User:PharmD2026/Phosphate binder

Mechanism of action
These agents work by binding to phosphate in the GI tract, thereby making it unavailable to the body for absorption. Hence, these drugs are usually taken with meals to bind any phosphate that may be present in the ingested food. Phosphate binders may be simple molecular entities (such as magnesium, aluminium, calcium, or lanthanum salts) that react with phosphate and form an insoluble compound. Phosphate binders such as sevelamer may also be polymeric structures which bind to phosphate and are then excreted.

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Calcium carbonate

Calcium-based phosphate binders, such as calcium carbonate, directly decrease phosphate levels by creating insoluble calcium-phosphate complexes which gets eliminated in the feces.

Lanthanum carbonate

Non-calcium-based phosphate binders, including lanthanum carbonate, form insoluble complexes with phosphates in your food; thereby reducing phosphate levels in the body.

Sevelamer carbonate

Sevelamer is an insoluble polymeric amine, which is protonated once in the intestines & this allows it to bind dietary phosphate. Phosphates are eliminated along with sevelamer, leading to a decrease in the body's phosphate levels.

Medical use
For people with chronic kidney failure, controlling serum phosphate is important because it is associated with bone pathology and regulated together with serum calcium by the parathyroid hormone (PTH).

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- Hypoparathyroidism is when PTH conc is very low & leads to hypocalcemia. The goal of clinical management of hypoparathyroidism is to correct acute & chronic hypocalcemia. The tx cornerstones of chronic hypoparathyroidism are oral supplementation of calcium and/or vit D, that can be associated w/ dietary restriction of sodium & phosphates, thiazide diuretics, & phosphate binders

- Relationship b/w PTH & Ca2+ is inversely proportional - low Ca2+ levels stimulate PTH secretion

- There's NO data available on the use of phosphate binders in hypoparathyroidism; therefore, phosphate binders should be used cautiously, & only if severe hyperphosphatemia is present

- A low-phosphate diet is recommended, & phosphate binders are rarely needed

- Phosphate binders are generally not used unless severe hyperphosphatemia

Adverse effects
With regard to phosphate binders, aluminium-containing compounds (such as aluminium hydroxide) are the least preferred because prolonged aluminium intake can cause encephalopathy and osteomalacia. If calcium is already being used as a supplement, additional calcium used as a phosphate binder may cause hypercalcemia and tissue-damaging calcinosis. One may avoid these adverse effects by using phosphate binders that do not contain calcium or aluminium as active ingredients, such as lanthanum carbonate or sevelamer.

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Calcium carbonate

- GI effects (nausea, vomiting, constipation)

- Risk of cardiovascular calcification

- Risk of hypercalcemia

Lanthanum carbonate

- GI obstruction

- Bile duct obstruction

- Hepatic impairment

- No hypercalcemia risk

Sevelamer carbonate

- GI effects (nausea, vomiting, constipation, flatulence)

- No hypercalcemia risk