@swrazor That's an awesome question!
I guess most of my books have at least one sleepy sedation in them, but I had to scroll through them to figure out which of them had the most and the slowest sedations.
These are the selections I came up with:
Drugged Damsels
It's a collection of short stories all involving ladies getting sleepy.
Caged
A girl gets trapped in a futuristic dome where they continuously sedate her as she tries to escape. (It has a science fiction setting.)
The Loving Lesbians of Sweet Dreams Spa
It's about a spa complex that uses specific gasses that help the clients relax even more, the main character gets addicted so she's there very very often. (there's some mild hypnosis as well but not much and always combined with the sleepy drugs.)
Also and this may be a bit of a wildcard, but there is a lot of F/f sedation in the story
Brainwashed By A Billionaire, yet as the title and the cover imply there is also some brainwashing / hypnosis and there is some forced ageplay / forced regression as well, it's all very gradual and sleepy and they're balancing on the edge of consciousness for quite some time. Yet if ageplay / forced regression is not your thing better skip this one.
I guess on Amazon most characters learn to like the sleepiness, because Amazon can be quite harsh with banning authors and banning books if there are too much 'forced' vibes. Yet I have another book called:
Drugged Revenge it isn't available on Amazon for the reasons described above, but it's available on smashwords. It's a girl getting revenge on the school bully by keeping her drugged up, it has a high concentration of F/f sedation scenes as well.
I hope that was helpfull! If you end up buying a novel please let me know how you liked it!