How are Celexa (citalopram) and Lexapro (escitalopram) similar?

Celexa and Lexapro: Key Similarities

Celexa (citalopram) and Lexapro (escitalopram) are fundamentally related medications—Lexapro is the purified active component (S-enantiomer) of Celexa, making them share the same core mechanism of action as selective serotonin reuptake inhibitors (SSRIs). 1

Pharmacological Relationship

Citalopram is a racemic mixture containing equal parts of two mirror-image molecules (R- and S-enantiomers), while escitalopram consists solely of the therapeutically active S-enantiomer 2, 3. This means:

• Both medications work by selectively inhibiting serotonin reuptake at the serotonin transporter protein
• They share the same therapeutic mechanism for treating depression and anxiety disorders
• Escitalopram represents the active portion of citalopram, which is why they should never be co-administered 1

Shared Clinical Indications

Both medications are FDA-approved and guideline-recommended for:

• Major depressive disorder (MDD)
• Generalized anxiety disorder
• Other anxiety-related conditions 4, 5

Common Adverse Effect Profile

Both medications share nearly identical side effect profiles 5:

• Common adverse effects: Nausea, diarrhea, insomnia, sexual dysfunction (approximately 40% incidence), headache, somnolence
• QT prolongation risk: Both carry FDA boxed warnings about dose-dependent QT prolongation and risk of Torsade de Pointes 5
  • Citalopram: Maximum 40 mg/day (20 mg/day if >60 years old)
  • Escitalopram: Also associated with QT prolongation, though typically at higher equivalent doses
• Serotonin syndrome risk: Both contraindicated with MAOIs and require caution with other serotonergic drugs 4, 1
• Bleeding risk: Both increase gastrointestinal bleeding risk, especially with concurrent NSAIDs or anticoagulants 5
• Suicidality: Both carry warnings about increased suicidal thoughts in patients under 24 years old 5, 1

Drug Interaction Profile

Citalopram and escitalopram have the most favorable drug interaction profile among SSRIs 4:

• Minimal CYP450 enzyme effects compared to other SSRIs like fluoxetine, paroxetine, or fluvoxamine
• Lower propensity for drug-drug interactions
• Both interact with QT-prolonging medications
• Both contraindicated with MAOIs (require 14-day washout period)

Discontinuation Considerations

Unlike paroxetine, fluvoxamine, and sertraline, neither citalopram nor escitalopram are strongly associated with discontinuation syndrome 4. However, gradual tapering is still recommended when stopping either medication 1.

Pregnancy and Breastfeeding

Both medications:

• Transfer into breast milk in low concentrations 5
• Have been associated with potential adverse effects in breastfed infants (irritability, decreased feeding) in case reports 5
• Carry similar pregnancy considerations regarding persistent pulmonary hypertension of the newborn (PPHN) when used after 20 weeks gestation 5

Clinical Equivalence Context

Important caveat: While they share these similarities, escitalopram has demonstrated superior efficacy to citalopram at equivalent S-enantiomer doses in some studies 3, 6, likely because the R-enantiomer in citalopram may counteract the S-enantiomer's activity. However, when comparing standard clinical doses (citalopram 20-40 mg vs escitalopram 10-20 mg), efficacy appears comparable 7.

The key practical similarity is that both are first-line SSRI options with favorable tolerability profiles, minimal drug interactions, and shared mechanisms of action, adverse effects, and clinical applications 5.