Escitalopram and citalopram: the antidepressants with the clearest gene link
Antidepressant pharmacogenomics is the most oversold corner of consumer genetics, which is a shame, because for these two drugs there is a real, well-evidenced gene effect underneath the marketing.
This page also covers citalopram: CPIC publishes one recommendation for both, so the guidance below applies to either drug.
Also sold as: Cipralex, Lexapro, Cipramil, Celexa.
What escitalopram and citalopram are
Escitalopram and citalopram are SSRIs, prescribed for depression and for several anxiety disorders. They are closely related: escitalopram is the active half of citalopram, isolated and sold on its own. CPIC treats them together and publishes a single recommendation covering both, which is why one page here covers both drugs rather than two near-identical ones.
Why your genes come into it
CYP2C19 clears these drugs out of the body, and how fast it does that sets the blood level a given dose produces. Slow metabolizers accumulate more drug and are likelier to run into the dose-related side effects that make people abandon an SSRI in the first weeks. At the other end, rapid and ultrarapid metabolizers clear the drug quickly enough that a standard dose may not reach a level that helps, which reads clinically as the drug simply not working. Both ends have published guidance, and both are common enough to matter across a caseload.
What published guidance says
The rows below restate CPIC's published guidance for each possible CYP2C19 result, and they are worth reading for what they are not: none of them says this drug will work for you. They adjust starting dose, titration speed and whether an alternative is worth considering. Antidepressants take weeks to judge, stopping one abruptly can cause discontinuation symptoms, and none of that should be self-directed.
CYP2C19
| If your CYP2C19 result is | What that means | Published CPIC guidance |
|---|---|---|
| Intermediate Metabolizer | Reduced metabolism when compared to CYP2C19 normal metabolizers. Higher plasma concentrations may increase the probability of side effects. | Per CPIC (A): "Initiate therapy with recommended starting dose. Consider a slower titration schedule and lower maintenance dose than normal metabolizers." |
| Likely Intermediate Metabolizer | Reduced metabolism when compared to CYP2C19 normal metabolizers. Higher plasma concentrations may increase the probability of side effects. | Per CPIC (A): "Initiate therapy with recommended starting dose. Consider a slower titration schedule and lower maintenance dose than normal metabolizers." |
| Likely Poor Metabolizer | Reduced metabolism of citalopram and escitalopram to less active compounds when compared to CYP2C19 normal and intermediate metabolizers. Higher plasma concentrations may increase the probability of side effects. | Per CPIC (A): "Consider a clinically appropriate antidepressant not predominantly metabolized by CYP2C19. If citalopram or escitalopram are clinically appropriate, consider a lower starting dose, slower titration schedule and 50% reduction of the standard maintenance dose as compared to normal metabolizers." |
| Normal Metabolizer | Normal metabolism | Per CPIC (A): "Initiate therapy with recommended starting dose" |
| Poor Metabolizer | Reduced metabolism of citalopram and escitalopram to less active compounds when compared to CYP2C19 normal and intermediate metabolizers. Higher plasma concentrations may increase the probability of side effects. | Per CPIC (A): "Consider a clinically appropriate antidepressant not predominantly metabolized by CYP2C19. If citalopram or escitalopram are clinically appropriate, consider a lower starting dose, slower titration schedule and 50% reduction of the standard maintenance dose as compared to normal metabolizers." |
| Rapid Metabolizer | Increase in metabolism of citalopram and escitalopram to less active compounds when compared to CYP2C19 normal metabolizers. Lower plasma concentrations decrease the probability of clinical benefit. | Per CPIC (A): "Initiate therapy with recommended starting dose. If patient does not adequately respond to recommended maintenance dosing, consider titrating to a higher maintenance dose or switching to a clinically appropriate alternative antidepressant not predominantly metabolized by CYP2C19." |
| Ultrarapid Metabolizer | Increased metabolism of citalopram and escitalopram to less active compounds when compared to CYP2C19 rapid and normal metabolizers. Lower plasma concentrations decrease the probability of clinical benefit. | Per CPIC (A): "Consider a clinically appropriate alternative antidepressant not predominantly metabolized by CYP2C19. If citalopram or escitalopram are clinically appropriate, and adequate efficacy is not achieved at standard maintenance dosing, consider titrating to a higher maintenance dose." |
Can your DNA file answer this?
CYP2C19 is one of the pharmacogenes a consumer chip file can genuinely answer, so this is one of the more useful questions to bring to an existing 23andMe or AncestryDNA export. The common reduced-function *2 and increased-function *17 alleles are single positions that consumer arrays generally carry. Rarer alleles are not, and will read as reference; if a defining position is missing from your file, the report says the genotype is unconfirmed rather than assuming the common result. Where the star alleles do not resolve, the answer is Indeterminate.
A genotyping chip reads only a few hundred thousand pre-selected positions, about 0.02% of your genome, chosen for common variation. It does not sequence the rest, so it cannot find the rare or novel pathogenic variants the clinical and carrier modules look for: a “no finding” from chip data means “this chip never looked”, far more so than with whole-genome sequencing. Chip data suits common-variant traits, pharmacogenomic tag SNPs, and haplogroup ancestry, not clinical or carrier screening.
Common questions
Will this tell me which antidepressant will work for me?
No, and any service that says otherwise is overselling. Pharmacogenomic guidance for antidepressants adjusts dose and titration, and flags when a drug cleared by a particular enzyme is a poor structural fit. It does not predict whether a given drug will lift your mood, because response depends on far more than clearance. Treat it as one input among several, not as a matching service.
Why are escitalopram and citalopram on the same page?
Because CPIC publishes one recommendation covering both, and their guidance text is identical. Splitting them would produce two pages saying the same thing, which is worse for a reader and dishonest about how much distinct information exists. The site checks this automatically: if CPIC ever gives the two drugs different guidance, the page fails its own test and the pair gets separated.
I had bad side effects on escitalopram. Would this have predicted it?
Possibly, if you are a poor or likely-poor metabolizer, since that is exactly the group where levels run high on a standard dose. But side effects happen across every metabolizer group, and a normal result would not have meant a smooth ride. What the result offers going forward is a reason to start lower or titrate more slowly, which is a conversation to have rather than a conclusion.
Does CYP2D6 matter for these two as well?
Not for escitalopram and citalopram specifically. CPIC's antidepressant guidance covers several genes across the class, and CYP2D6 carries weight for other SSRIs and for the tricyclics. For these two, CYP2C19 is the gene with the guidance attached, which is what the table above restates.