Chlorhexidine digluconate is an antiseptic agent of the biguanine group with a broad-spectrum bactericidal activity against gram-positive and gram-negative bacteria as well as a fungicidal activity against yeasts.
The mode of action of chlorhexidine (i.e. whether it is bactericidal or bacteriostatic) depends on the concentration used. Chlorhexidine alters the permeability of the bacterial-cell wall. At low concentrations, low molecular-weight substances leak out without the cell being irreversibly damaged. At higher concentrations, chlorhexidine enters the cell, causes precipitation of the cytoplasm, prevents repair to the bacterial-cell membrane and causes the destruction of the bacterial cell.
Typical MIC values found in clinical Malassezia pachydermatis isolates are 2-4 µg/ml (2008).
To date (2009) no resistance to chlorhexidine has been shown for Malassezia pachydermatis.
Resistance to chlorhexidine is uncommon in Gram (+) bacteria but some resistant Gram (-) isolates have been described in human hospital environments (Proteus spp., Pseudomonas spp.).
When used in accordance with the recommended dose regimen the development of resistance to chlorhexidine is not expected.
After topical administration of the product to dogs, there was little or no systemic absorption of chlorhexidine digluconate. Absorption of chlorhexidine after oral administration is also very low. The efficacy of the product is due to the high concentrations of chlorhexidine digluconate achieved on the body surface for the 10-minute period of shampooing.