Chlorhexidine, a synthetic biguanide, is a cornerstone in the field of antiseptics and disinfectants, widely recognized for its potent antimicrobial properties. Understanding its chemical nature and mechanism of action is key to appreciating its significant role in healthcare, dental care, and personal hygiene.

Chemically, Chlorhexidine is a cationic bisbiguanide. Its molecular structure, represented as C22H30Cl2N10, features two biguanide groups linked by a hexane chain, with chlorophenyl groups attached. This cationic nature is fundamental to its antimicrobial activity. At physiological pH, Chlorhexidine salts dissociate, releasing positively charged Chlorhexidine molecules. These positively charged cations are attracted to the negatively charged sites on the surface of bacterial cell walls and membranes.

The primary mechanism of action involves this electrostatic interaction. Upon binding to the bacterial cell surface, Chlorhexidine disrupts the integrity of the cell membrane. This disruption causes essential intracellular components, such as cytoplasmic fluid and genetic material, to leak out of the cell. At lower concentrations, this leads to a bacteriostatic effect, inhibiting bacterial growth. However, at higher concentrations, the damage is more severe, resulting in cell lysis and death – a bactericidal effect.

This broad-spectrum activity extends to a wide range of microorganisms, including Gram-positive and Gram-negative bacteria, as well as yeasts. While effective against many bacteria, it's important to note that Chlorhexidine is not effective against bacterial spores or certain viruses like poliovirus. Its efficacy is also influenced by pH, with optimal activity occurring in a neutral to slightly alkaline environment.

Chlorhexidine is typically available in salt forms, such as Chlorhexidine gluconate (CHG), Chlorhexidine diacetate, and Chlorhexidine dihydrochloride. Chlorhexidine gluconate is particularly popular due to its high water solubility, which facilitates its formulation into various solutions and products. This combination of chemical structure, electrostatic interaction with microbes, and resulting cell disruption makes Chlorhexidine a highly effective and reliable antiseptic agent.