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Citalopram (Celexa)

SSRI • Last reviewed 2025-09-26

General information

Citalopram is an SSRI indicated for major depressive disorder. It is valued for minimal drug–drug interactions but carries a dose-dependent QT prolongation warning.

Tablets (10, 20, 40 mg) and an oral solution allow once-daily dosing with or without food. FDA recommends a maximum of 40 mg/day in adults and 20 mg/day in patients ≥60 years, hepatic impairment, or CYP2C19 poor metabolizers.

Compared with other SSRIs, citalopram produces similar remission rates but may be less activating, making it useful in anxious or insomnia-prone patients when dosed at night.

Clinicians should monitor electrolytes and ECG in patients with cardiac disease, bradycardia, or concomitant QT-prolonging medications.

Dosing & administration

Start 20 mg once daily; evaluate response after 4 weeks.

Increase to 40 mg/day if needed and if QT risk is low.

Do not exceed 20 mg/day in patients ≥60 years, hepatic impairment, CYP2C19 poor metabolizers, or taking CYP2C19 inhibitors.

Mechanism of action

Selective inhibition of the serotonin transporter with minimal affinity for muscarinic, histamine, or adrenergic receptors.

Metabolism & pharmacokinetics

Bioavailability ~80%; peak plasma levels 4 hours post-dose. Metabolized hepatically via CYP2C19, CYP3A4, and CYP2D6 to demethylated metabolites. Elimination half-life averages 35 hours (longer in elderly/hepatic impairment).

Drug interactions

Avoid MAOIs, linezolid, or methylene blue (serotonin syndrome).

CYP2C19 inhibitors (omeprazole, fluconazole) raise concentrations; limit to 20 mg/day.

QT-prolonging drugs (antiarrhythmics, antipsychotics) increase arrhythmia risk.

Monitoring & safety checks

  • Assessment of suicidality and activation

  • Serum sodium in older adults

  • Baseline and follow-up ECG in high-risk patients

Discontinuation guidance

Taper over at least 1–2 weeks; discontinuation symptoms are usually mild but may include dizziness, irritability, or paresthesias.

References

  1. Citalopram Prescribing Information — DailyMed
  2. APA Clinical Practice Guideline for Depression (2023)
  3. CANMAT 2024 Depression Guidelines (2024)

Educational use only — verify details in current prescribing information and authoritative clinical guidelines before making prescribing decisions.