Horses are always biting, tearing and pulling at bandages, often getting themselves in plenty of trouble. Bandages should be removed and reapplied every 8 to 12 hours to assure good circulation. Hydrogen peroxide can be very irritating to tissue, doesn't do much to cleanse a wound and has very little disinfecting action. In most cases, around horses, it's kind of worthless, but people like it because it foams and doesn't sting. Putting medications on a wound that needs to be sutured is mistake No. 5.
Most vets agree, the best thing to do is keep the wound clean by rinsing it with clear, cool water.
If you think there is the smallest possibility a wound will be sutured, don't put anything on it which isn't water soluble. Before suturing, your vet will want to clean the wound thoroughly. Penicillin is readily available to horse owners and often times they get antibiotic happy. The overuse of antibiotics creates a bacteria in the system which is no longer sensitive to further use of the drug. When you actually need it, you want an antibiotic to be effective.