Synthesis of deuterium-labeled imipramine using acid-catalyzed exchange reaction

Stable isotope coadministration methodology for the estimation of the fraction of imipramine metabolized to desipramine

The application of a stable isotope coadministration technique for estimating the fraction (fm) of imipramine (IP) that is converted to desipramine (DMI) is described. Four healthy male subjects received 25 mg of IP-d4 hydrochloride orally with 25 mg of DMI hydrochloride. The plasma concentrations of IP-d4, DMI-d4, and DMI were determined by capillary gas chromatography-mass spectrometry-selected ion monitoring using d8 analogues as internal standards. The fm values, calculated from the ratio of the area under the plasma concentration-time curve of DMI-d4 to that of DMI, varied from 0.54 to 0.85.

Simultaneous determination of imipramine, desipramine and their deuterium-labelled analogues in biological fluids by capillary gas chromatography-mass spectrometry

A specific, sensitive and accurate method for the determination of imipramine, desipramine and their d4 analogues in biological fluids using d8 analogues as internal standards using capillary gas chromatography-chemical ionization mass spectrometry was developed. Drug concentrations were measured by selected-ion monitoring of the quasi-molecular ions of imipramine and the trifluoro-acetyl derivative of desipramine. The coefficient of variation and relative error at a concentration of about 2 ng/ml in plasma were found less than 10% and 7%, respectively, for both drugs. No isotope effect was observed following the oral administration of an equimolar mixture of imipramine and [2H4]imipramine to a rat.