Shin'eiyaku

are pills designed by Kisuke Urahara to help Shinigami who have lost their Bankai to Quincy Medallions. By temporarily causing the user to Hollowfy, it effectively makes the Bankai "poison" for a Quincy due to their inability to take in Hollow Reiatsu without their souls being destroyed in the process. The pills are taken through any means of physical contact. The effects were first seen when Toshiro Hitsugaya's stolen Bankai, Daiguren Hyōrinmaru, broke and suddenly injured Cang Du.