BCHE and cocaine dependence: Butyrylcholinesterase (BChE; EC 3.1.1.8) and its genetically engineered variants are being developed as therapeutic enzyme “bioscavengers” of organophosphorus acid anhydrides (OPAA) to prevent or treat OPAA poisoning (Millard et al., 1995a; Doctor and Saxena, 2005; Saxena et al., 2006) and also have been investigated to reverse cocaine addiction (Xie et al., 1999; Zheng and Zhan, 2008; Masson and Rochu, 2009).