Chlorhexidine's antimicrobial effects are associated with the attractions between chlorhexidine (cation) and negatively charged bacterial cells. After chlorhexidine is absorpted onto the organism's cell wall, it disrupts the integrity of the cell membrane and causes the leakage of intracellular components of the organisms.
Chlorhexidine, a topical antimicrobial agent, is bactericidal. Because of its positive charge, the chlorhexidine molecule reacts with the microbial cell surface to destroy the integrity of the cell membrane. This novel mechanism of action makes it highly unlikely for the development of bacterial resistance.
LD50= 2g/kg (human, oral); LD50= 3 g/kg (rat, oral); LD50= 2.5 g/kg (mice, oral); LD50= 21 mg/kg (male rat, IV); LD50= 23 mg/kg (female rat, IV); LD50= 25 mg/kg (male mice, IV); LD50= 24 mg/kg (female mice, IV); LD50= 1g/kg (rat, subcutaneous); LD50= 637 mg/kg (male mice, subcutaneous); LD50= 632 mg/kg (female mice, subcutaneous)
McBain AJ, Bartolo RG, Catrenich CE, Charbonneau D, Ledder RG, Gilbert P: Effects of a chlorhexidine gluconate-containing mouthwash on the vitality and antimicrobial susceptibility of in vitro oral bacterial ecosystems. Appl Environ Microbiol. 2003 Aug;69(8):4770-6. Pubmed