Description

Sevelamer hydrochloride is a non-absorbable phosphate binder. It is a polymer of polyallylamine hydrochloride, which is a cationic (positively charged) resin. Sevelamer is not metabolized or absorbed from the gastrointestinal tract and is a metal-free and calcium-free alternative to other phosphate binders. It is administered orally, typically in tablet or powder form, to be taken with meals.

Indication

Sevelamer hydrochloride is indicated for the control of serum phosphorus (phosphate) levels in adult and pediatric patients with chronic kidney disease (CKD) who are on dialysis. Its primary purpose is to manage hyperphosphatemia, a common and serious complication of CKD. While its primary indication is for dialysis patients, it may also be used in patients with CKD who are not yet on dialysis, where elevated phosphorus levels are a concern.

Mechanism of Action

The mechanism of action of Sevelamer hydrochloride is entirely localized to the gastrointestinal tract. It works by preventing the absorption of dietary phosphate. The process is as follows:

1. Cationic Polymer: Sevelamer is a long-chain polymer with numerous amine groups. At physiological pH in the gastrointestinal tract, these amine groups become positively charged.
2. Phosphate Binding: Phosphate ions (PO43−​) from food are negatively charged. As food moves through the digestive system, the positively charged amine groups on the sevelamer molecule are able to bind to the negatively charged phosphate ions.
3. Insoluble Complex Formation: This binding forms a stable, insoluble complex between the sevelamer and the phosphate.
4. Elimination in Feces: Because the complex is insoluble and sevelamer itself is not absorbed, the entire complex is excreted from the body in the feces.

5. Reduced Phosphorus Absorption: By binding to dietary phosphate and preventing its absorption, sevelamer effectively lowers the amount of phosphorus that enters the bloodstream. This helps to reduce high serum phosphorus levels (hyperphosphatemia), which is crucial for preventing serious complications associated with CKD, such as renal bone disease and cardiovascular calcification.