Usually at that point poison is not an issue because of potions of cure poison, alraunia or just resistance + regen.
Sometimes however you get poisoned multiple times and it stacks and becomes a threatening situation because of how rapidly it can eat your HP.
I have recently fought two quickling queens from a single post-DH tension room with a sub-level 40 assassin WITH poison resistance from a corpse.
Suddenly my 270ish HP started dropping by 30-35 points EACH turn. I had to drink two blessed potions of cure poison to get rid of it after teleporting to a safer part of the level.
Just 10 turns later both quickling queens found me and poisoned me again. Blessed spenseweed could not counter the amount of poison damage per turn that I was getting.
I had to retreat upstairs and return with unerring ammo and wand of fireballs because of this.
"Hell is empty and all the devils are here."