My cat have black stuff coming out of his eye. ?

I have just given my cat capsar for fleas and since than she has be waking up with balck * coming out of her right eye. Also she cleans out the house when she uses the litterbox (it stinks so bad!)
Is something wrong w/ my cat or is this a side effect from the prescription? Thanx.
Answers:    black stuff comes out of my cat's eyes sometimes too. just tiny bits. it always has. but that's newly the way that he naturally cleans out the muck from in his eyes. Are you certain that's a side effect of the medication? Is it just small amounts?
Well, I'm not sure it is normal or not because I am not a cat owner (Bird owner), but I do know that you should give somebody a lift your cat for a checkup. Just in case. It may cost a little but anything is worth it for our adorable animal friends right? I am thinking that the drug had caused this problem.
My first time have a CAT what do I do?   Need comfort beside flea infested kitten?   How copious legs do cats own?   Cats, fireworks, third eyelids, aggressive demeanour?