Scaling of pharmacokinetics in peds

From: "Bonate, Peter" - pbonate@ilexonc.com Subject:[NMusers] Scaling of pharmacokinetics in peds Date: 12/17/2003 12:27 PM Hello everyone. I know we have have this conversation in the past. I am modeling some pharmacokinetic data in kids. I think it was pretty much agreed in those earlier discussions that weight should be built into the structural model a priori. Everyone also pretty much also agreed that weight should go on CL and Q with fixed power 0.7 and weight on volume terms with fixed power 1.0. So here is my question. Clearance for the drug I am modeling is dose-dependent. I wanted to get some opinions on what I am doing. Without any immediate knowledge I am assuming that Km does not change with weight, but Vmax does. So what do you think, should the power term on Vmax be estimated or treated as fixed at 0.7? I am treating it as estimable. If it is anywhere near 0.7, I will make it fixed to 0.7. Any thoughts? Does this seem reasonable. Thanks, Pete Peter L. Bonate, PhD, FCP Director, Pharmacokinetics ILEX Oncology, Inc 4545 Horizon Hill Blvd San Antonio, TX 78229 phone: 210-949-8662 fax: 210-949-8219 email: pbonate@ilexonc.com