- Phosphate binders
Phosphate binders are a group of medications used to reduce the absorption of
phosphate and taken with meals and snacks. They are typically used in patients withchronic renal failure (CRF) as they cannot get rid of the phosphate that gets into their blood (i.e. the serum phosphate in chronic renal failure is typically elevated).Clinical use
For patients with chronic renal failure, controlling serum
phosphate is important because it is associated with bone pathology and regulated together with serumcalcium by theparathyroid hormone (PTH). High (serum) phosphate levels (known ashyperphosphatemia ) normally results in an elevation of the PTH level, which then leads to more phosphate excretion into theurine .ref|Lederer If thekidney s do not function properly the phosphate level increases. Also, the serumcalcium levels tend to be low. This is because the kidneys in chronic renal failure do not produce the active form ofvitamin D (1,25-dihydroxycholecalciferol), which is important for calcium absorption from food. Low serum calcium levels, like high phosphate, also lead to a high PTH.A high PTH leads to a large mobilization of
calcium from thebone and, if it is not replaced, bone is lost. Bone loss and damage due to CRF is calledrenal osteodystrophy . To avoid a high PTH and bone loss in patients with CRF, CRF patients typically avoid high phosphate intake and takecalcium supplements, vitamin D and phosphate binders.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 asaluminium , calcium, orlanthanum salts) that react with phosphate and form aninsoluble compound. Phosphate binders, such assevelamer , may also bepolymer ic structures which bind to phosphate and are then excreted.Adverse effects
With regard to phosphate binders, aluminium-containing compounds (such as
aluminium hydroxide ) are the least preferred because prolonged aluminium intake can causeencephalopathy andosteomalacia . If calcium is already being used as a supplement, additional calcium used as a phosphate binder may causehypercalcemia and tissue-damagingcalcinosis . One may avoid these adverse effects by using phosphate binders that do not contain calcium or aluminium as active ingredients, such aslanthanum carbonate or sevelamer.Common phosphate binders
*
Aluminium hydroxide (Alucaps)
*Calcium carbonate (Calcichew, Titralac)
*Calcium acetate (Phosex, PhosLo)
*Lanthanum carbonate (Fosrenol)
*Sevelamer (Renagel, Renvela)References
# Lederer E, Ouseph R, Erbeck K. Hyperphosphatemia, eMedicine.com, URL: http://www.emedicine.com/med/topic1097.htm, Accessed on July 14, 2005.
External links
* [http://www.fosrenol.com/Consumers/Default.aspx High Phosphate Control - Official Fosrenol Homepage] *
* [http://www.aakp.org/AAKP/RenalifeArt/2001/phosphatebinders.htm Phosphate Binders: What Are They And How Do They Work?] - American Association of Kidney Patients*
* [http://www.kidney.org.uk/Medical-Info/drugs/phosinf.html Phosphate Binders] - National Kidney Foundation
* [http://www.nwkidney.org/images/website/docs/nutrition/phosphate.htm Phosphate Binders] - Northwest Kidney Centers - a center that provides services for people with ESRD in theSeattle area.
* [http://www.phosphoruscontrol.com/Default.aspx High Phosphate - Phophorus Control] - Information for healthcare professionals on the treatment and management of hyperphosphatemiaCommon Phosphate Binders (Generic)
* [http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a605015.html Lanthanum] - medlineplus.org
* [http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a601248.html Sevelamer] - medlineplus.org
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