Faiblesse D'esprit was a Blossom wine, That Darth Alastor kept a readily large supply of on hand in both his ship and other residences. It was originally a Normal Blossom wine, However Darth Alastor, through the use of Sith Alchemy, added ingredients that assisted in the lowering a persons strength of will. A force user would have been effected by this differently. If the user was, Sith, they would have been effected more strongly and lost will power quickly, a Jedi would have had a greater resistance do to their training of the mind, a Grey Jedi would have bedn effected depending on their personality quirks, one who was high on themselves would likely have been effected like a Sith. An active Detoxify Poison or Force Aura may have stop or hinder the effects of Faiblesse D'esprit.