Escitalopram, an antidepressant with an allosteric effect at the serotonin transporter--a review of current understanding of its mechanism of action.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing preclinical pharmacology and mechanistic hypotheses.
PubMed 21901317 · doi:10.1007/s00213-011-2463-5
What was done
This narrative review synthesized literature on the mechanism of action of escitalopram at the serotonin transporter, including in vitro binding assays, neurochemical, neurophysiological, and clinical studies.
What was found
The abstract reports no quantitative values or statistical metrics. Qualitatively, escitalopram binds to the primary orthosteric site on the serotonin transporter to inhibit serotonin reuptake and also binds to an allosteric site that decreases its own dissociation rate. In contrast, R-citalopram acts as an allosteric modulator that negatively interferes with escitalopram binding. Both acute and chronic administration induce cellular, neurochemical, neuroadaptive, and neuroplastic changes.
Why it matters
These allosteric properties provide a biological rationale for clinical observations suggesting escitalopram has higher efficacy and a faster onset of action than racemic citalopram and other antidepressants.
Limits
The paper is an unsystematic narrative review rather than a systematic review. The abstract reports no primary sample sizes or effect sizes, and the link between in vitro allosteric binding kinetics and human therapeutic differences remains a mechanistic hypothesis.
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