Feline amoxicillin is the leading antibiotic used to treat bacterial infections in cats. It is a highly-effective medicine that can quickly and dramatically reduce the levels of harmful bacteria in your pet's system. Unfortunately, it does have negative effects and may not be the best choice for certain animals.
Diarrhea
The single most common side effect of amoxicillin in cats is diarrhea. The antibiotic eliminates the healthy bacteria in your pet's digestive tract along with any harmful bacteria there or elsewhere in his body. The result is that your cat's system cannot properly digest and pass the food that he ingests, and he develops bacteria. This does not occur in every case. If your cat does develop bacteria alongside his antibiotic treatment, speak with a veterinarian.
Reactions with other Drugs
Amoxicillin may react negatively with other antibiotics in your pet's system. Be careful to tell your vet of all other medical conditions and medicines affecting your cat at the time of your appointment and before you begin to give him amoxicillin. These negative effects are entirely preventable, but they do require that your foresight.
Generally, amoxicillin is safe for use in all cats. There is a chance of an allergic reaction to the drug, however, and you should be aware of any and all unusual behaviors or physical signs that your cat develops immediately after taking amoxicillin. If you notice any, consult with a veterinarian right away.