IN VITRO TRANSESTERIFICATION OF COCAETHYLENE (ETHYLCOCAINE) IN THE PRESENCE OF ETHANOL Esterase-Mediated Ethyl Ester

This study reports that cocaethylene undergoes an esterase-me-diated ethyl ester exchange with ethanol, resulting in an increase in the apparent in vitro t1⁄2, compared with control conditions. Ho-mogenized liver from male Sprague Dawley rats in pH 7.4 phos-phate buffer was centrifuged at 9000g, and the resulting superna-tant (S9) fraction was collected. Tubes containing the rat S9 fraction and 50 mM cocaethylene plus aqueous buffer (control), 50 mM ethanol, or 51.3 mM 2H6-ethanol were incubated at 37°C for 4 hr. Samples were collected from the incubation tubes at various times, extracted with a solid-phase extraction system, and as-sayed for cocaethylene and 2H5-cocaethylene by GC/MS. Concen-tration-time profiles were constructed and kinetic parameters were determined. The experiment was repeated in the presence of specific and nonspecific esterase inhibitors. Enzyme kinetic pa-rameters were also determined. Cocaethylene underwent ethy