Cats are known to refuse catnip if they have had enough of it. Cats love catnip. Fresh catnip is better than dried catnip.
The good news is that catnip is not harmful to your cat and cats cannot overdose on it. Cats are good at self-regulating and will remove themselves from the experience after a while becoming immune to the effects after 1530 minutes. The greens from catnip are not harmful and outdoor cats often consume it on their prowls plus if it happens to affect the cats nervous system so that it runs around a bit it should be considered a positive in terms of stimulating exercise especially for indoor only cats. Catnip toys are perhaps the most popular way to administer this popular herb to playful felines.