My first line of defence before a trip to the vet is flush the wound with saline then fill the area with mastitis infusion, then to the vet if it is bad enough. My vet writes a script for oral penicillin powder about once a year to take care of stuff that doesnt warrant a visit.
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You would not be able to give the cat an appropriate dose of the equine formulation. Sulfonamides in small animals are more commonly given as a sulfa-trimethoprim combination to make them kill bacteria (bactericidal) versus stopping the growth (bacteriostatic). Cats generally do not appreciate the taste, so I did not commonly use them in cats. Amoxicillin and Clavamox are more common. If it is a superficial wound I would rinse well with sterile saline or clean gently with hydrogen peroxide, and apply just neosporin ointment or Nolvasan ointment.
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