Don't know about Sartosa, but the Mordheim nets are one use per battle. Well, that is the interpretation that we use in my circle anyway. We only recently noticed that it said 'once per game' and prior to that noone took them at all. Hardly anyone takes them still, but people sometimes taking something is better than never taking them.
We also only just noticed that drugs are once per game also, unlike poisons which are one use only.