Specific Effects of Escitalopram on Neuroendocrine Response
Status:
Completed
Trial end date:
2007-12-01
Target enrollment:
Participant gender:
Summary
Citalopram, a selective serotonin reuptake inhibitor (SSRI), is used as a neuroendocrine
probe in human subjects to assess serotonin (5-hydroxytryptamine; 5-HT) function as reflected
in prolactin and plasma cortisol release. Citalopram is a racemic mixture of equal parts of
the S(+) and R(-) enantiomers. The S(+) form ("escitalopram") has been identified as being
the active isomer and inhibitor of serotonin reuptake and consequently antidepressant
activity is associated almost exclusively with the S-enantiomer. Escitalopram has been shown
to be approximately twice as potent as citalopram at the primary, high-affinity binding site
on the human serotonin transporter. Interestingly, investigations have suggested an
antagonistic interaction of the R- and S-enantiomer at an allosteric binding site on the
serotonin transporter. This antagonism has been shown in animal studies where the addition of
R-citalopram to escitalopram treatments significantly counteracts the antidepressant and
anti-anxiolytic effects of escitalopram. From these clinical and experimental data, the
researchers can anticipate that escitalopram would increase cortisol and prolactin in the
neuroendocrine challenge paradigm more effectively than citalopram.