The more I think of it the more it makes sense to remove the torture droid altogether.
Vader is a Sith Lord and one of four Force masters left in existence so why would he use drugs when he can play with minds?

Not weak minds.

Vader says her resistance is great and Obi-Wan later explains the Force can only sway the weak minded but it would make more sense to remove the droid and maybe replace it with a close up of Vader’s eyes (if a suitable Vader mask can be had) or maybe his hand in a Force using gesture like the TFA trailer (I haven’t seen the film yet so no spoilers please).

Having Vader trying to probe Leia’s mind unaided would build his character and Leia’s while backing up something Ben would do later do in the film.