Sevelamer is a medication prescribed to help manage elevated phosphate levels in the bloodstream, a condition frequently observed in individuals with chronic kidney disease (CKD), particularly those undergoing dialysis. This medication works to bind excess dietary phosphate, preventing its absorption into the body. By controlling phosphate levels, sevelamer helps to mitigate various health complications associated with kidney disease.
Understanding Sevelamer’s Role
Individuals with advanced kidney disease often develop hyperphosphatemia, characterized by high levels of phosphate in the blood. Healthy kidneys efficiently remove excess phosphate, but impaired kidney function leads to its accumulation. This buildup can cause serious health problems.
Ectopic calcification, where calcium and phosphate form mineral deposits in soft tissues and blood vessels, can contribute to cardiovascular issues like hardening of the arteries, increasing the risk of heart disease and stroke. Elevated phosphate also contributes to secondary hyperparathyroidism, where parathyroid glands produce excess parathyroid hormone (PTH). This can lead to bone disease, weakening bones and increasing fracture risk. Sevelamer addresses these concerns by binding dietary phosphate in the digestive tract, forming an insoluble complex that is excreted in feces, reducing absorption into the bloodstream.
How Sevelamer Dosage is Determined and Managed
Sevelamer dosage is individualized and determined by a healthcare provider based on a patient’s serum phosphate levels. The goal is to lower serum phosphorus to a target range, typically 3.5 to 5.5 mg/dL. Regular blood tests monitor phosphate levels, guiding medication adjustments.
Typical starting dosages for sevelamer, whether sevelamer carbonate (Renvela) or sevelamer hydrochloride (Renagel), range from 800 mg to 1600 mg, taken three times daily with meals. For instance, if serum phosphorus is between 5.5 and 7.5 mg/dL, an initial dose might be 800 mg three times daily. If levels are 7.5 mg/dL or higher, a starting dose of 1600 mg three times daily may be considered.
Dose adjustments are made in increments of 400 mg to 800 mg per meal, at two-week intervals, until desired serum phosphate levels are achieved. The average daily dose for adults is approximately 7.2 grams, with a maximum of 14 grams. Taking sevelamer with meals is essential to bind dietary phosphate and prevent its absorption.
Sevelamer is available in different forms, including tablets and powder for oral suspension. The powder can be mixed with water; for example, an 800 mg packet requires 30 mL of water, and a 2400 mg packet needs 60 mL, to be stirred vigorously and consumed within 30 minutes. While both sevelamer carbonate and sevelamer hydrochloride work similarly, sevelamer carbonate may be preferred in some cases due to a reduced risk of worsening metabolic acidosis.
Important Considerations for Patients
Patients taking sevelamer may experience common side effects, primarily gastrointestinal. These can include nausea, vomiting, diarrhea, constipation, abdominal pain, gas, and dyspepsia. Less common side effects include tiredness, itching, and joint pain. Patients should contact their healthcare provider if symptoms are severe or persistent.
Patients should inform their doctor about constipation, a common side effect, as severe cases could lead to complications like bowel obstruction. Sevelamer can interfere with the absorption of fat-soluble vitamins (A, D, E, K) and folic acid, so supplements may be recommended.
If a dose of sevelamer is missed, patients should skip the missed dose and take the next dose at the regularly scheduled time with their next meal. Do not take a double dose to compensate. Sevelamer can interact with other medications by reducing their absorption, so other oral medications are often advised to be taken at least one hour before or three hours after sevelamer. For example, ciprofloxacin and mycophenolate mofetil require specific timing adjustments. Adherence to the prescribed regimen and regular follow-up appointments for monitoring blood phosphate levels and overall health are important.