Can i give my hamster cat nip?

True catnip (Nepeta catharria) is actually closely related to plants in the menthe (mint) family.

Some rodents have low tolerance to some species of mint and it may cause them to have digestive problems and diarrhea.

Besides, the "good" effect of Catnip wouldn't happen with a hamster, since its something directly related to the feline instincts.