Stereoselective HPLC-Assay for Citalopram and Its Metabolites

Abstract

The racemic selective serotonin reuptake inhibitor citalopram (CIT) is increasingly used for depressive disorders. As both enantiomers of CIT differ in pharmacologic activity and demethylated metabolites might contribute to the antidepressent action of CIT, a stereoselective assay for all active compounds is needed, but will require that pharmacokinetic/pharmacodynamic relationships be investigated. A stereoselective high-performance liquid chromatography (HPLC)-assay (Chirobiotic V column) with UV-detection (lambda = 240 nm) for R- and S-CIT as well as both enantiomers of desmethyl(DM)-CIT and didesmethyl(DDM)-CIT was developed. The calibration range was linear from 5 to 200 ng/mL and the lower limit of detection averaged 2 ng/mL. Based on three quality controls (10, 75, and 150 ng/mL) the intraday and interday coefficients of variation ranged from 1.3% to 9.0% for CIT and from 2.2% to 10.3% for DM-CIT and DDM-CIT. The assay was used to analyze the trough steady state plasma levels of all 6 agents in 16 elderly patients treated daily with 20 to 40 mg CIT. For the dose of 20 mg (n = 14) mean values +/- SD of R- (and S-CIT) averaged 36.2+/-15.0 (27.4+/-13.1) ng/mL, respectively (mean R/S-ratio: 1.4+/-0.4), for R- (and S-DM-CIT) 7.2+/-3.1 (7.7+/-3.8) ng/mL, respectively (R/S-ratio: 1.0+/-0.3) whereas DDM-CIT was only detectable as R-enantiomer in 8 cases (13.2+/-12.1 ng/mL; range: 2.2-36.2 ng/mL). Significant (p < 0.01) linear correlations could be found between both enantiomers of CIT and DM-CIT as well as between parent drug and primary metabolite for the R-enantiomers. Apparently R/S- and metabolic ratios increased with dose; this might indicate that stereoselective disposition of CIT and DM-CIT is concentration-dependent. The present assay allows a rapid, sensitive, and reliable stereoselective determination of CIT and its (active) metabolites which can be applied for assessing pharmacokinetic parameters and evaluating putative relationships to clinical (side) effects.

In vivo steady‐state pharmacokinetic outcome following clinical and toxic doses of racemic citalopram to rats

“…This result opposites the human studies, where the S/R DCIT ratios were somewhat higher than the S/R CIT ratios (Foglia et al, 1997;Rochat et al, 1995a, b;Sidhu et al, 1997;Zheng et al, 2000). Surprisingly, the serum S/R DCIT ratios in the CIT-20 rats were much lower than the serum S/R CIT ratios (0.37 versus 0.83).…”

“…The S/R ratios of CIT from the groups treated with clinical doses of CIT (i.e. the CIT-10 and CIT-20 groups) can also be compared with S/R CIT ratios from human studies (Foglia et al, 1997;Rochat et al, 1995a, b;Sidhu et al, 1997;Zheng et al, 2000). Our data were not in complete agreement with these studies, where the mean S/R CIT ratios were found in the 0.5 ± 0.7 interval, indicating that the R-enantiomer of CIT was present in higher proportion compared with our data.…”

Development and Validation of a Chiral HPLC Method for Quantitative Analysis of Enantiomeric Escitalopram

“…17 However, in order to quantitative analyses of the enantiomeric composition of citalopram, various analytical methods have been developed in recent years. [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] Most of them are involved in the employment of HPLC or supercritical fluid chromatography (SFC), equipped with chiral stationary phases. This study, presents a new, rapid, accurate, precise and the suitable analytical method for seperation of citalopram and the determination of enantiomeric purity of escitalopram with the chiral column composed of silica-based phenylcarbamated β-cyclodextrin (chiral CD-PH).…”

Stereoselective determination of demethyl‐ and didemethyl‐citalopram in rat plasma and brain tissue by liquid chromatography with fluorescence detection using precolumn derivatization

“…With regard to the monitoring of (−)-(R) and (+)-(S) enantiomers of CIT and of their metabolites, different HPLC (Kosel et al, 1998;Rochat et al, 1995;Zheng et al, 2000) and CE stereoselective methods have been developed. To date, all these methods have dealt with the use of chiral chromatographic columns and none of them use an indirect method based on the derivatization with a chiral reagent.…”

“…It is not the aim of this work to determine the presence of citalopram enantiomers, as there are already published methods available for this purpose which have proven to be effective Kosel et al, 1998;Mandrioli et al, 2003;Zheng et al, 2000).…”