Retrospective Pilot Study for Analysis of Antidepressant Serum Concentrations of Citalopram and Venlafaxine during Inflammation

Abstract

Introduction: Inflammation-mediated changes in drug metabolism may increase drug levels in blood and lead to intoxications. The objective of this study was to find out whether elevated serum levels of C-reactive protein (CRP) are associated with increased serum concentrations of the antidepressants citalopram and venlafaxine.

Methods: Therapeutic drug monitoring request forms of psychiatric patients were screened retrospectively. The serum concentrations in relation to the daily doses [(C/D) (ng/ml/mg)] and the metabolic ratios (metabolite/drug) were compared intraindividually under normal (<5 mg/l) and pathological (>5 mg/l) condition by the Wilcoxon signed-rank test.

Results: Elevated levels of CRP were not associated with a significant (P>0.05) increase in C/D for citalopram (2.4 ng/ml/mg vs. 2.85 ng/ml/mg, N=15) or in C/D for the active moiety of venlafaxine (1.76 ng/ml/mg vs. 1.68 ng/ml/mg, N=39), compared with normal CRP serum levels. No significant difference in the metabolic ratio was observed in both groups.

Discussion: There was no major effect of inflammation on the metabolism of citalopram and venlafaxine. Because of the broad therapeutic indices of these 2 drugs, the drugs seem to be a good choice for the treatment of depression, even if an infection occurs.

Key words

C-reactive protein - venlafaxine - citalopram - antidepressants - therapeutic drug monitoring - pharmacokinetics - drug metabolism - psychiatry

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