Pharmacokinetics of Pantoprazole and CYP2C19 Activity in Children and Adolescents With GERD: A Pilot Study

The World Health Organization has declared childhood obesity to be "one of the most serious public health challenges of the 21st century," (http://www.who.int/dietphysicalactivity/childhood). Given that obese children are generally excluded from clinical trials, little to no information exists regarding the impact of obesity on drug disposition and drug action, creating a gap in physicians' knowledge on how to appropriately select the dose of many critical medications (e.g., anticancer agents), so as to prevent toxicity associated with overdosing, while avoiding the harms of under-treatment. The proposed study will examine the effect of obesity on the metabolism of a commonly used medication, the proton pump inhibitor pantoprazole, by exploring the relationships between age, obesity, basal metabolic rate and genetic control of the enzyme primarily responsible for pantoprazole metabolism. We will also validate a simple breath test that can be used to predict pantoprazole dose requirement for obese children. The study is designed to test the following experimental hypotheses:\[13C\]-pantoprazole pharmacokinetic parameters are not different between non-obese and obese children and adolescents, collectively (both age groups combined) or stratified by age group (SA 1) \[13C\]-pantoprazole pharmacokinetic parameters or DOB values (and thus, CYP2C19 activity) are not different between males and females (SA 1 \& 2) \[13C\]-pantoprazole pharmacokinetic parameters and DOB (Delta over baseline) values (and thus, CYP2C19 activity) are independent of age over the age range of 6 to 17 years (SA 1 \& 2) Obesity does not alter the relative contributions of CYP2C19-dependent and non-CYP2C19-dependent (i.e., CYP3A4) metabolism of pantoprazole, as measured by the urinary ratio of 4-hydroxy-pantoprazole to pantoprazole sulfone (SA 1 \& 2) The \[13C\]-pantoprazole breath test, by determining DOB at discrete time point(s), is a non-invasive measure of CYP2C19 phenotype (SA 2) Clearance