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Sodium hyaluronate is the sodium salt of hyaluronan. The name hyaluronic acid is derived from the Greek word ύαλος (hyalos) meaning vitreous, and uronic acid as it was first isolated from the vitreous humour in the eye and possesses a high uronic acid content. The term hyaluronate also refers to the conjugate base of hyaluronic acid. Because the molecule typically exists in vivo in its polyanionic form, it is most commonly referred to as hyaluronan. It is a visco-elastic polymer normally found in the aqueous and vitreous humour.
Sodium hyaluronate is a viscous solution consisting of a high molecular weight (500,000-730,000 daltons) fraction of purified natural sodium hyaluronate in buffered physiological sodium chloride. Hyaluronic acid is a natural complex sugar of the glycosaminoglycan family and is a long-chain polymer containing repeating disaccharide units of Na-glucuronate-N-acetylglucosamine. Sodium hyaluronate occurs naturally on the corneal endothelium, bound to specific receptors for which it has a high affinity.
Chemically, sodium hyaluronate referred to as Sodium (2S,3S,4R,5R,6R)-3- [(2S,3R,4R,5S,6R)-3-acetamido-4-[(2R,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxyoxan-2-yl]oxy-5-hydroxy-6-(hydroxymethyl)oxan-2-yl]oxy-6-[(2R,3R,4R,5S,6R)-3-acetamido-2,5-dihydroxy-6-(hydroxymethyl)oxan-4-yl]oxy-4,5-dihydroxyoxane-2-carboxylic acid. It is produced by biological culture of genetic transformed bacteria.[unreliable source?]
Sodium hyaluronate is used as a viscosupplement, administered through a series of injections into the knee, increasing the viscosity of the synovial fluid, which helps lubricate, cushion and reduce pain in the joint. It is generally used as a last resort before surgery and provides symptomatic relief, by recovering the viscoelasticity of the articular fluid, and by stimulating new production from synovial fluid. Use of sodium hyaluronate may reduce the need for joint replacement. Injections appear to increase in effectiveness over the course of four weeks, reaching a peak at eight weeks and retaining some effectiveness at six months, with greater benefit for osteoarthritis than oral analgesics. It may also be effective when used with other joints.
Sodium hyaluronate may also be used in plastic surgery to reduce wrinkles on the face or as a filler in other parts of the body. It may be used in ophthalmology to assist in the extraction of cataracts, the implantation of intraocular lenses, corneal transplants, glaucoma filtration, retinal attachment and in the treatment of dry eyes.
Sodium hyaluronate is also used to coat the bladder lining in treating interstitial cystitis.
Sodium hyaluronate is contraindicated for people who are sensitive to hyaluronate preparations, or when there are infections or skin disease at the injection site.
Adverse effects are relatively rare when used to treat the joints.
Mechanism of action
Sodium hyaluronate functions as a tissue lubricant and is thought to play an important role in modulating the interactions between adjacent tissues. Sodium hyaluronate is a polysaccharide which is distributed widely in the extracellular matrix of connective tissue in man. It forms a viscoelastic solution in water which makes it suitable for aqueous and vitreous humor in ophthalmic surgery. Mechanical protection for tissues (iris, retina) and cell layers (corneal, endothelium, and epithelium) are provided by the high viscosity of the solution. Elasticity of the solution assists in absorbing mechanical stress and providing a protective buffer for tissues. This viscoelasticity enables maintenance of a deep chamber during surgical manipulation since the solution does not flow out of the open anterior chamber. In facilitating wound healing, it is thought that it acts as a protective transport vehicle, taking peptide growth factors and other structural proteins to a site of action. It is then enzymatically degraded and active proteins are released to promote tissue repair. Sodium hyaluronate is being used intra-articularly to treat osteoarthritis.
Physical and chemical properties
Sodium hyaluronate is absorbed and diffuses slowly out of the injection site. It is eliminated via the canal of Schlemm.
Sodium hyaluronate hyaluronan started to be in use to treat osteoarthritis of the knee in year 1986 with the product Hyalart/Hyalgan by Fidia of Italy, in intra-articular injections.
