RESEARCH MONOGRAPH · KDC-MN-205
Escitalopram
Escitalopram (Lexapro) is the active half of citalopram pulled out and sold on its own. Lundbeck and Forest Pharmaceuticals brought it to market in 2002 after demonstrating that the inert mirror-image partner in racemic citalopram does nothing useful and may slightly hinder the active component. The mechanism is the same single-target serotonin reuptake block, just cleaner. It is the most serotonin-selective SSRI in clinical use, with very little crossover to the norepinephrine or dopamine pumps. Head-to-head trials suggest a small but real advantage in efficacy and tolerability over citalopram, which is why most prescribers now reach for it first. The dose ceiling is much lower (20 mg) because each milligram contains only the active half. Not stocked by Kodiac. This monograph is provided for research and educational reference.
Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.
S-enantiomer SSRI
The (S)-enantiomer of citalopram; the active component of the racemate marketed as a separate antidepressant with improved tolerability.
Abstract
Escitalopram (S-(+)-1-[3-(dimethylamino)propyl]-1-(4-fluorophenyl)-1,3-dihydro-2-benzofuran-5-carbonitrile; CAS 128196-01-0; molecular formula C20H21FN2O; molecular weight 324.39) is the (S)-enantiomer of citalopram, marketed as Lexapro by H. Lundbeck and Forest Pharmaceuticals after FDA approval in 2002. SERT affinity is approximately 1 nM; selectivity for SERT over NET and DAT is the highest of any clinical SSRI. The active enantiomer is responsible for essentially all SERT inhibitory activity in racemic citalopram; the (R)-enantiomer attenuates (S) binding through an allosteric SERT interaction, so removing it produces a small but measurable increase in serotonergic efficacy per milligram. Plasma half-life is approximately 27 to 32 hours, slightly shorter than racemic citalopram. Hepatic metabolism via CYP2C19 with secondary CYP3A4 and CYP2D6 contribution. The compound exhibits the QTc prolongation profile of racemic citalopram but with a cleaner adverse event signature owing to the absence of the (R)-enantiomer. Approved for major depressive disorder and generalized anxiety disorder. Used as a high-purity SERT-selective reference compound in mechanism studies.
Mechanism of action
Same SERT inhibition as racemic citalopram, attributable entirely to the (S)-enantiomer. Highest SERT selectivity among clinical SSRIs.
Reported research dose ranges
Reported research dose ranges in the literature.
References
- Sanchez C, et al. 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 2003.
- Burke WJ. Escitalopram. Expert Opin Investig Drugs 2002.
- Owens MJ, et al. Second-generation SSRIs: human monoamine transporter binding profile of escitalopram and R-fluoxetine. Biol Psychiatry 2001.
Read the full monograph
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The full reference document is provided strictly for research use only. It reports research dose ranges from the published literature, not instructions for use in humans or animals.
FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.