|Systematic (IUPAC) name|
|Trade names||Avagard, BactoShield CHG, Betasept, ChloraPrep, Chlorostat, Dyna-Hex, Hibiclens, Hibistat, Operand Chlorhexidine Gluconate, Peridex, PerioChip, PerioGard|
|Legal status||OTC (US)|
|ATC code||A01 B05, D08, D09 (dressing), R02, S01, S02, S03|
|Mol. mass||505.446 g/mol|
|Solubility in water||0.0008 mg/mL (20 °C)|
|(what is this?)|
Chlorhexidine is a cationic polybiguanide (bisbiguanide). It is used primarily as its salts (e.g., the dihydrochloride, diacetate and digluconate).
Chlorhexidine is used in disinfectants (disinfection of the skin and hands), cosmetics (additive to creams, toothpaste, deodorants, and antiperspirants), and pharmaceutical products (preservative in eye drops, active substance in wound dressings and antiseptic mouthwashes). 
At physiologic pH, chlorhexidine salts dissociate and release the positively charged chlorhexidine cation. The bactericidal effect is a result of the binding of this cationic molecule to negatively charged bacterial cell walls. At low concentrations of chlorhexidine, this results in a bacteriostatic effect; at high concentrations, membrane disruption results in cell death.
Chlorhexidine is active against gram-positive and gram-negative organisms, facultative anaerobes, aerobes, and yeast. It is particularly effective against gram-positive bacteria (in concentrations ≥ 1 µg/L). Significantly higher concentrations (10 to more than 73 μg/mL) are required for gram-negative bacteria and fungi. In the presence of blood or protein the efficacy is reduced by a factor of 100 to 1000. Chlorhexidine is ineffective against polioviruses and adenoviruses. The effectiveness against herpes viruses has not yet been established unequivocally. 
Chlorhexidine, like other cation-active compounds, remains on the skin. It is frequently combined with alcohols (ethanol and isopropyl alcohol).
Chlorhexidine is often used as an active ingredient in mouthwash designed to reduce dental plaque and oral bacteria. It has been shown to have an immediate bactericidal action and a prolonged bacteriostatic action due to adsorption onto the pellicle-coated enamel surface. If it is not deactivated, chlorhexidine lasts longer in the mouth than other mouthwashes and this is partly why it is to be preferred over other treatments for gingivitis. To treat periodontal pockets equal or greater than 5mm; chlorhexidine is also available in high concentration (36%) in a gelatine-chip.
There are oral pathologic conditions in which the maintenance of oral hygiene with the twice-daily use with 0.12% chlorhexidine gluconate solution (in which a salt of chlorhexidine and gluconic acid has been dissolved) is required for healing and regeneration of the oral tissues. These conditions included gingivitis, periodontitis, dental traumas (such as subluxation), oral cysts, and after wisdom tooth extraction. The clinical efficacy of the application of chlorhexidine as a component of oral rinses is well documented by many clinical studies that are summarized by review articles.
Continued use of products containing chlorhexidine for long periods can cause stains on teeth, tongue, and gingiva, also on silicate and resin restorations; prolonged use can also reduce bitter and salty taste sensations - this latter symptom can be reversed by ceasing use of chlorhexidine. The brownish discoloration of teeth and tongue are due to the fact that the disintegration of bacterial membranes leads to the denaturation of bacterial proteins. At the same time, disulfide functions are reduced to thiol functions that form dark complexes with iron(III) ions found in saliva.
According to the prescribing information, chlorhexidine gluconate has not been proven to reduce subgingival calculus and in some studies actually increased deposits. When combined with xylitol, a synergistic effect has been observed to enhance efficacy.
Chlorhexidine is neutralized by common toothpaste additives such as sodium lauryl sulfate (SLS) and sodium monofluorophosphate (MFP). Although data are limited, to maximize effectiveness it may be best to keep a 30-minute to 2-hour interval between brushing and using the mouthwash.
Chlorhexidine gluconate is used as a skin cleanser for surgical scrub, cleanser for skin wounds, preoperative skin preparation and germicidal hand rinse.
Chlorhexidine does not meet current European specifications for a hand disinfectant. Under the test conditions of the European Standard EN 1499 there was no significant difference in the efficacy between a 4 % solution of chlorhexidine digluconate and soap.
Use in animals
For use in animals, it is used as a topical disinfectant of wounds. Some common brand names are ChlorhexiDerm, ResiChlor, Savinox plus (Bioshields), Germi-STAT Antimicrobial Skin Cleanser, Nolvasan Skin and Wound Cleaner, and Nolvasan Ointment. It is also more beneficial to wound healing than using saline solutions alone. Problems including deafness have been associated with the use of chlorhexidine products in cats. It is commonly used to manage skin infections in dogs. In addition to this it is an active ingredient in teat disinfectant products used within the dairy farming industry.
Chlorhexidine is deactivated by forming insoluble salts with anionic compounds, including the anionic surfactants commonly used as detergents in toothpastes and mouthwashes, anionic thickeners such as carbomer, and anionic emulsifiers such as acrylates/C10-30 alkyl acrylate crosspolymer, among many others. For this reason, chlorhexidine mouth rinses should be used at least 30 minutes after other dental products. For best effectiveness, food, drink, smoking, and mouth rinses should be avoided for at least one hour after use. Many topical skin products, cleansers, and hand sanitizers should also be avoided to prevent deactivation when chlorhexidine (a topical itself or the residue from a cleanser) is meant to remain on the skin.
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