How much Penicillin Do I Give A Very Sick Cat?

A cat showed up at my house a couple of weeks ago that I had never seen before. A very pretty boy and I just thought it was there because my female cat went into heat. After my female cat got spayed the cat still lingered around and went back and forth to all the neighbors houses. Yesterday, it came on my porch and ran in the house. I noticed he is sneezing really badly and is very congested. All I have on hand is injectable penicillin and cant afford to take him to the vet. How much, where, and how often would I give this to kitty?

It's really not a good idea to give a cat any kind of medication unless you've been to see a vet. Not all antibiotics are suitable for treating colds and respiratory problems and cats can have a allergic reactions to penicillin, just as people can.

Is there a humane society in your area? How about a No-Kill shelter you could take the cat to? If he's tame enough for you to consider giving an injection to he could well be someone's missing pet.

He's likely to get injured running around outside. I think the best thing to do is try to get him to a shelter to be scanned for a chip and given the medical attention he needs.