The impact of CYP2C19 polymorphisms on citalopram metabolism in patients with major depressive disorder

What is known and objective: Genetic variations in drug-metabolizing enzyme genes change drug pharmacokinetics and response. CYP2C19 is a clinically important enzyme that metabolizes citalopram (CIT). The objective of this study was to determine CYP2C19 genetic polymorphisms and to evaluate the impact of these polymorphisms on the metabolism of citalopram in a sample of the Turkish population. We also assessed *17 polymorphism in healthy subjects in this population.

Methods: The CYP2C19 genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism method (209 healthy individuals and 50 patients for CIT metabolism), and the plasma concentrations of CIT and demethylcitalopram (DCIT) were quantified by high-performance liquid chromatography.

Results and discussion: The CYP2C19*1 and *17 allele frequencies for the patient group and the healthy group were 71·0%, 18·0% and 81·1%, 18·9%, respectively. There was no significant difference between the two groups (P > 0·05). The mean plasma concentrations and the mean dose-corrected (C/D) plasma levels of DCIT were significantly higher in patients with the CYP2C19*1/*1 genotype compared to patients with CYP2C19*1/*2 and CYP2C19*2/*2 genotypes (P < 0·05). Furthermore, the mean metabolic ratio (MR, CIT/DCIT) was also significantly higher in the CYP2C19*1/*2 + CYP2C19*2/*2 genotypes (P < 0·05). On the other hand, plasma CIT, DCIT concentrations and M/R value in the CYP2C19*1/*1 genotypes were no different to those of the CYP2C19*1/*17 genotypes (P > 0·05).

What is new and conclusion: Our data suggest that CYP2C19*17 polymorphism does not have a significant effect on CIT metabolism. In contrast CYP2C19*2 polymorphism has a prominent role and is likely to contribute to interindividual variability in CIT metabolism in vivo at therapeutic doses.