Kankuro fell down after a few minutes after being stabbed by Hiruko's tail, Sakura fell down after a few seconds after being hit by Iron Sand: World Order, so it depends on how severe the wound is, but it was definitely a bigger wound than Kankuro's so she should've fallen down in a minute.
That would mean that she wouldn't need the antidote at all...
Hardly a plot hole. I believe Chiyo said to Naruto n'all when she was healing Gaara that she was gone for anyway cause of the poisen.
It's an unexplained plot hole, I care.
Yes, but you get paralyzed within a minute. That's what I mean.