Brand names of Sodium hyaluronate in Market include (alphabetically):
- AMO Vitrax (ocular)
- AMVISIC Plus (ocular)
- CYSTISTAR, Healon (ocular)
- HYLO-COMOD (Eye Drop)
- EUFLEXXA, Bio Technology General (Israel)-Meditrina SA (Rx articular), Molecular weight: 2,400,000-3,600,000 Daltons
- GONILERT/Verisfield (UK) (Rx/articular). Molecular weight:1,800,000-2,000,000 Daltons
- HYALGAN/HYALART- Fidia (Italy)(Medical Device/Rx articular)
- MONOVISC- Anika (USA)(MedicalDevice/articular)
- OSTENIL- TRB Chemedica (Switzerland)(articular injection) 
- RECOSYN- Merckle Recordati (Germany) Recosyn info leaflet
- VISCURE- Cube (UK)(Rx/articular), Molecular weight:1,800,000-2,000,000 Daltons
- VISMED- TRB Chemedica (Switzerland)(eye drop)
- YARDEL- Libytec (Impfstoffwerk Dessau-Tornau/Germany,(Rx/articular), Molecular weight:1,800,000-2,000,000 Daltons
- Yardel/Libitec brochure 2011, page 4
- Puhl, W.; Scharf, P. (1997). "Intra-articular hyaluronan treatment for osteoarthritis". Annals of the rheumatic diseases 56 (7): 441. doi:10.1136/ard.56.7.441. PMC 1752402. PMID 9486013.
- Karlsson, J.; Sjögren, L. S.; Lohmander, L. S. (2002). "Comparison of two hyaluronan drugs and placebo in patients with knee osteoarthritis. A controlled, randomized, double-blind, parallel-design multicentre study". Rheumatology (Oxford, England) 41 (11): 1240–1248. PMID 12421996.
- Jubb, R. W.; Piva, S.; Beinat, L.; Dacre, J.; Gishen, P. (2003). "A one-year, randomised, placebo (saline) controlled clinical trial of 500-730 kDa sodium hyaluronate (Hyalgan) on the radiological change in osteoarthritis of the knee". International journal of clinical practice 57 (6): 467–474. PMID 12918884.
- Kotz, R.; Kolarz, G. (1999). "Intra-articular hyaluronic acid: Duration of effect and results of repeated treatment cycles". American journal of orthopedics (Belle Mead, N.J.) 28 (11 Suppl): 5–7. PMID 10587245.
- Bannuru, R. R.; Natov, N. S.; Dasi, U. R.; Schmid, C. H.; McAlindon, T. E. (2011). "Therapeutic trajectory following intra-articular hyaluronic acid injection in knee osteoarthritis – meta-analysis". Osteoarthritis and Cartilage 19 (6): 611–619. doi:10.1016/j.joca.2010.09.014. PMID 21443958.
- Salk, R. S.; Chang, T. J.; d'Costa, W. F.; Soomekh, D. J.; Grogan, K. A. (2006). "Sodium Hyaluronate in the Treatment of Osteoarthritis of the Ankle: A Controlled, Randomized, Double-Blind Pilot Study". The Journal of Bone and Joint Surgery 88 (2): 295–302. doi:10.2106/JBJS.E.00193. PMID 16452740.
- Beasley, K.; Weiss, M.; Weiss, R. (2009). "Hyaluronic Acid Fillers: A Comprehensive Review". Facial Plastic Surgery 25 (2): 086–094. doi:10.1055/s-0029-1220647. PMID 19415575.
- Shimmura, S.; Ono, M.; Shinozaki, K.; Toda, I.; Takamura, E.; Mashima, Y.; Tsubota, K. (1995). "Sodium hyaluronate eyedrops in the treatment of dry eyes". The British journal of ophthalmology 79 (11): 1007–1011. PMC 505317. PMID 8534643.
- Boucher, W. S.; Letourneau, R.; Huang, M.; Kempuraj, D.; Green, M.; Sant, G. R.; Theoharides, T. C. (2002). "Intravesical sodium hyaluronate inhibits the rat urinary mast cell mediator increase triggered by acute immobilization stress". The Journal of Urology 167 (1): 380–384. doi:10.1016/S0022-5347(05)65472-9. PMID 11743360.