PHOSLYRA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PHOSLYRA (PHOSLYRA).
Phoslyra (calcium acetate) binds dietary phosphate in the gastrointestinal tract, forming insoluble calcium phosphate complexes that are excreted in the feces, thereby reducing serum phosphate levels.
| Metabolism | Calcium acetate is not metabolized; it dissociates to release calcium ions which are partially absorbed, but the majority of the calcium-phosphate complex is excreted in feces. |
| Excretion | Renal 100% as unchanged drug, no biliary or fecal elimination. |
| Half-life | Not applicable; Phoslyra (calcium acetate) is not absorbed systemically; local effect in GI tract. |
| Protein binding | Not applicable (no systemic absorption). |
| Volume of Distribution | Not applicable (no systemic absorption). |
| Bioavailability | Oral bioavailability is negligible (<0.1%); acts locally. |
| Onset of Action | Immediately upon oral administration; binds dietary phosphate in GI tract. |
| Duration of Action | Duration equals GI transit time (~3-4 hours); requires administration with each meal. |
| Molecular Weight | 158.17 Da (calcium acetate) |
1330 mg (one caplet) orally three times daily with meals, titrated to achieve serum phosphorus within target range.
| Dosage form | SOLUTION |
| Renal impairment | No dose adjustment required for GFR 15-59 mL/min. For GFR <15 mL/min or dialysis, starting dose 1330 mg three times daily with meals, titrate per serum phosphorus. |
| Liver impairment | No specific adjustments for hepatic impairment; use with caution in severe impairment. |
| Pediatric use | Not established for children under 18 years; safety and efficacy not determined. |
| Geriatric use | No specific geriatric dose adjustment; monitor renal function and serum calcium/phosphorus. |
| 1st trimester | Calcium acetate is classified as FDA pregnancy category C. No adequate and well-controlled studies in pregnant women. Animal reproduction studies have not been conducted. Use only if clearly needed and potential benefit justifies risk to fetus. |
| 2nd trimester | Same as T1. Avoid hypercalcemia which may cause fetal harm. |
| 3rd trimester | Same as T1. Potential for neonatal hypocalcemia if maternal hypercalcemia occurs. |
Clinical note
Comprehensive clinical and safety monograph for PHOSLYRA (PHOSLYRA).
| Placental transfer | Calcium acetate is a salt that dissociates into calcium and acetate ions. Calcium is actively transported across the placenta, but the contribution from calcium acetate is minimal. Acetate is metabolized. No data on placental transfer of the intact drug; likely low. |
| Breastfeeding | Calcium acetate is expected to be excreted into human breast milk in small amounts. However, due to its poor systemic absorption, it is unlikely to pose a significant risk to the nursing infant. Use with caution, monitoring infant for signs of hypercalcemia. |
■ FDA Black Box Warning
None
| Serious Effects |
HypercalcemiaHypersensitivity to calcium acetate or any component of the formulation
| Precautions | Hypercalcemia may occur; monitor serum calcium levels regularly. Avoid use with vitamin D analogs unless calcium levels are monitored. Use with caution in patients with arrhythmias, renal stones, or sarcoidosis. Ensure adequate hydration to prevent constipation. |
| Food/Dietary | Phoslyra should be taken with food to bind dietary phosphate. Avoid high-phosphate foods such as dairy products, nuts, seeds, beans, cola, and processed foods. Concomitant administration with calcium-containing foods or supplements may increase risk of hypercalcemia. Separate dosing from oral medications by at least 1 hour if possible, as calcium acetate can bind other drugs. |
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| Lactation Rating | L2 - Safer |
| Teratogenic Risk | Phoslyra (calcium acetate) is a phosphate binder. No teratogenic effects have been reported in animal studies; however, there are no adequate and well-controlled studies in pregnant women. Hypercalcemia during pregnancy may lead to adverse fetal effects including hypotonia, seizures, and cardiac abnormalities. Risk is dose-dependent. |
| Fetal Monitoring | Maternal serum calcium and phosphate levels should be monitored regularly. Fetal monitoring may include ultrasound for signs of hypercalcemia-related effects, though specific guidelines are not established. |
| Fertility Effects | No known effects on fertility. Calcium acetate does not directly impair reproductive function, but underlying renal disease may affect fertility. |
| Clinical Pearls | Phoslyra (calcium acetate) is a phosphate binder used in end-stage renal disease (ESRD). Administer with meals to bind dietary phosphate. Monitor serum calcium and phosphate levels; hypercalcemia can occur, especially with concurrent vitamin D or calcium supplements. Avoid in patients with hypercalcemia. Use with caution in patients with cardiac arrhythmias or digitalis toxicity due to calcium effects. |
| Patient Advice | Take Phoslyra exactly as prescribed with each meal or snack to control phosphate levels. · Do not skip meals or take the medication on an empty stomach. · Adhere to a low-phosphate diet as recommended by your healthcare provider. · Inform your doctor if you experience nausea, vomiting, constipation, or signs of high calcium (e.g., confusion, muscle weakness, bone pain). · Do not take additional calcium supplements without your doctor's approval. |