Quantification of imipramine and its major metabolites in whole blood, brain, and other tissues of the rat by liquid chromatography

Rapid microsample analysis of imipramine and desipramine by reversed-phase high-performance liquid chromatography with ultraviolet detection

A rapid and highly sensitive HPLC assay method was developed to measure small amounts of imipramine and its major metabolite, desipramine. The assay involved simple extraction procedures using clomipramine as the internal standard. The mobile phase consisted of acetonitrile (60%) and 0.01 M triethylamine in distilled water (40%) with the pH adjusted to 3.0. Separations were achieved on a C18 column and the effluent measured for UV absorption at 260 nm. The chromatographic separation was excellent, with no interference from endogenous serum constituents. This assay was suitable for measuring drug concentrations in the range of 10-1000 ng/ml using a 0.1-ml serum sample. The method was applied to a drug disposition study in transgenic mice with increased plasma alpha 1-acid glycoprotein.

The effect of ranitidine and cimetidine on imipramine disposition

The pharmacokinetic characteristics of imipramine were studied after a single, oral, 100 mg dose was taken by 12 healthy male subjects following 3 days of pretreatment with placebo, cimetidine (300 mg every 6 h), and ranitidine (150 mg every 12 h) in a randomized, double blind, crossover trial. After each imipramine dose plasma samples were collected for 72 h and assayed for imipramine, desipramine, 2-hydroxyimipramine and 2-hydroxydesipramine by HPLC. Cimetidine preadministration statistically prolonged imipramine t 1/2 compared to ranitidine (22.7 vs. 13.0 h) or placebo (10.8 h). Mean imipramine area under the curve (AUC) following cimetidine pretreatment was more than double that following placebo (2.633 vs. 0.966 micrograms X h X ml-1) or ranitidine (1.14 micrograms X h X ml-1) pretreatment. Imipramine apparent oral clearance was reduced in all 12 subjects after cimetidine. Compared to ranitidine or placebo, cimetidine pretreatment was associated with an increased imipramine/desipramine AUC ratio, suggesting cimetidine-induced impairment of demethylation of imipramine. Ranitidine was not observed to alter imipramine pharmacokinetics.

Cerebral and blood pharmacokinetics of imipramine and its active metabolites in the pregnant rat

A single IP dose of imipramine (IMI) was administered to pregnant rats. Whole blood, plasma, and brain concentrations of IMI, desipramine (DMI), and their 2-hydroxylated metabolites were separated by high-pressure liquid chromatography and quantified by fluorescence detection. IMI and DMI rapidly appeared in brain tissue in concentrations greatly exceeding those in whole blood and plasma. The much higher concentration and longer persistence of DMI in brain compared to IMI suggests that the predominant central effects from administered IMI result from biotransformation to DMI. The metabolite: "parent" area under the curve ratios for the hydroxylated metabolites indicate that their contribution to the pharmacologic effects of IMI and DMI are probably negligible.