4 Slow-drop infusion versus oral administration of citalopram: Comparison of plasma concentrations of the enantiomers of citalopram and its metabolites

Introduction The pharmacological activity of the chiral antidepressant citalopram (CIT) resides mainly in its enantiomer escitalopram (S-citalopram; S-CIT) rather than in R-citalopram (R-CIT). We reported earlier [1] on plasma concentrations of racemic citalopram measured in patients treated with either slow-drop infusion or oral administration in a double-blind double dummy design. Here, we report on plasma concentrations of the individual enantiomers of citalopram and its metabolites from this study [1].

Methods In the plasma probes collected in this study [1], the steady-state concentrations of citalopram and its metabolites were measured by a stereoselective HPLC procedure. The probes were collected before daily dosing at 7:30 h after a 10-day treatment with 40 mg/day citalopram, administered either p.o. or by slow-drop infusion.

Results In the group with active intravenous infusion (n = 27), the following concentrations were measured: S-CIT: 24 ± 0.2 ng/mL; R-CIT: 45 ± 14.5 ng/mL; S-desmethyl-CIT: 13 ± 4.4 ng/mL; R-desmethyl-CIT: 17 ± 8.2 ng/mL. In the orally treated patients (n = 25), the corresponding figures were: 30 ± 12.7 ng/mL; 51 ± 17.4 ng/mL; 13 ± 4.6 ng/mL; 17 ± 7.9 ng/mL.

Conclusion Due to the high bioavailability of citalopram, the plasma concentrations of the individual enantiomers remained independent from the route of administration. Lower plasma concentrations of S-CIT than R-CIT are a result of their different metabolism.

• References

• 1 Baumann P, Nil R, Bertschy G, Jecker A, Brändli H, Morand J. et al. A double-blind double-dummy study of citalopram comparing infusion versus oral administration. J Affect Disord. 1998; 49: 203-210

Publication History

Article published online:
30 April 2020