plasma hydrolyses, no dependence upon the pK(a) of the carboxylate leaving group was observed, nor was there any dependence upon the amide N-substituent. The rate of decomposition was inhibited by the carboxylesterase inhibitor eserine but not by the cytochrome P450 inhibitor SKF-525A, indicating the involvement of esterases in the hydrolysis reaction. These results indicate that amidomethyl esters