Lexapro (escitalopram) and Celexa (citalopram) are closely related antidepressants, but they’re not the same drug. Lexapro is actually a purified version of one active component found inside Celexa. That single chemical difference affects their dosing, potency, and in some cases, how well they work.
How the Two Drugs Are Related
Citalopram, the active ingredient in Celexa, is a mixture of two mirror-image molecules. Think of them like a left hand and a right hand: identical in structure but impossible to overlap perfectly. In pharmacology, these mirror-image pairs are called enantiomers. Celexa contains both the S-enantiomer and the R-enantiomer in equal amounts.
When researchers studied these two halves separately, they found that the S-enantiomer is more than 100 times more potent at blocking serotonin reuptake than the R-enantiomer. In other words, roughly two-thirds of the citalopram circulating in your blood after taking Celexa is the R-form, which does very little as an antidepressant. Lexapro isolates only the active S-enantiomer, which is why its generic name is escitalopram (the “es” stands for S-enantiomer).
Dosing and Potency
Because Lexapro contains only the active half, you need about half the milligrams to get the same effect. Typical Lexapro doses range from 10 to 20 mg per day, while Celexa doses range from 20 to 40 mg per day. Pooled data from three clinical trials confirmed that citalopram at 20 to 40 mg per day and escitalopram at 10 to 20 mg per day produce equivalent improvements in depression scores over six weeks.
Celexa has a stricter dose ceiling. The FDA capped the maximum at 40 mg per day due to concerns about heart rhythm changes at higher doses. For adults over 60 or people with liver problems, the cap drops further to 20 mg per day. Lexapro doesn’t carry the same restriction, though its maximum recommended dose is 20 mg.
What Each Drug Is Approved to Treat
Both medications are FDA-approved for major depressive disorder in adults. Lexapro has an additional approval for generalized anxiety disorder, which Celexa does not. That doesn’t mean Celexa can’t help with anxiety (doctors frequently prescribe it off-label for that purpose), but Lexapro is the only one of the two that went through formal FDA review for that indication.
Lexapro also has approval for treating major depression in adolescents aged 12 to 17. Celexa does not have a pediatric approval.
Effectiveness in Head-to-Head Studies
A meta-analysis combining eight randomized controlled trials found that Lexapro outperformed Celexa by a modest but statistically significant margin. About 72% of people on escitalopram responded to treatment, compared with 64% on citalopram. The gap was wider for full remission: 62% with escitalopram versus 44% with citalopram across four trials.
These numbers don’t mean Celexa is a poor antidepressant. Both drugs work, and many people do well on either one. But on a population level, Lexapro consistently edges ahead, likely because every milligram is the active form rather than a 50/50 mix.
Side Effects
The side effect profiles overlap almost completely because the drugs share the same mechanism. Common effects for both include nausea, drowsiness, dry mouth, increased sweating, and sexual side effects like reduced libido or difficulty reaching orgasm. Pooled trial data show that tolerability is roughly equivalent at standard doses.
The notable safety difference involves heart rhythm. Citalopram can cause a dose-dependent prolongation of the QT interval, a measure of electrical activity in the heart that, when stretched too far, raises the risk of dangerous arrhythmias. This is why the FDA imposed the 40 mg ceiling for Celexa and recommends avoiding it entirely in people with certain heart conditions, abnormal electrolyte levels, or those already taking other medications that affect the QT interval. Escitalopram carries a lower risk at its approved doses, partly because effective doses are smaller.
How Long They Stay in Your System
Celexa has a longer elimination half-life of about 35 hours, compared to roughly 25 hours for Lexapro. Both are processed through the same liver enzymes (primarily CYP3A4 and CYP2C19). In practical terms, the difference in half-life is unlikely to change your daily experience much, since both are taken once a day. But the longer half-life of Celexa may mean a slightly more gradual tapering process if you stop taking it.
Neither drug is a major player in drug interactions. Both are negligible inhibitors of most liver enzymes, meaning they’re unlikely to significantly raise or lower the levels of other medications you’re taking. They weakly inhibit CYP2D6, but not enough to cause clinically meaningful problems in most cases.
Cost and Availability
Both drugs have been available as generics for years. Citalopram went generic first and has historically been cheaper, though the price gap has narrowed considerably. Generic escitalopram is now widely available and affordable at most pharmacies. If cost is a factor, it’s worth checking prices at your specific pharmacy, since they can vary.
Which One Is Typically Preferred
Lexapro has largely overtaken Celexa in prescribing trends. The combination of slightly better efficacy data, the additional anxiety approval, the pediatric indication, and fewer cardiac concerns at standard doses gives prescribers more reasons to reach for escitalopram. That said, plenty of people are stable and doing well on Celexa, and switching for its own sake isn’t necessary. If Celexa is working for you without issues, the clinical difference between the two may not justify a change.
For someone starting treatment fresh, escitalopram is the more common first choice. For someone already on citalopram who wants to switch, the conversion is straightforward: 20 mg of Celexa roughly corresponds to 10 mg of Lexapro.