Core Chemical Difference
Citalopram is a racemic mixture containing two mirror-image molecules (enantiomers): R-citalopram and S-citalopram. Escitalopram is the purified S-citalopram enantiomer, the active form responsible for most antidepressant effects. This makes escitalopram essentially the refined, single-isomer version of citalopram [1][2].
How This Affects Effectiveness and Dosing
Escitalopram works more selectively on serotonin reuptake, often requiring lower doses for similar results—typically 10-20 mg daily versus citalopram's 20-40 mg. Clinical studies show escitalopram may have a slight edge in response rates for major depression (e.g., 50-60% remission vs. 40-50% for citalopram) and faster onset, though differences are modest [2][3].
Side Effects Comparison
Both cause similar issues like nausea, insomnia, sexual dysfunction, and fatigue, but escitalopram tends to produce fewer due to the absence of less active R-citalopram, which may contribute to QT prolongation (heart rhythm risk). Citalopram carries a stronger FDA warning for doses over 40 mg increasing arrhythmia risk; escitalopram's max is 20 mg with lower cardiac concerns [1][4].
Which Lasts Longer on the Market?
Citalopram launched first (1989 in Europe, 1998 in US as Celexa), with generics widely available since 2004. Escitalopram (Lexapro) followed in 2002 as a patented single-enantiomer upgrade, gaining generic status in 2012. Citalopram patents expired earlier, leading to broader generic competition [1][5].
Cost and Availability Today
Generics make both inexpensive ($10-30/month without insurance), but escitalopram's simpler profile sometimes sways prescribers toward it despite similar pricing. No major supply issues for either [2].
When to Choose One Over the Other
Doctors often start with escitalopram for its potency and tolerability, especially in elderly patients or those with heart risks. Citalopram suits budget-conscious cases or when higher doses are tolerated. Switching between them requires dose adjustment—e.g., 20 mg citalopram ≈ 10 mg escitalopram [3][4].
Sources
[1]: FDA Label: Celexa (citalopram)
[2]: FDA Label: Lexapro (escitalopram)
[3]: Burke et al., 2002, J Clin Psychiatry (escitalopram vs citalopram trial)
[4]: Drugs.com: Citalopram vs Escitalopram
[5]: DrugPatentWatch: Escitalopram Patents