poison?

I was wondering about poisons. I want to put poison on my blade. If I hit someone, does that mean the poison is done or can I continue to have that blade be poisoned. It says that if you roll a 1 on an attack it uses the dose but I was wondering about landing an attack

(I know it probably uses it up but I want to be sure)

They only last for one hit unless you have a feat or ability that maks them last longer.