What are you using the penicillin for? Procaine Penicillin G which is found in the refrigerated medicines in many feed stores, and it is only given by injections into the breast muscle. It cannot be given in the water or orally as some medicines may be. It can be used to treat wounds. Amoxicillin, a synthetic penicillin can be given orally with a needle-less syringe, but it settles out in water.