User blog comment:Xilinoc/Ch. 552 - The Fundamental Virulence/@comment-5695542-20131008224031/@comment-11051098-20131009152134

It's been stated that the owner of the medallion that stole the Bankai, can use it by will, even after the death of the Shinigami who had the Bankai.

I suspect that once Hitsugaya consumed the pill and Daiguren Hyôrinmaru was slightly affected by Hollow-powers, Cang Du's body couldn't stand wielding it. I think that's what happened, and how the Bankai "became poison to his body".