2022-09-262022-09-262022https://doi.org/10.1111/cts.13232https://repository.tcu.edu/handle/116099117/55749The 13C-pantoprazole breath test (PAN-BT) is a safe, noninvasive, in vivo CYP2C19 phenotyping probe for adults. Our objective was to evaluate PAN-BT performance in children, with a focus on discriminating individuals who, according to guidelines from the Clinical Pharmacology Implementation Consortium (CPIC), would benefit from starting dose escalation versus reduction for proton pump inhibitors (PPIs). Children (n = 65, 6–17 years) genotyped for CYP2C19 variants *2, *3, *4, and *17 received a single oral dose of 13C-pantoprazole. Plasma concentrations of pantoprazole and its metabolites, and changes in exhaled 13CO2 (termed delta-over-baseline or DOB), were measured 10 times over 8 h using high performance liquid chromatography with ultraviolet detection and spectrophotometry, respectively. Pharmacokinetic parameters of interest were generated and DOB features derived using feature engineering for the first 180 min postadministration. DOB features, age, sex, and obesity status were used to run bootstrap analysis at each timepoint (Ti) independently. For each iteration, stratified samples were drawn based on genotype prevalence in the original cohort. A random forest was trained, and predictive performance of PAN-BT was evaluated. Strong discriminating ability for CYP2C19 intermediate versus normal/rapid metabolizer phenotype was noted at DOBT30 min (mean sensitivity: 0.522, specificity: 0.784), with consistent model outperformance over a random or a stratified classifier approach at each timepoint (p < 0.001). With additional refinement and investigation, the test could become a useful and convenient dosing tool in clinic to help identify children who would benefit most from PPI dose escalation versus dose reduction, in accordance with CPIC guidelines. © 2022 The Authors. Clinical and Translational Science published by Wiley Periodicals LLC on behalf of American Society for Clinical Pharmacology and Therapeutics.https://creativecommons.org/licenses/by-nc-nd/4.0/cytochrome P450 2C19drug metabolitepantoprazolepantoprazole c 13radiopharmaceutical agentunclassified drug2 [[(2 pyridyl)methyl]sulfinyl]benzimidazole derivativeCYP2C19 protein, humancytochrome P450 2C19pantoprazoleproton pump inhibitoradolescentage distributionarea under the curveArticlebootstrappingbreath analysischildcohort analysiscontrolled studydrug blood leveldrug clearancedrug dose escalationdrug dose reductionfemalegastroesophageal refluxgenetic variabilitygenotypehigh performance liquid chromatographyhumanmajor clinical studymaleobesitypantoprazole c 13 breath testpatient selectionphenotypepractice guidelineprevalenceprospective studyrandom forestsex differencesingle drug dosespectrophotometryultraviolet spectroscopyadultgeneticsmetabolismprocedures2-PyridinylmethylsulfinylbenzimidazolesAdultBreath TestsChildCytochrome P-450 CYP2C19GenotypeHumansPantoprazoleProton Pump InhibitorsArticleCC BY-NC-ND 4.0