Reprocessing Mass Spectra from Therapeutic Drug Monitoring to Unveil Proton Pump Inhibitor Use and Quantify Phenoconversion of Escitalopram Metabolism in CYP2C19-Genotyped Patients.

CYP2C19

Inhibition of CYP2C19 by proton pump inhibitors, producing phenoconversion of escitalopram metabolism

The authors reprocessed high-resolution mass spectra from therapeutic drug monitoring at an Oslo laboratory combining drug assays and pharmacogenetics, in order to detect proton pump inhibitor (PPI) comedication and quantify its effect on escitalopram metabolism. Exact-mass and fragment detection against the mzCloud library identified pantoprazole, esomeprazole/omeprazole or lansoprazole in 445 of 2,818 CYP2C19-genotyped patients (15.8%). The primary outcome was the N-desmethylescitalopram-to-escitalopram metabolic ratio in ultrarapid versus poor metabolizers. This ratio was 4.5-fold higher in ultrarapid than in poor metabolizers without PPIs (P < 0.001), versus 2.8-fold in pantoprazole users (P < 0.001) and 1.8-fold in esomeprazole/omeprazole users (P = 0.2). Esomeprazole and omeprazole thus exert stronger phenoconversion than pantoprazole.

Synthesis written by Geno'X. For the full original abstract, please refer to the source publication.

The result is useful because it quantifies phenoconversion drug by drug: on esomeprazole or omeprazole, the metabolic gap between ultrarapid and poor metabolizers nearly disappears, which explains much of the genotype-phenotype mismatch seen in real-world escitalopram use. The endpoint remains a metabolic biomarker, not a clinical response or an adverse event, and the esomeprazole/omeprazole signal does not reach significance. The approach itself — reprocessing already-acquired spectra to reconstruct comedication — is worth noting: the data already exist in laboratories performing therapeutic drug monitoring.

Analysis by Dr Thibaut Benquey