Take amoxicillin, for example. You take it. Your kids take it. Your dog or cat may have been dispensed ''the pink stuff'' or a tablet form of the medication. Because the prime factor that determines what medicine is chosen is whether the infection we're trying to treat is susceptible to that antibiotic.
Different antibiotics kill different bacteria.
As long as the antibiotic doesn't conflict with the internal workings of the patient, it's as good in one species as another. Sometimes the choice of antibiotic is based on the organ that's infected. For example, the medication that the bloodstream will effectively transport to the prostate gland of humans and dogs is likely to be the same. That's because the physical and biochemical barriers that exist between the bloodstream and the prostate gland are similar in both species. The most commonly used medications for the prostate are safe in both species.