Karneval will be getting another drama CD release in March 2010, main cast will stay the same but a few new characters have been added.
Karoku - Sōichirō Hoshi (Gino from Code Geass R2, Sanada Yukimura from Sengoku Basara)
Doctor - Ken'ichi Ogata
Erishuka - Satomi Satō (Ritsu from K-On!)
Source
The first drama cd was release in Dec 09.