Escitalopram （Lexapro，Cipralex）is a selective inihibitor of serotonin(5-HT) reuptake (SSRI) with a Ki value of 6.6nM for [3H]-5-HT uptake [1].

Escitalopram is the S-(+)-enantiomer of citalopram and has the inhibition of [3H]-5-HT uptake and [125I]-RTI-55 binding in COS-1 cells expressing the human serotonin transporter (5-HTT) with Ki values of 6.6±1.4nM and 3.9±2.2nM, respectively. In addition, Escitalopram has been reported to inhibit the accumulation of 3H-labelled monoamines into rat brain synaptosomes in vitro with IC50 values of 2.1±0.75nM, 2500±202nM and 40000±15500nM for [3H]-5-HT, [3H]-I-NA and [3H]-DA, respectively. Apart from these, Escitalopram has shown the in vitro affinity for rat histamine H1 receptors and the rat sigma σ1 site with Ki values of 1500±780nM and 100±71nM, respectively [1].

References:
[1] Sánchez C1, Bergqvist PB, Brennum LT, Gupta S, Hogg S, Larsen A, Wiborg O. Escitalopram, the S-(+)-enantiomer of citalopram, is a selective serotonin reuptake inhibitor with potent effects in animal models predictive of antidepressant and anxiolytic activities. Psychopharmacology (Berl). 2003 Jun;167(4):353-62. Epub 2003 Apr 26.