Pharmacology · Selective serotonin reuptake inhibitors (SSRIs)
Escitalopram !
An SSRI for depression and generalised anxiety. It is the active S-enantiomer of citalopram and very selective for the serotonin transporter.
Updated 2026-11-01
The figure shows S-citalopram (escitalopram) bound at the central site of a thermostabilised human SERT (ts3).
Mechanism of action
Escitalopram is the S-enantiomer of racemic citalopram, the form that carries the activity. It binds the central site of the serotonin transporter and blocks serotonin reuptake. Crystal structures also show a second, allosteric site in the transporter's outer vestibule.
- Escitalopram binds the central site of the serotonin transporter
- Serotonin reuptake into the neuron is blocked
- Serotonin acts longer at its receptors
- Mood and anxiety improve over weeks
Pharmacokinetics
- Absorption
- By mouth, with or without food
- Metabolism
- Mainly in the liver; CYP3A4 and CYP2C19 carry out the main step (N-demethylation)
- Half-life
- About 27 to 32 hours; longer in older adults
- Onset and duration
- Benefit builds over several weeks
Indications
- Major depressive disorder (adults and adolescents)
- Generalised anxiety disorder
Adverse effects
Common
- Nausea
- Insomnia or somnolence
- Sweating and fatigue
- Sexual dysfunction (ejaculation disorders, low libido)
Contraindications
- MAO inhibitors for psychiatric use, or within 14 days of stopping either drug; not started during linezolid or intravenous methylene blue
- Pimozide
- Hypersensitivity to escitalopram or citalopram
Key interactions
- MAO inhibitors, triptans, tramadol, fentanyl, lithium, St John's wort
- Serotonin syndrome
- NSAIDs, aspirin, warfarin
- Higher bleeding risk
- Citalopram
- Same active molecule: not combined
- Pimozide
- QT prolongation
What is monitored
- Mood and suicidal thoughts, especially early and after dose changes
- Sodium in older adults
- Signs of mania
- Bleeding with antithrombotic drugs
Administration and safety
- Given by mouth as tablets or oral solution, with or without food
- Not given together with citalopram (the same active molecule)
- Stopped gradually to avoid a discontinuation syndrome
Nursing care
- Screen for suicidal thoughts at the start and after each dose change, and teach families what to watch for
- Teach that benefit takes weeks and that stopping suddenly can cause dizziness and irritability
- Watch for confusion, headache or unsteadiness in older adults (low sodium)
- Teach the signs of serotonin syndrome when other serotonergic drugs are added
Pregnancy and breastfeeding
Used in pregnancy after weighing risks and benefits; SSRI exposure late in pregnancy is linked to neonatal adaptation problems and persistent pulmonary hypertension.
Test yourself
Think of the answer, then tap the question to see it.
What is the relationship between escitalopram and citalopram?
Citalopram is a racemic mixture; escitalopram is its S-enantiomer, the form responsible for blocking the serotonin transporter.
Why are escitalopram and citalopram not given together?
They are the same active molecule, so combining them only doubles the exposure and the adverse effects.
What do the human SERT crystal structures show about where escitalopram binds?
It binds the central substrate site, and a second molecule can bind an allosteric site in the extracellular vestibule.
Related drugs
← Back to the class: Selective serotonin reuptake inhibitors (SSRIs)
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - ESCITALOPRAM OXALATE solution (DailyMed (U.S. National Library of Medicine), 2026); Escitalopram: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); 5I73: X-ray structure of the ts3 human serotonin transporter complexed with s-citalopram at the central and allosteric sites (RCSB Protein Data Bank, 2016).
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Representative model, for educational purposes only.