pethidine1-methyl-4-phenyl-4-piperidinecarboxylic acid ethyl ester1-methyl-4-phenylisonipecotic acid ethyl ester1-methyl-4-phenylpiperidine-4-carboxylic acid ethyl esterIDS-NP-001N-methyl-4-phenyl-4-carbethoxypiperidineethyl 1-methyl-4-phenylisonipecotateisonipecainemeperidinameperidinemethyl phenylpiperidine carbonic acid ethyl esterpethidinpethidineterpetydynaphetidine