calcium acetate
Brand: PhosLo, Eliphos
Prototype: sevelamer
Drug Class: phosphate binder
Drug Family: electrolyte agent
Subclass: calcium-based phosphate binder
Organ Systems: renal
Mechanism of Action
Dissociates in the GI tract to release calcium ions that bind dietary phosphate to form insoluble calcium phosphate complexes; these complexes are not absorbed and are excreted in feces, reducing phosphate absorption and lowering serum phosphate in patients with chronic kidney disease.
dietary phosphate (GI lumen)
Indications
- hyperphosphatemia in end-stage renal disease (dialysis patients)
Contraindications
- hypercalcemia
- hypersensitivity to calcium salts
- renal calculi (calcium-based)
Adverse Effects
Common
- hypercalcemia
- nausea
- constipation
- pruritus
Serious
- vascular calcification (from hypercalcemia)
- adynamic bone disease
- milk-alkali syndrome
Pharmacokinetics (ADME)
| Absorption | approximately 40% of calcium absorbed systemically when taken with meals; phosphate binding occurs in GI lumen |
| Distribution | calcium distributes widely; major component of bone |
| Metabolism | not applicable for phosphate-binding function |
| Excretion | unabsorbed calcium-phosphate complexes excreted in feces |
| Half-life | N/A |
| Onset | phosphate lowering within 1 week of consistent use |
| Peak | N/A |
| Duration | effect depends on consistent administration with meals |
| Protein Binding | N/A |
| Vd | N/A |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| fluoroquinolones and tetracyclines | calcium chelates these antibiotics, reducing their absorption; separate by at least 2 hours | moderate |
| levothyroxine | calcium reduces thyroid hormone absorption; separate by 4 hours | moderate |
| iron supplements | calcium decreases iron absorption; separate by 2 hours | moderate |
| digoxin | hypercalcemia potentiates digoxin toxicity | major |
Nursing Considerations
- Administer with each meal (not before or after) to maximize phosphate binding in the GI lumen; the dose must be individualized based on the serum phosphate level and dietary phosphate intake.
- Monitor serum calcium, phosphate, and intact PTH regularly; if serum calcium exceeds 10.5 mg/dL, reduce dose or switch to a non-calcium-based binder to prevent vascular calcification.
- Counsel dialysis patients about the risk of hypercalcemia from calcium-based binders, particularly when also receiving calcitriol or other vitamin D analogs that increase calcium absorption.
- Educate patients to take other oral medications at least 2 hours before or after calcium acetate to prevent chelation-based absorption interactions, particularly fluoroquinolones and levothyroxine.
Clinical Pearls
- Calcium acetate contains twice the elemental calcium per gram as calcium carbonate but is less soluble at higher pH values — in the alkaline environment of the small intestine, calcium acetate may be more effective at phosphate binding than calcium carbonate.
- Guidelines (KDIGO) recommend limiting calcium-based phosphate binders due to concerns about positive calcium balance and vascular calcification; non-calcium binders (sevelamer, lanthanum) are preferred when hypercalcemia is present or calcium load is a concern.
Safety Profile
Pregnancy generally-safe
Lactation safe
Renal Adjustment Not required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
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