ChEBI: A 1-[3-(dimethylamino)propyl]-1-(4-fluorophenyl)-1,3-dihydro-2-benzofuran-5-carbonitrile that has S-configuration at the chiral centre. It is the active enantiomer of citalopram.
Mechanism of action
Escitalopram is the S-enantiomer of citalopram that binds with high affinity and selectivity to the human SERT
equivalent to (±)-citalopram. It has been reported that nearly all the activity resides in the S-enantiomer and
that R-citalopram actually counteracts the action of the S-enantiomer. Studies show that escitalopram
exhibits twice the activity of citalopram and is at least 27 times more potent than the R-enantiomer. The
R-enantiomer inhibits the S-enantiomer at the transporter. Escitalopram's mechanism of action is
common to the SSRIs.
Pharmacokinetics
The pharmacokinetics for escitalopram does not exhibit stereoisomer selectivity and, therefore, is similar to
that for citalopram. Likewise, it exhibits linear pharmacokinetics so that plasma levels increase
proportionately and predictably with increased doses, and its half-life of 27 to 32 hours is consistent with
once-daily dosing. It also has been found that R-citalopram is cleared more slowly than the S-enantiomer.
Therefore, when the drug is used as a racemic mixture (citalopram), the inactive isomer predominates at
steady state. This is an added incentive for use of the enantiomerically pure escitalopram. Escitalopram has
negligible effects on CYP isoforms, suggesting a low potential for drug–drug interactions. Escitalopram is indicated for patients with major depressive disorder, generalized anxiety disorder, panic disorder, and social
anxiety disorder.
