Etidronic acid
Encyclopedia
Etidronic acid or 1-hydroxyethane 1,1-diphosphonic acid (HEDP) is a bisphosphonate
Bisphosphonate
Bisphosphonates are a class of drugs that prevent the loss of bone mass, used to treat osteoporosis and similar diseases...

 used in detergents, water treatment, cosmetics and pharmaceutical treatment.

An etidronate is a salt of etidronic acid, abbeviated MnHEDP (M: is a cation, n: number of M maximum 4).

Chelating Agent and Anti-oxidant

Etidronic acid is a chelating agent and may be added to bind or, to some extent, counter the effects of substances, such as 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...

, iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 or other metal ions, which may be discharged as a component of grey wastewater and could conceivably contaminate groundwater supplies. As a phosphonate it has corrosion
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...

 inhibiting properties on unnalloyed steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

. Etidronic acid also acts to retard rancidification and oxidation of fatty acids.

HEDP and its salts are added to detergent
Detergent
A detergent is a surfactant or a mixture of surfactants with "cleaning properties in dilute solutions." In common usage, "detergent" refers to alkylbenzenesulfonates, a family of compounds that are similar to soap but are less affected by hard water...

s and other cleaning agents to prevent the effects of hard water
Hard water
Hard water is water that has high mineral content . Hard water has high concentrations of Ca2+ and Mg2+ ions. Hard water is generally not harmful to one's health but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling...

. It is also used in peroxide
Peroxide
A peroxide is a compound containing an oxygen–oxygen single bond or the peroxide anion .The O−O group is called the peroxide group or peroxo group. In contrast to oxide ions, the oxygen atoms in the peroxide ion have an oxidation state of −1.The simplest stable peroxide is hydrogen peroxide...

 bleaching to prevent degradation of peroxides by transition metals.

Etidronic acid is listed as an ingredient of several cosmetic formulations where it is used for suppressing radical
Radical (chemistry)
Radicals are atoms, molecules, or ions with unpaired electrons on an open shell configuration. Free radicals may have positive, negative, or zero charge...

 formation, emulsion
Emulsion
An emulsion is a mixture of two or more liquids that are normally immiscible . Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion is used when both the dispersed and the...

 stabilser and viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

 control. While etidronic acid has not been limited from inclusion in cosmetics and does have legitimate uses, it is recommended that, as with most cosmetic products (particularly soaps), the product should be thoroughly rinsed from the skin after use.

Etidronic acid is also included among swimming pool chemicals. It is used as a stain inhibitor to prevent metal ions coming out of solution and staining the sides of swimming pools.

Pharmaceutical

Etidronic acid (trade name Didronel) is a bisphosphonate used to strengthen 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...

, treat osteoporosis
Osteoporosis
Osteoporosis is a disease of bones that leads to an increased risk of fracture. In osteoporosis the bone mineral density is reduced, bone microarchitecture is deteriorating, and the amount and variety of proteins in bone is altered...

, and treat Paget's disease of bone
Paget's disease of bone
Paget's disease is a chronic disorder that can result in enlarged and misshapen bones. The excessive breakdown and formation of bone tissue causes affected bone to weaken, resulting in pain, misshapen bones, fractures, and arthritis in the joints near the affected bones...

.

Bisphosphonates primarily reduce osteoclast
Osteoclast
An osteoclast is a type of bone cell that removes bone tissue by removing its mineralized matrix and breaking up the organic bone . This process is known as bone resorption. Osteoclasts were discovered by Kolliker in 1873...

ic activity, which prevents bone resorption
Bone resorption
Bone resorption is the process by which osteoclasts break down bone and release the minerals, resulting in a transfer of calcium from bone fluid to the blood....

, and thus moves the bone resorption/formation equilibrium toward the formation side and hence makes bone stronger on the long run. Etidronate, unlike other bisphosphonates, also prevents bone calcification
Calcification
Calcification is the process in which calcium salts build up in soft tissue, causing it to harden. Calcifications may be classified on whether there is mineral balance or not, and the location of the calcification.-Causes:...

. For this reason, other bisphosphonates, like alendronate
Alendronate
Alendronic acid or alendronate sodium — sold as Fosamax by Merck — is a bisphosphonate drug used for osteoporosis and several other bone diseases. It is marketed alone as well as in combination with vitamin D . Merck's U.S...

, are preferred when fighting osteoporosis. To prevent bone resorption without affecting too much bone calcification, etidronate must be administered only for a short time once in a while, for example for two weeks every 3 months. When given on a continuous basis, say every day, etidronate will altogether prevent bone calcification. This effect may be useful and etidronate is in fact used this way to fight heterotopic ossification
Heterotopic ossification
Heterotopic ossification is the process by which bone tissue forms outside of the skeleton.-Diagnosis:During the early stage, an x-ray will not be helpful because there is no calcium in the matrix...

. But in the long run, if used on a continuous basis, it will cause 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...

.
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