Hi Betsy, if your cat likes catnip they will go crazy for it, rolling around and drooling and getting spaced out eyes. If they don't, then they will ignore it - it is apparently genetic if they like it or not. I have had dozens of cats who have ignored it. At present I have two who adore it.
I gave my foster cat a new catnip bag this evening, to see if she knew how to play - she is so drugged up she thinks i am a monster!!
and attacked me when I tried to clean out her litter tray