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 BindersBurtis, C.A.; Ashwood, E.R. and Bruns, D.E. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 5th Edition. Elsevier. pp1552 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 CitrateAuryxiaIron basedVery costlyTablets can be toxic to young childrenStool discoloration - may turn them black, obscuring intestinal bleeding Calcium acetate/magnesium carbonate
References
Lederer E, Ouseph R, Erbeck K. Hyperphosphatemia, eMedicine.com, URL: Hyperphosphatemia: Practice Essentials, Background, Pathophysiology, Accessed on July 14, 2005.
External links High Phosphate Control - Official Fosrenol Homepage Phosphate Binders: What Are They And How Do They Work? - American Association of Kidney Patients* Phosphate Binders - National Kidney Foundation Phosphate Binders - Northwest Kidney Centers - a center that provides services for people with ESRD in the Seattle area. High Phosphate - Phosphorus Control - Information for healthcare professionals on the treatment and management of hyperphosphatemia
Common Phosphate Binders
Lanthanum - medlineplus.org Sevelamer - medlineplus.org Sevelamer - Renvela.com