# Phosphate binder

Phosphate binders are medications used to reduce the absorption of dietary phosphate; they are taken along with meals and snacks. They are frequently used in people with chronic kidney failure (CKF), who are less able to excrete phosphate, resulting in an elevated serum phosphate.

## 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.
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 food, thereby reducing the amount of phosphate in the body.
Sevelamer carbonate
Sevelamer is an insoluble polymeric amine, which is protonated once in the intestines and 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).

## Adverse effects

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

## Choice of agent

There have been limited trials comparing phosphate binders to placebo in the treatment of hyperphosphatemia in people with chronic kidney disease. When compared with people receiving calcium-based binders, people taking sevelamer have a reduced all-cause mortality.

### Types

Summary of Common Oral Phosphate Binders :
| Phosphate Binder | Brands | Advantages | Disadvantages |
| Aluminum salts | Alucaps | Calcium free | Risk of aluminum toxicity |
| | Basaljel | High binder efficiency regardless of pH | Requires frequent monitoring-extra cost |
| | | Cheap | |
| | | Moderate tablet burden | |
| Calcium carbonate | Calcichew | Aluminum free | Calcium containing-potential risk of hypercalcemia and ectopic calcification |
| | Titralac | Moderate binding efficacy | Parathyroid hormone oversuppression |
| | | Relatively low cost | Gastrointestinal side effects |
| | | Moderate tablet burden | Efficacy pH dependent |
| | | Chewable | |
| Calcium acetate | Lenal Ace | Aluminum free | Calcium containing-potential risk of hypercalcemia and ectopic calcification |
| | PhosLo | Higher efficacy than calcichew/sevelamer | Parathyroid hormone oversuppression |
| | | Moderately cheap | Gastrointestinal side effects |
| | | Lower calcium load than calcium carbonate | Large tablets & capsules, nonchewable formulation |
| Sevelamer hydrochloride/Sevelamer carbonate | Renagel | Aluminium and calcium free | Relatively costly |
| | Renvela | No gastrointestinal absorption | High pill burden |
| | | Moderate efficacy | Large tablets, nonchewable formulation |
| | | Reduces total and low-density lipoprotein cholesterol | Gastrointestinal side effects |
| | | | Binds fat-soluble vitamins |
| Lanthanum carbonate | Fosrenol | Aluminum and calcium free | Relatively costly |
| | | Minimal gastrointestinal absorption | Gastrointestinal side effects |
| | | High efficacy across full pH range | Larger tablet size may cause choking if not chewed well |
| | | Chewable formulation | |
| | | Palatable | |
| | | Low tablet burden | |
| Ferric Citrate | Auryxia | Iron based | Very costly |
| | | | Tablets can be toxic to young children |
| | | | Stool discoloration - may turn them black, obscuring intestinal bleeding |
* Calcium acetate/magnesium carbonate