Can I Give Human Antibiotics To A Cat?

There are some that you can, but you should not try without consulting the Vet.
Best thing to do, ask vet.

Yes you can but it will get sick and die

You should not - the chances are that you will kill it or make it very sick due to dosage issues. If you have, for example a pill that contains 100mg of medicine, for a cat you may only need 5mg of that medicine. So you have to cut the pill up into 1/20th sections, and if you make a mistake and give the cat 1/10th of the pill instead, you've just given it a double dose and it could die.

Also, there will probably be issues with the coating on the pill that may also make the cat very sick. Don't do it.

I have a cat that has a abscess on his belly. It is about the size of a quarter and leaking a lot of puss. I just noticed it yesterday and can't afford to take the little guy to the vet, I did however call the vet and was told to wash it out with beta dine, keep him from licking the wound, and make sure he doesn't have fever. I do have some of my antibiotics from an abscessed tooth, that are in capsule form........should I????????? I was also wondering if I should pack the wound like the human Dr. Would if I had a burst abscess? Fluid is leaking everywhere and I think it would heal faster if I were to do a wet to dry dressing. If anyone has advice, I'd sure appreciate it.