It takes 7 seconds for the extractor to extract the pituitary fluid, and it can be done on practically any NPC.
After the NPC's fluids have been gathered, they'll fall to the ground unconscious.
Events of We Happy Few
Arthur gets the device from completing the side quest, Mother's Little Helper, in which he is instructed to retrieve three pituitary fluids from someone who got in contact with mustard gas, one from a Crier, one from a Bobby and lastly, one from a Joy Doctor.
The player can get the fluids from any random Crier, Bobby, or Doctor. The Doctors at The Hippo Club are a prime target, but any wandering doctor works too.
Once the fluids have been collected, Arthur returns the device.
Sally also gets the pituitary extractor. This happens through one of her story quest, as it is needed for the acquisition of the Blackberry Joy ingredients. She gets to keep it after the quest is done.
Ollie does not get the Pituitary Extractor.
If a crier is in another animation (witnessing a murder) she won't perform her usual extraction animation and will instead stand in place until it's over.