Differential metabolism of citalopram by 21 CYP3A4 variants: An in vitro experiment

Abstract

Background:

Citalopram is widely used for treating major depressive disorder, but exhibits substantial inter-individual variation in clinical response. CYP3A4 is one of the cytochrome P450 enzymes (CYP450) involved in the demethylation metabolism of citalopram. Genetic polymorphisms in CYP3A4 may alter the metabolism of citalopram by affecting the enzymatic activity of CYP3A4.

Aim:

This study aims to evaluate the metabolic differences of citalopram between wild-type and 21 CYP3A4 variants identified in the Chinese Han population.

Methods:

An optimized in vitro incubation system was established, consisting of recombinant human CYP3A4 expressed in Spodoptera frugiperda 21 insect cells and citalopram at various concentrations. The incubation was maintained at 37°C for 30 minutes. Citalopram and demethylcitalopram were quantified using high-performance liquid chromatography with fluorescence detection. Michaelis-Menten curves were plotted, and enzyme kinetic parameters were calculated for each CYP3A4 variant.

Results:

Our results showed that most CYP3A4 variants significantly altered citalopram metabolism. Specifically, 12 variants (*3, *4, *5, *9, *10, *16, *19, *23, *28, *31, *33, and *34) showed a 30.83% to 96.06% decrease in intrinsic clearance (CL_int) compared to wild-type, while five variants (*2, *11, *14, *17, and *18) exhibited a 13.52% to 448.56% increase (p < 0.05). Four mutants (*15, *24, *29, and *32) demonstrated CL_int similar to wild-type.

Conclusion:

This study provides the first systematic data on the impact of CYP3A4 variants on citalopram metabolism, suggesting that CYP3A4 genetic polymorphism plays a significant role in citalopram metabolism, and highlighting its potential value in individualized therapy.