- Design
- Retrospective analysis of therapeutic drug monitoring and pharmacogenetic data with mass-spectra reprocessing
- Population
- 2,818 CYP2C19-genotyped escitalopram users in Oslo, Norway, 445 with PPI co-medication
- Primary outcome
- N-desmethylescitalopram to escitalopram metabolic ratio, ultrarapid vs poor metabolisers
- Effect
- 4.5-fold without PPI; 2.8-fold with pantoprazole; 1.8-fold with omeprazole or esomeprazole
Researchers reprocessed high-resolution mass spectra from routine escitalopram monitoring to detect PPIs in the same samples, then compared metabolic ratios across CYP2C19 genotypes.
In people not taking a PPI, genotype separated metabolism clearly. PPIs, which inhibit CYP2C19, compressed that difference. Omeprazole and esomeprazole had a stronger effect than pantoprazole, consistent with their known inhibitory potency.
This is phenoconversion: the patient's functional phenotype no longer matches the genotype on the report. For prescribers, a genotype result is only half the answer; the medicine list is the other half.
- Without PPIs, ultrarapid metabolisers had a 4.5-fold higher metabolic ratio than poor metabolisers.
- With pantoprazole the gap fell to 2.8-fold; with omeprazole or esomeprazole to 1.8-fold.
- About one in six escitalopram users was also taking a PPI.
- Pantoprazole had a weaker effect, so it is the less disruptive choice when a PPI is needed.
- Consider therapeutic drug monitoring when response or tolerability does not match genotype.
Why it matters
Genotype-guided prescribing assumes the genotype predicts exposure, and a common co-medication quietly breaks that link.
Don't overread it
This measured a metabolic ratio, not clinical response or adverse effects.
The statistics, in plain English
The fold-differences describe how much faster ultrarapid metabolisers convert escitalopram than poor metabolisers. The omeprazole comparison was not statistically significant (P = 0.2), likely because few poor metabolisers were in that group.
Read the rest in the app
You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.
Scan to keep reading on your phone. No account needed to start.
Tomorrow morning, before your first patient
One edition a day for clinical pharmacology, written by the desk, every claim tied to its paper. Six minutes.
Get the app — free