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# Citalopram

An SSRI for depression, the racemic parent of escitalopram. It prolongs the QT interval in a dose-dependent way, so heart risk factors matter.

Updated 2026-11-01

- Class: [Selective serotonin reuptake inhibitors (SSRIs)](https://durgical.com/en/pharmacology/classes/selective-serotonin-reuptake-inhibitors/)
- Transporter: Serotonin transporter (SERT)
- ATC code: N06AB04

⇄**Serotonin transporter (SERT)**Citalopram

ⓘ The figure shows S-citalopram (escitalopram), the active half of citalopram, at the central site of a thermostabilised human SERT (ts3).

**Target in 3D:** Serotonin transporter (SERT). PDB structure 5I71 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/5I71) · Drag to rotate · pinch to zoom

## Mechanism of action

Citalopram is a racemic mixture; its S-enantiomer (escitalopram) blocks the serotonin transporter and gives the antidepressant effect. The drug causes dose-dependent QTc prolongation, which sets its upper dose limit.

- The S-enantiomer of citalopram binds the serotonin transporter
- Serotonin reuptake is blocked
- Serotonin signalling increases and mood improves over weeks
- At higher exposure the QTc interval lengthens

## Pharmacokinetics

**Absorption**
By mouth

**Metabolism**
Mainly in the liver; CYP2C19 poor metabolisers and CYP2C19 inhibitors raise exposure

**Half-life**
Long, allowing steady levels; doubled in liver impairment and longer in older adults

## Indications

- Major depressive disorder in adults

## Adverse effects

### Common

- Ejaculation disorder, mainly delayed ejaculation
- Nausea
- Somnolence or insomnia, fatigue
- Increased sweating

### Serious (rare, important)

- Dose-dependent QTc prolongation, torsades de pointes and sudden death
- Suicidal thoughts and behaviour in young people (boxed warning)
- Serotonin syndrome
- Bleeding
- Hyponatraemia
- Seizures
- Angle-closure glaucoma

## Contraindications

- MAO inhibitors, including linezolid and intravenous methylene blue, or within 14 days of stopping an MAOI
- Pimozide (QT prolongation)
- Hypersensitivity to citalopram
- Avoided in congenital long QT, bradycardia, low potassium or magnesium, recent myocardial infarction, uncompensated heart failure and with other QT-prolonging drugs

## Key interactions

**Cimetidine or other CYP2C19 inhibitors**
Higher citalopram levels and more QT risk

**Class IA or III antiarrhythmics, some antipsychotics and antibiotics**
Additive QT prolongation

**MAO inhibitors and other serotonergic drugs**
Serotonin syndrome

**NSAIDs, aspirin, warfarin**
Higher bleeding risk

## What is monitored

- Potassium and magnesium at baseline in people at risk of electrolyte disturbances
- ECG in people with heart disease or other QT risk factors
- Mood and suicidal thoughts
- Sodium in older adults

## Administration and safety

- Given by mouth
- Low potassium or magnesium is corrected before starting
- Not combined with escitalopram (same active molecule)

## Nursing care

- Ask about palpitations, fainting and heart disease, and review the medicine list for QT-prolonging drugs
- Report dizziness, palpitations or syncope at once
- Assess suicidal thoughts early in treatment and after dose changes
- Teach that abrupt stopping can cause a discontinuation syndrome

## 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.

## Memory aid

CitaloPRAM PRolongs QT: check the ECG, potassium and magnesium.

## Test yourself

Think of the answer, then tap the question to see it.

## Which SSRI is best known for dose-dependent QT prolongation?

Citalopram, which is why the label sets a dose ceiling and advises caution with heart disease and electrolyte problems.

## Which electrolytes are corrected before starting citalopram in a person at risk?

Potassium and magnesium, because low levels increase the risk of QT prolongation and arrhythmia.

## Why does cimetidine increase the risk of citalopram?

Cimetidine inhibits CYP2C19, so citalopram levels rise and the QT interval lengthens more.

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## Related drugs

- [Escitalopram](https://durgical.com/en/pharmacology/escitalopram/)
- [Sertraline](https://durgical.com/en/pharmacology/sertraline/)

[← Back to the class: Selective serotonin reuptake inhibitors (SSRIs)](https://durgical.com/en/pharmacology/classes/selective-serotonin-reuptake-inhibitors/)

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 - CITALOPRAM capsule](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=80af8ae8-c106-4895-bab3-0579b41f1e75) (DailyMed (U.S. National Library of Medicine), 2026); [Citalopram: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a699001.html) (MedlinePlus (U.S. National Library of Medicine), 2025); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=N06AB) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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