Determination of plasma levels of citalopram and its demethylated and deaminated metabolites by gas chromatography and gas chromatography-mass spectrometry.
Sensitive and specific methods based on gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) for the determination of levels of citalopram, desmethylcitalopram and didesmethylcitalopram in the plasma of patients treated with citalopram are presented, as well as a GC-MS procedure for the assay of the citalopram propionic acid derivative. After addition of a separate internal standard for each drug, liquid-solvent extraction is used to separate the basic compounds from the acid compounds. The demethylated amines are derivatized with trifluoroacetic anhydride, and the acid metabolite with methyl iodide. GC-MS is performed in the electron impact mode, as mass spectrometry by the (positive-ion) chemical ionization mode (methane and ammonia) appeared to be unsuitable. The limits of quantification were 1 ng/ml for citalopram and desmethylcitalopram and 2 ng/ml for the other metabolites. The correlation coefficients for the calibration curves (range 10-500 ng/ml) were > or = 0.999 for all compounds, whether determined by GC or GC-MS.
Unite de Biochimie et Psychopharmacologie Clinique, Département Universitaire de Psychiatrie Adulte, Prilly-Lausanne, Switzerland.
P
P
Reymond
M
M
Amey
A
A
Souche
S
S
Lambert
H
H
Konrat
C B
CB
Eap
P
P
Baumann
D000929:Antidepressive Agents, Tricyclic / Q000032:analysis; D002849:Chromatography, Gas; D015283:Citalopram / Q000097:blood*; D003640:Dealkylation; D003641:Deamination; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007202:Indicators and Reagents; D012015:Reference Standards
D000929:Antidepressive Agents, Tricyclic; D007202:Indicators and Reagents; D015283:Citalopram