Desmethylimipramine overdose: nonlinear kinetics in a slow hydroxylator.

A case of desmethylimipramine (DMI) overdose is described. The analysis of DMI and its main metabolite, 2-hydroxydesmethylimipramine (2-OH-DMI), in plasma was performed by high performance liquid chromatography with fluorescence detection. Characterization of the elimination kinetics of DMI by using the SAAM 25 computer program indicated Michaelis-Menten kinetics. The patient was phenotyped with respect to debrisoquine hydroxylation and classified as a slow hydroxylator. Both nonlinear kinetics and slow hydroxylation might have contributed to the marked difference between the concentration of DMI and 2-OH-DMI in plasma in this patient.