Phosphate binders
Encyclopedia
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 with chronic renal failure
(CRF) as they cannot get rid of the phosphates that get into their blood (i.e. the serum phosphate in chronic renal failure is typically elevated).
phosphate
is important because it is associated with bone pathology and regulated together with serum calcium
by the parathyroid hormone
(PTH). High (serum) phosphate levels (known as hyperphosphatemia
) normally results in an elevation of the PTH level, which then leads to more phosphate excretion into the urine
. If the kidney
s do not function properly the phosphate level increases. Also, the serum calcium
levels tend to be low. This is because the kidneys in chronic renal failure do not produce the active form of vitamin 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 the bone
and, if it is not replaced, bone is lost. Bone loss and damage due to CRF is called renal osteodystrophy
. To avoid a high PTH and bone loss in patients with CRF, CRF patients typically avoid high phosphate intake and take calcium
supplements, vitamin D and phosphate binders.
, calcium, or lanthanum
salts) that react with phosphate and form an insoluble compound. Phosphate binders, such as sevelamer
, may also be polymer
ic structures which bind to phosphate and are then excreted.
) 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.
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...
and taken with meals and snacks. They are typically used in patients with chronic renal failure
Chronic renal failure
Chronic kidney disease , also known as chronic renal disease, is a progressive loss in renal function over a period of months or years. The symptoms of worsening kidney function are unspecific, and might include feeling generally unwell and experiencing a reduced appetite...
(CRF) as they cannot get rid of the phosphates that get into their blood (i.e. the serum phosphate in chronic renal failure is typically elevated).
Clinical use
For patients with chronic renal failure, controlling serumBlood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
phosphate
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...
is important because it is associated with bone pathology and regulated together with serum calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
by the parathyroid hormone
Parathyroid hormone
Parathyroid hormone , parathormone or parathyrin, is secreted by the chief cells of the parathyroid glands as a polypeptide containing 84 amino acids...
(PTH). High (serum) phosphate levels (known as hyperphosphatemia
Hyperphosphatemia
Hyperphosphatemia is an electrolyte disturbance in which there is an abnormally elevated level of phosphate in the blood. Often, calcium levels are lowered due to precipitation of phosphate with the calcium in tissues.-Signs and symptoms:...
) normally results in an elevation of the PTH level, which then leads to more phosphate excretion into the urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
. If the kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
s do not function properly the phosphate level increases. Also, the serum calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
levels tend to be low. This is because the kidneys in chronic renal failure do not produce the active form of vitamin D
Vitamin D
Vitamin D is a group of fat-soluble secosteroids. In humans, vitamin D is unique both because it functions as a prohormone and because the body can synthesize it when sun exposure is adequate ....
(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
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
from the bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
and, if it is not replaced, bone is lost. Bone loss and damage due to CRF is called renal osteodystrophy
Renal osteodystrophy
Renal osteodystrophy or chronic kidney disease-mineral and bone disorder is a bone pathology, characterized by bone mineralization deficiency, that is a direct result of the electrolyte and endocrine derangements that accompany chronic kidney disease...
. To avoid a high PTH and bone loss in patients with CRF, CRF patients typically avoid high phosphate intake and take calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
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 as aluminiumAluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
, calcium, or lanthanum
Lanthanum
Lanthanum is a chemical element with the symbol La and atomic number 57.Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table and is the first element of the lanthanide series. It is found in some rare-earth minerals, usually in combination with cerium and...
salts) that react with phosphate and form an insoluble compound. Phosphate binders, such as sevelamer
Sevelamer
Sevelamer is a phosphate binding drug used to prevent hyperphosphatemia in patients with chronic renal failure. When taken with meals, it binds to dietary phosphate and prevents its absorption...
, may also be polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
ic structures which bind to phosphate and are then excreted.
Adverse effects
With regard to phosphate binders, aluminium-containing compounds (such as aluminium hydroxideAluminium hydroxide
Aluminium hydroxide, Al3, ATH, sometimes erroneously called Hydrate of alumina, is found in nature as the mineral gibbsite and its three, much more rare forms, polymorphs: bayerite, doyleite and nordstrandite. Closely related are aluminium oxide hydroxide, AlO, and aluminium oxide, Al2O3,...
) are the least preferred because prolonged aluminium intake can cause encephalopathy
Encephalopathy
Encephalopathy means disorder or disease of the brain. In modern usage, encephalopathy does not refer to a single disease, but rather to a syndrome of global brain dysfunction; this syndrome can be caused by many different illnesses.-Terminology:...
and osteomalacia
Osteomalacia
Osteomalacia is the softening of the bones caused by defective bone mineralization secondary to inadequate amounts of available phosphorus and calcium, or because of overactive resorption of calcium from the bone as a result of hyperparathyroidism...
. If calcium is already being used as a supplement, additional calcium used as a phosphate binder may cause hypercalcemia and tissue-damaging calcinosis
Calcinosis
-Dystrophic calcification:The most common type of calcinosis is dystrophic calcification. This type of calcification can occur as a response to any soft tissue damage, including that involved in implantation of medical devices.-Metastatic calcification:...
. One may avoid these adverse effects by using phosphate binders that do not contain calcium or aluminium as active ingredients, such as lanthanum carbonate
Lanthanum carbonate
Lanthanum carbonate, La23, is the salt formed by lanthanum cations and carbonate anions. It is an ore of lanthanum metal, along with monazite.- Chemistry :...
or sevelamer.
Common phosphate binders
- Aluminium hydroxideAluminium hydroxideAluminium hydroxide, Al3, ATH, sometimes erroneously called Hydrate of alumina, is found in nature as the mineral gibbsite and its three, much more rare forms, polymorphs: bayerite, doyleite and nordstrandite. Closely related are aluminium oxide hydroxide, AlO, and aluminium oxide, Al2O3,...
(Alucaps) - Calcium carbonateCalcium carbonateCalcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...
(Calcichew, Titralac) - Calcium acetateCalcium acetateThe chemical compound calcium acetate is the calcium salt of acetic acid. It has the formula Ca2. Its standard name is calcium acetate, while calcium ethanoate is the systematic IUPAC name. An older name is acetate of lime...
(Phosex, PhosLo) - Lanthanum carbonateLanthanum carbonateLanthanum carbonate, La23, is the salt formed by lanthanum cations and carbonate anions. It is an ore of lanthanum metal, along with monazite.- Chemistry :...
(Fosrenol) - SevelamerSevelamerSevelamer is a phosphate binding drug used to prevent hyperphosphatemia in patients with chronic renal failure. When taken with meals, it binds to dietary phosphate and prevents its absorption...
(Renagel, Renvela) - Calcium acetate/magnesium carbonateCalcium acetate/magnesium carbonateCalcium acetate/magnesium carbonate is a fixed-dose combination drug that contains 110 mg calcium and 60 mg magnesium indicated as a phosphate binder for dialysis patients suffering from hyperphosphataemia...
(Renepho, OsvaRen)
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 - Phophorus Control - Information for healthcare professionals on the treatment and management of hyperphosphatemia