcium concentration could reduce the incidence and severity of calcium acetate-induced hypercalcemia.  Isolated cases of pruritus have been reported, which may represent allergic reactions.

6.2 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 post-approval of calcium acetate:  dizziness, edema, and weakness.

7.1 Ciprofloxacin

In a study of 15 healthy subjects, a co-administered single dose of 4 calcium acetate tablets approximately 2.7 g, decreased the bioavailability of ciprofloxacin by approximately 50%.

8.1 PREGNANCY

Pregnancy Category C

Calcium acetate tablets contain calcium acetate.  Animal reproduction studies have not been conducted with calcium acetate, and there are no adequate and well controlled studies of calcium acetate use in pregnant women.  Patients with end stage renal disease may develop hypercalcemia with calcium acetate treatment [see Warnings and Precautions (5.1)].  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.  Calcium acetate treatment, as recommended, is not expected to harm a fetus if maternal calcium levels are properly monitored during and following treatment.

8.2 LABOR & DELIVERY

The effects of calcium acetate on labor and delivery are unknown.

8.3 NURSING MOTHERS

Calcium acetate tablet contains calcium acetate and is excreted in human milk.  Human milk feeding by a mother receiving calcium acetate is not expected to harm an infant, provided maternal serum calcium levels are appropriately monitored.

8.4 PEDIATRIC USE

Safety and effectiveness in pediatric patients have not been established.

8.5 GERIATRIC USE

Clinical studies of calcium acetate did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects.  Other clinical experience has not identified differences in responses between the elderly and younger patients.  In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

12.1 MECHANISM OF ACTION

Calcium acetate, when taken with meals, combines with dietary phosphate to form an insoluble calcium phosphate complex, which is excreted in the feces, resulting in decreased serum phosphorus concentration.

12.2 PHARMACODYNAMICS

Orally administered calcium acetate from pharmaceutical dosage forms is systemically absorbed up to approximately 40% under fasting conditions and up to approximately 30% under non-fasting conditions. This range represents data from both healthy subjects and renal dialysis patients under various conditions.

13.1 CARCINOGENESIS & MUTAGENESIS & IMPAIRMENT OF FERTILITY

No carcinogenicity, mutagenicity, or fertility studies have been conducted with calcium acetate.