Catnip's nepetalactone triggers sniffing, licking, and rolling through olfactory pathways, with sensitivity inherited, so a substantial fraction of cats never respond.
Silvervine contains several active compounds and excites many catnip non-responders, so alternating the two keeps novelty alive.
Responses last a few minutes followed by a refractory period, and frequent offering dulls the effect, so once or twice weekly is plenty; weak kitten responses are normal.
Nibbling small amounts of dried material is generally safe but excess can cause vomiting or diarrhea; excited play can turn rough, so separate cats during sessions.
