 However, the transesterfication process of methylphenidate to ethylphenidate, as tested in mice liver, was dominant in the inactive (−)-enantiomer but showed a prolonged and increased maximal plasma concentration of the active (+)-enantiomer of methylphenidate.Additionally, only a few percent of the consumed methylphenidate is converted to ethylphenidate.This carboxylesterase-dependent transesterification process is also known to occur when cocaine and alcohol are consumed together, forming cocaethylene.