PhosLo (calcium acetate) is a prescription phosphate binder indicated for the reduction of serum phosphorus in patients with end-stage renal disease. It works by binding with dietary phosphate in the digestive tract to form an insoluble complex, which is then excreted in the feces, thereby preventing phosphate absorption into the bloodstream. This medication is a critical component in the management of mineral and bone disorder associated with chronic kidney disease, helping to mitigate long-term cardiovascular and skeletal complications. Proper use under medical supervision is essential to achieve optimal phosphorus control while minimizing risks of hypercalcemia.

Features

• Active ingredient: Calcium acetate (667 mg per tablet, equivalent to 169 mg elemental calcium)
• Formulation: Film-coated, oval-shaped tablets for oral administration
• Mechanism: Binds dietary phosphate in the gastrointestinal tract
• Prescription status: Rx-only medication requiring nephrologist supervision
• Manufacturing: Produced under current Good Manufacturing Practices (cGMP)
• Packaging: Available in bottles of 200 tablets with child-resistant caps

Benefits

• Effectively lowers serum phosphate levels toward target ranges in ESRD patients
• Helps reduce the risk of metastatic calcification and cardiovascular complications
• Supports management of chronic kidney disease-mineral and bone disorder (CKD-MBD)
• May decrease parathyroid hormone (PTH) levels when used as part of comprehensive care
• Provides calcium supplementation while controlling phosphorus absorption
• Contributes to improved long-term outcomes in renal failure patients

Common use

PhosLo is primarily prescribed for patients with end-stage renal disease (ESRD) who are on dialysis. It is used to control hyperphosphatemia, a common complication in renal failure where the kidneys cannot adequately excrete phosphate. The medication is typically administered with meals to maximize its phosphate-binding capacity as it acts directly on dietary phosphorus. Treatment is usually long-term and integrated into a comprehensive renal management plan that may include dietary phosphate restriction, dialysis parameters adjustment, and monitoring of calcium-phosphate product. Regular laboratory monitoring of serum phosphorus, calcium, and parathyroid hormone levels is essential throughout therapy.

Dosage and direction

The dosage of PhosLo must be individualized based on serum phosphorus levels and tailored to each patient’s meal patterns. The typical initial dose is 2 tablets with each meal, which may be adjusted gradually to achieve target phosphorus levels (generally 3.5-5.5 mg/dL). Tablets should be swallowed whole with water and taken immediately with meals or within 30 minutes of starting a meal. The maximum recommended daily dose is determined by the patient’s serum calcium levels, which should not exceed the upper limit of normal. Dose titration should occur in 1-2 tablet increments per meal at 2-3 week intervals based on frequent serum phosphorus measurements. Healthcare providers should provide specific instructions based on the patient’s dialysis schedule, meal composition, and laboratory values.

Precautions

Regular monitoring of serum calcium and phosphorus levels is mandatory during PhosLo therapy. Patients should be cautioned about the risk of hypercalcemia, especially when taking concomitant vitamin D supplements. Use with caution in patients with hypercalcemia, hypophosphatemia, or those with conditions that predispose to hypercalcemia (such as sarcoidosis). Calcium acetate may decrease the absorption of tetracycline antibiotics, thyroid medications, and iron supplements when taken concurrently. Patients should maintain adequate hydration unless contraindicated. Those with gastrointestinal conditions such as constipation, ileus, or bowel obstruction should use PhosLo cautiously as it may exacerbate these conditions. Pediatric use requires careful supervision due to developing bone structures and different calcium requirements.

Contraindications

PhosLo is contraindicated in patients with hypercalcemia (elevated serum calcium levels). It should not be used in patients with known hypersensitivity to calcium acetate or any component of the formulation. Contraindicated in patients with hypophosphatemia unless undergoing treatment for hyperphosphatemia. Not recommended for patients with calcium-containing renal calculi or history of nephrolithiasis without careful benefit-risk assessment. Avoid use in patients with acute pancreatitis or conditions associated with hypercalcemia such as certain malignancies, sarcoidosis, or untreated hyperparathyroidism. Should not be administered to patients with intestinal obstruction or ileus.

