Chlorhexidine antimicrobial activity

The optimum pH for chlorhexidine antimicrobial activity is in the range 5.5—7.0 but varies with the buffer used and the organism, having a range of pH 5—8. With S. aureus and E. coli, activity increases with increased pH the reverse occurs with P. aeruginosa. 

As is apparent from the above information, there is no ideal disinfectant, antiseptic or preservative. All chemical agents have their limitations either in terms of their antimicrobial activity, resistance to organic matter, stability, incompatibility, irritancy, toxicity or corrosivity. To overcome the limitations of an individual agent, formulations consisting of combinations of agents are available. For example, ethanol has been combined with chlorhexidine and iodine to produce more active preparations. The combination of chlorhexidine and cetrimide is also considered to improve activity. QACs and phenols have been combined with glutaraldehyde so that the same effect can be achieved with lower, less irritant concentrations of glutaraldehyde. Some... 

The most widely used and effective disinfectant solutions are based on iodine (iodophor) with concentrations ranging between 0.05% and 0.1%, but sometimes higher concentrations are recommended. Other agents such as chlorhexidine or chlorine dioxide, peroxide, sodium chloride and lactic acid may also be effective (Wilson et al., 1997) but are not common. Recent trials show positive effects of aloe vera-based dipping agents (Leon et al., 2004). One problem of iodine containing products is their low pH value (<4.0), which is necessary for their antimicrobial activity (Hansen and Hamann, 2003). 

Groppo FC, Famacciato JC, Simoes RP, et al. Antimicrobial activity of garlic, tea tree oil and chlorhexidine against oral microorganisms. Int Dent J 2002 52 433 137. 

Ultimately, the purpose of this in vitro study was to determine if the addition of 0.12% chlorhexidine would enhance the antimicrobial activity of GEMOSIL, and to comptire the antimicrobial activity to the widely used material MTA. 

Chlorhexidine is the most poteat oral antimicrobial agent available. It has side effects and is sold only with a prescription. It is active deflvered from a riase, but a compatible toothpaste vehicle for chlorhexidine has yet to be developed. 

Examples of preservatives are phenylmercuric nitrate or acetate (0.002% w/v), chlorhexidine acetate (0.01 % w/v), thiomersal (0.01 % w/v) and benzalkorrium chloride (0.01 % w/v). Chlorocresol is too toxic to the comeal epithehum, but 8-hydroxyquinoline and thiomersal may be used in specific instances. The principal considerahon in relation to antimicrobial properties is the activity of the bactericide against Pseudomonas aeruginosa, a major source of serious nosocomial eye infections. Although benzal-konium chloride is probably the most active of the recommended preservatives, it cannot always be used because of its incompatibility with many compounds commonly used to treat eye diseases, nor should it be used to preserve eye-drops containing anaesthetics. Since benzalkonium chloride reacts with natural mbber, silicone or butyl rabber teats should be substituted. Since silicone mbber is permeable to water vapour, products should not be stored for more than 3 months after manufacture. As with all mbber components, the mbber teat should be pre-equilibrated with the preservative prior to... 

Ethyl alcohol or isopropyl alcohol in an aqueous solution (between 70 and 92%) is an inexpensive and easily accessible disinfectant, which is rapidly acting and bactericidal as well as germicidal to most viruses, fungi, and other pathogens.13 However, its residual activity is limited and it should be used in conjunction with a longer-acting disinfectant (i.e., chlorhexidine) for optimal antimicrobial... 

An active ingredient not described by the TFM (Table 3) should be assessed for safety and efficacy under an investigational new dmg (MD) application and all pivotal studies submitted to the agency for review as an NDA. An example is the bisguanide class of antimicrobial represented by chlorhexidine gluconate. In addition, any OTC active ingredient that is terminally sterilized by ionizing radiation must be submitted to the FDA as an NDA for assessment of safety and efficacy for the desired indication(s). 

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