Citalopram (Celexa) is an SSRI antidepressant FDA-approved for major depressive disorder in adults. It works by selectively blocking the serotonin transporter (SERT) with minimal effects on other receptors, increasing synaptic serotonin levels. Common side effects include nausea, insomnia, sexual dysfunction, and sweating. The key distinguishing warning is dose-dependent QTc interval prolongation: the FDA caps the maximum dose at 40 mg/day (reduced to 20 mg/day in elderly patients or those taking CYP2C19 inhibitors like omeprazole) due to the risk of serious cardiac arrhythmias.
Citalopram
Uses & FDA Indications
Citalopram is FDA-approved for the treatment of major depressive disorder (MDD) in adults. Unlike sertraline — which carries six separate FDA-approved psychiatric indications — citalopram's label covers depression specifically, making it one of the more narrowly indicated SSRIs despite its widespread clinical use.
Off-label uses are common in clinical practice and include generalized anxiety disorder (GAD), panic disorder, social anxiety disorder, obsessive-compulsive disorder (OCD), and premenstrual dysphoric disorder. Its relatively simple pharmacokinetic profile and low potential for drug-drug interactions (compared to fluoxetine or paroxetine) have made it popular in primary care and in medically complex patients taking multiple medications.
How It Works
Citalopram is a highly selective serotonin reuptake inhibitor. It blocks the serotonin transporter (SERT), preventing the presynaptic neuron from reclaiming serotonin after it has been released into the synapse. This increases the amount and duration of serotonin activity at postsynaptic receptors. Citalopram is the most SERT-selective of the SSRIs with minimal affinity for histaminergic, dopaminergic, adrenergic, or muscarinic receptors, contributing to its relatively clean side-effect profile.
Citalopram is a racemic mixture — it contains equal parts of two mirror-image molecules. The S-enantiomer (escitalopram) is responsible for virtually all of the SERT-inhibiting activity. The R-enantiomer contributes little therapeutically and may actually oppose some of the S-enantiomer's effects at higher concentrations. This is the pharmacological rationale for escitalopram: isolating the active half produces a more selective, potentially more effective compound.
Citalopram has fewer clinically significant CYP450 drug interactions than most other SSRIs. It is a mild inhibitor of CYP2D6 but does not substantially inhibit CYP1A2, CYP3A4, or CYP2C9 at therapeutic levels — making it a preferred option when polypharmacy is a concern.
FDA BLACK BOX WARNING — SUICIDALITY IN YOUTH: Antidepressants increase the risk of suicidal thinking and behavior in children, adolescents, and young adults (under 25) with major depressive disorder and other psychiatric disorders. Monitor closely for worsening depression, agitation, irritability, or suicidal ideation — especially in the first 1–2 months and after dose changes. Citalopram is not approved for use in pediatric patients.
FDA QTc WARNING: Citalopram causes dose-dependent QT interval prolongation. Do not exceed 40 mg/day in most adults. The maximum is 20 mg/day in patients over 60, with hepatic impairment, who are CYP2C19 poor metabolizers, or who take CYP2C19 inhibitors. Avoid in patients with congenital long QT syndrome or in combination with other QT-prolonging drugs.
Side Effects
Common
- Nausea — most common early side effect; typically resolves within 1–2 weeks. Taking with food helps.
- Insomnia or sedation — varies by patient; morning dosing may help with insomnia, evening dosing with sedation.
- Sexual dysfunction — decreased libido, delayed orgasm, anorgasmia. Affects a significant minority of patients and often persists throughout treatment.
- Sweating — can be persistent and socially distressing.
- Dry mouth — common, generally mild.
- Tremor, fatigue, diarrhea
Serious
- QTc prolongation — dose-dependent cardiac conduction change that can predispose to torsades de pointes arrhythmia. This is the defining safety concern distinguishing citalopram from other SSRIs and drove the FDA dose restrictions.
- Serotonin syndrome — rare at monotherapy doses but life-threatening with concurrent serotonergic drugs. Symptoms include fever, agitation, tremor, diarrhea, hyperreflexia.
- Hyponatremia (SIADH) — primarily in elderly patients. Presents with confusion, headache, weakness.
- Bleeding risk — SSRI depletion of platelet serotonin raises bleeding risk, especially combined with NSAIDs or anticoagulants.