Possible side effects

The most common side effects include hypercalcemia (elevated serum calcium), which may manifest as nausea, vomiting, anorexia, constipation, dry mouth, thirst, polyuria, and cognitive changes. Gastrointestinal effects such as nausea, vomiting, diarrhea, or constipation may occur, particularly during dose initiation. Less frequently, patients may experience localized tissue calcification, pruritus, or rash. Severe hypercalcemia may lead to cardiac arrhythmias, confusion, lethargy, or coma in extreme cases. Long-term excessive calcium intake may contribute to milk-alkali syndrome. Some patients report metallic taste or gastrointestinal discomfort. Any signs of hypercalcemia should be promptly reported to healthcare providers for appropriate management.

Drug interaction

PhosLo may interact with several medication classes. It can reduce absorption of tetracycline antibiotics, quinolones, bisphosphonates, iron supplements, thyroid medications, and phenytoin when taken concomitatoously—separate administration by at least 2 hours. Concurrent use with vitamin D supplements or analogs may increase the risk of hypercalcemia. Thiazide diuretics may decrease calcium excretion and potentiate hypercalcemia. Corticosteroids may reduce calcium absorption. Concomitant use with calcium channel blockers may require dosage adjustments. PhosLo may bind to phosphate-containing medications. Digitalis toxicity may be potentiated by hypercalcemia. Always inform healthcare providers of all medications, including over-the-counter products and supplements.

Missed dose

If a dose is missed, take it as soon as remembered with food if within 30 minutes of a meal. However, if it is almost time for the next scheduled dose, skip the missed dose and resume the regular dosing schedule. Do not double the dose to make up for a missed administration. Consistent dosing with meals is important for effective phosphate control, so patients should try to maintain regular dosing patterns. If multiple doses are missed, contact the healthcare provider for guidance, as phosphorus levels may rise requiring additional monitoring or temporary dietary adjustments. Maintain a dosing diary if forgetfulness is a recurring issue.

Overdose

Overdose may lead to hypercalcemia, with symptoms including nausea, vomiting, anorexia, constipation, abdominal pain, dry mouth, thirst, polyuria, lethargy, confusion, and in severe cases, coma. Progressive hypercalcemia can lead to vascular and soft tissue calcification, nephrocalcinosis, and cardiac arrhythmias. Treatment involves immediate discontinuation of PhosLo, low calcium diet, and hydration with saline diuresis under medical supervision. Severe cases may require loop diuretics (after adequate hydration), bisphosphonates, calcitonin, or dialysis in renal patients. Serum calcium and phosphorus levels should be monitored frequently. Patients should seek immediate medical attention if overdose is suspected, especially if experiencing symptoms of severe hypercalcemia.

Storage

Store at controlled room temperature between 20°-25°C (68°-77°F), with excursions permitted between 15°-30°C (59°-86°F). Keep container tightly closed and protect from moisture and light. Store in the original container with the cap securely closed. Keep out of reach of children and pets. Do not transfer tablets to other containers unless specifically designed for medication storage. Do not use if the seal is broken or missing. Discard any medication that has expired or shows signs of deterioration (discoloration, unusual odor, or physical damage). Do not flush medications down the toilet or pour down the drain unless specifically instructed to do so.

Disclaimer

This information is for educational purposes only and does not constitute medical advice. PhosLo is a prescription medication that should be used only under the supervision of a qualified healthcare provider. Individual response to medication may vary, and only your healthcare provider can determine the appropriate treatment based on your specific medical condition, laboratory values, and overall health status. Never adjust dosage or discontinue medication without consulting your physician. Report any adverse effects or concerns to your healthcare provider promptly. The information provided here is not exhaustive and should not replace professional medical guidance.

Reviews

“After struggling with phosphorus control for years, PhosLo finally brought my levels into target range. The twice-daily dosing with meals integrates well with my dialysis schedule.” - Renal patient, 58

“My nephrologist switched me to PhosLo six months ago, and my calcium-phosphate product has remained stable without the calcium spikes I experienced with previous binders.” - ESRD patient, 64

“As a renal dietitian, I’ve observed consistent phosphorus reduction in patients using PhosLo when combined with appropriate dietary modifications. The predictable binding capacity helps in meal planning.” - Healthcare professional

“Initially experienced some constipation, but with dose adjustment and increased fluid intake, this side effect resolved while maintaining effective phosphorus control.” - Dialysis patient, 47

“After three months on PhosLo, my parathyroid hormone levels have decreased significantly, reducing the need for additional interventions.” - Chronic kidney disease patient, 52