Phosblock

Uses

Phosblock Hydrochloride is used for the reduction of serum phosphorus in patients with end-stage renal disease (ESRD).

Phosblock is also used to associated treatment for these conditions: Hyperphosphataemia

How Phosblock works

Phosblock prevents hyperphosphatemia by binding to dietary phosphate in the gut, preventing its absorption and thus decreasing serum parathyroid hormone levels.

Dosage

Phosblock dosage

Patients not taking a Phosphate Binder: The recommended starting dose of Phosblock is 800 to 1600 mg, which can be administered as two to four 400 mg Phosblock tablets, with meals based on serum phosphorus level. Renophos 400 Recommendation for the patients with hyperphosphatemia is given below-

Starting dose of Renophos for dialysis patients not taking any phosphate binder:

• Serum Phosphorus >5.5 and <7.5 mg/dL: 800 mg (2 tablets) three times daily with meals
• Serum Phosphorus ≥7.5 and <9.0 mg/dL: 1200 mg (3 tablets) three times daily with meals
• Serum Phosphorus ≥9.0 mg/dL: 1600 mg (4 tablets) three times daily with meals

Starting dose for dialysis patients switching from calcium acetate to Phosblock:

• Calcium Acetate 667 mg (1 tablet): Phosblock 800 mg (2 tablets)
• Calcium Acetate 1334 mg (2 tablets): Phosblock 1200 mg (3 tablets)
• Calcium Acetate 2001 mg (3 tablets): Phosblock 2000 mg (5 tablets)

Dose titration guideline:

• Serum Phosphorus >5.5 mg/dL: Increase 400 mg (1 tablet) per meal at 2 week intervals
• Serum Phosphorus 3.5-5.5 mg/dL: Maintain current dose
• Serum Phosphorus <3.5 mg/dL: Decrease 400 mg (1 tablet) per meal

Dose titration for all patients taking Phosblock: Dosage should be adjusted based on the serum phosphorus concentration with a goal of lowering serum phosphorus to 5.5 mg/dl or less. The dose may be increased or decreased by one tablet per meal at two week intervals as necessary.

Side Effects

Phosblock may cause dyspepsia, peritonitis, diarrhea, nausea, constipation, pruritus, abdominal distension, vomiting, fatigue, anorexia, arthralgia and less commonly ileus, bowel obstruction and bowel perforation.

Toxicity

Phosblock has been given to normal healthy volunteers in doses of up to 14 grams per day for eight days with no adverse effects. Phosblock has been given in average doses up to 13 grams per day to hemodialysis patients. There are no reported overdosages of sevelamer in patients. Since sevelamer is not absorbed, the risk of systemic toxicity is low.

Precaution

The safety and efficacy of Phosblock in patients with dysphagia, swallowing disorders, severe GI motility disorders including severe constipation, or major GI tract surgery have not been established. Caution should be exercised when Phosblock is used in patients with these GI disorders.

Interaction

Phosblock has been studied in human drug-drug interaction studies with ciprofloxacin, digoxin, warfarin, enalapril, metoprolol and iron.

Food Interaction

• Take with food.

[Moderate] ADJUST DOSING INTERVAL: Phosblock may decrease the oral bioavailability of concomitantly administered drugs. While clinical data are lacking for most drugs, the intestinal absorption of some may be impaired due to sevelamer's binding capabilities.

MANAGEMENT: As a precaution, drugs that can be adversely affected by alterations in blood levels should be administered 1 hour before or 3 hours after sevelamer.

Phosblock multivitamins interaction

[Moderate] ADJUST DOSING INTERVAL: Bile acid sequestrants and the phosphate binder, sevelamer, can decrease the absorption of fat-soluble vitamins A, D, E, and K.

In non-clinical safety studies, rats administered colesevelam at doses greater than 30-fold the projected human clinical dose developed hemorrhage in association with vitamin K deficiency.

In a crossover study involving healthy subjects, coadministration of sevelamer with calcitriol resulted in a significant reduction in bioavailability for calcitriol (calcitriol with sevelamer vs calcitriol alone: AUC 137 pg*h
Oral vitamin supplements should be administered at least 4 hours before colesevelam and either 1 hour before or 4 to 6 hours after other bile acid sequestrants and sevelamer.

Phosblock Drug Interaction

Moderate: multivitamin with iron, multivitamin, levothyroxine, cholecalciferolUnknown: aspirin, aspirin, docusate, apixaban, epoetin alfa, omega-3 polyunsaturated fatty acids, insulin glargine, insulin glargine, furosemide, metoprolol, metoprolol, polyethylene glycol 3350, insulin aspart, cinacalcet, acetaminophen, ondansetron

Phosblock Disease Interaction

Major: gastrointestinal diseaseModerate: dysphagia, renal disease

Elimination Route

Not absorbed following oral administration, however no absorption studies have been performed in patients with renal disease. Phosblock may bind to dietary phosphates and prevent its gastrointestinal absorption when sevelamer is administered in combination with food.

Pregnancy & Breastfeeding use

Pregnancy Category C. No adequate and controlled studies have been conducted using Phosblock in nursing mothers. Phosblock should be used during breastfeeding only if the potential benefit justifies the potential risks.

Contraindication

Phosblock is contraindicated in patients with hypophosphatemia or bowel obstruction and in patients with known hypersensitivity to Phosblock hydrochloride or any of its constituents.

Acute Overdose

Over dosages of Phosblock in patients was never reported. Since Phosblock is not absorbed, the risk of systemic toxicity is low.

Innovators Monograph

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