Drug Interactions
| Drug / Class | Interaction | Clinical Significance |
|---|---|---|
| MAO Inhibitors (phenelzine, tranylcypromine, selegiline, linezolid, methylene blue) | Combined serotonergic activity can cause potentially fatal serotonin syndrome. A 14-day washout is required between citalopram and classic MAOIs in either direction. | CONTRAINDICATED — absolute |
| Pimozide | Citalopram inhibits CYP2D6, which metabolizes pimozide. Elevated pimozide levels combined with citalopram's own QTc effect dramatically increases arrhythmia risk. | CONTRAINDICATED — absolute |
| QT-prolonging drugs (antipsychotics, certain antibiotics, antiarrhythmics) | Additive QTc prolongation risk. Citalopram already prolongs QT dose-dependently; combination with other QT-prolonging agents multiplies arrhythmia risk. | High — avoid combination; if unavoidable, ECG monitoring required |
| CYP2C19 inhibitors (omeprazole, esomeprazole, cimetidine, fluconazole) | Citalopram is substantially metabolized by CYP2C19. Inhibitors raise citalopram plasma levels, effectively moving patients into a higher-dose exposure category with greater QTc risk. | High — reduce citalopram to 20 mg max when combined |
| Escitalopram (Lexapro) | Citalopram contains escitalopram as its S-enantiomer. Co-administration is pharmacologically equivalent to dose-stacking and dramatically increases serotonergic and QTc risk. | CONTRAINDICATED — never combine |
| NSAIDs / Anticoagulants | SSRI depletion of platelet serotonin plus NSAID inhibition of thromboxane synthesis raises GI bleeding risk approximately 3-fold. | Moderate — consider PPI co-prescription; prefer acetaminophen for analgesia |
| Lithium | Pharmacodynamic synergy raises serotonin syndrome risk. May also enhance therapeutic effect (used as augmentation in treatment-resistant depression). | Moderate — monitor for serotonin syndrome symptoms |
Warnings & Contraindications
Contraindications
- Concomitant use with MAO inhibitors, linezolid, or IV methylene blue
- Concomitant use with pimozide
- Known QT prolongation or congenital long QT syndrome
- Hypersensitivity to citalopram
- Co-administration with escitalopram
QTc Dose Restrictions
The FDA's 2011 safety communication established firm upper limits for citalopram due to dose-dependent QT interval prolongation. These are regulatory ceilings, not dosing recommendations. Patients in higher-risk groups — elderly, hepatic impairment, CYP2C19 poor metabolizers, or those taking CYP2C19 inhibitors — must not exceed 20 mg/day. For all other adults, 40 mg/day is the absolute maximum.
Discontinuation Syndrome
Abrupt discontinuation of citalopram can cause discontinuation syndrome within 1–3 days: "brain zaps," flu-like symptoms, dizziness, irritability, insomnia, and vivid dreams. Always taper gradually under provider guidance, with slower tapers after longer treatment durations.
Check for QT prolongation risk or other interactions involving citalopram.
Check Drug Interactions →Frequently Asked Questions
Is Celexa the same as Lexapro?
Celexa (citalopram) and Lexapro (escitalopram) are closely related but not identical. Citalopram is a racemic mixture of two mirror-image molecules (R- and S-enantiomers). Escitalopram is simply the purified S-enantiomer — the pharmacologically active half. In practical terms, escitalopram is the more selective, cleaner version of citalopram with fewer drug interactions and a better-studied safety profile. The two drugs should never be taken together, as they are essentially the same active compound and co-administration would be equivalent to taking a higher dose of one.
What is the max dose of citalopram?
The FDA limits citalopram to a maximum of 40 mg per day for most adults due to dose-dependent QTc interval prolongation, which can increase the risk of dangerous cardiac arrhythmias. The limit is further reduced to 20 mg per day in elderly patients (over 60), those with liver impairment, CYP2C19 poor metabolizers, and patients taking CYP2C19 inhibitors such as omeprazole or cimetidine. These restrictions were established in a 2011 FDA safety communication and represent a firm regulatory ceiling.
Is citalopram safe for the heart?
At approved doses, citalopram is generally safe for most patients, including those with stable cardiac conditions. However, it carries an FDA warning for dose-dependent QTc prolongation — an electrical change in the heart's rhythm that can predispose to a rare but serious arrhythmia called torsades de pointes. Risk is highest at higher doses and in patients who already have a prolonged QT interval, low potassium or magnesium levels, or who are taking other QT-prolonging medications. Patients with known congenital QT prolongation should avoid citalopram. For patients with cardiac concerns, an EKG before or during treatment is reasonable.