Chlorhexidine is still widely used as an antiseptic for hand washing, as a surgical scrub and as a navel dip for foals and
wound irrigation. Discovered in the late 1940s, chlorhexidine showed rapid bactericidal activity against various nonspore-producing
bacteria by damaging the outer cell layers and causing leakage of the cytoplasmic membrane. Antibacterial activity against
Staphylococcus aureus, Pseudomonas aeruginosa and other bacteria has been reported, but methicillin resistance has also been noted, keeping chlorhexidine from being a
first choice for wound treatment.
"Despite reports of decreased bacterial counts, increased healing rates and a lack of toxicity, it was concluded that, at
present, there is insufficient data to assess safety and efficacy," says Cooper, who thinks further clinical trials are required
before this agent can be either recommended or condemned.
Honey is another old remedy that has been making a strong comeback, and various researchers have identified nearly 70 bacterial
species susceptible to its actions, along with evidence that its use will promote healing in topical wounds. The antimicrobial
action of honey arises from the osmolality, acidity and hydrogen peroxide created on the wound surface when it's used and
from the presence of yet-unidentified honey phytochemicals.
Cooper cautions that "geographic location, floral origin and post-harvesting treatment conditions of individual products may
also be important to its action." Published reports stress that the type of honey used is extremely important, and honey advocates
and enthusiasts aggressively debate the merits of manuka honey vs. jelly bush, among others.
Particularly impressive and encouraging is honey's bactericidal action against methicillin-resistant S. aureus (MRSA) and vancomycin-resistant enterococci (VRE), which are proving to be difficult microbes for more traditional antibiotics
to handle. Honey operates by targeting multiple, nonspecific cellular sites, thus making it more difficult for microbes to
overcome this agent. Multiple animal studies have identified honey's ability to promote wound healing and have documented
its use in treating many types of distal limb wounds.
R. Reid Hanson, DVM, Dipl. ACVS, Dipl. ACVECC, of the Department of Clinical Sciences, College of Veterinary Medicine at Auburn
University, has published extensively on the management and healing of equine wounds and burns, and he spoke about equine
distal limb wounds at the 80th Western Veterinary Conference. "Honey has many useful properties, including broad-spectrum
antimicrobial activity, anti-inflammatory action and stimulation of new tissue growth," reports Hanson. "The stimulatory effect
of honey on wound healing may, in part, be related to up-regulation of anti-inflammatory cytokines—tissue necrosis factor,
interleukin 1 beta, interleukin 6—within monocytes."
While most practitioners simply add pure honey to a nonstick wound dressing and apply this under a wrap, the development of
actual wound care products containing honey is well underway. The production of standardized, purified honey and sterile dressings
impregnated with honey will improve reliability, make it easier for veterinarians to use this agent and promote more controlled
clinical trials that should generate more useful data on this ancient remedy.
Hydrogen peroxide is an antiseptic and disinfectant product that has also been around for a long time. It has broad-spectrum
activity against bacteria, principally gram-positive species. It exerts its effect through oxidizing properties that produce
free radicals to react with lipids, proteins and nucleic acids that disrupt cellular activity and kill microbes. Negative
reports of air emboli and tissue irritation with hydrogen peroxide use have caused some to back off on its utilization, and
there's insufficient research to make definitive statements about the place of hydrogen peroxide in wound management.