Population pharmacokinetics and pharmacodynamics of zidovudine, didanosine and nevirapine in children and adolescents with advanced HIV disease

• Main Author: Kim, Yong Ho
• Format: Others
• Published: Scholarly Commons 2000
• Subjects: Pharmaceuticals; Health and environmental sciences; Adolescents; Children; Didanosine; HIV; Immune deficiency; Nevirapine; Zidovudine
• Online Access: https://scholarlycommons.pacific.edu/uop_etds/2722; https://scholarlycommons.pacific.edu/cgi/viewcontent.cgi?article=3721&context=uop_etds

The population pharmacokinetics and pharmacodynamics (PK/PD) of nevirapine (NVP), zidovudine (ZDV), and didanosine (ddI) were evaluated in 432 pediatric patients with HIV, randomized to receive either a double-therapy of ZDV + ddI or NVP + ddI; or triple-therapy of NVP + ZDV + ddI as a substudy of the AIDS Clinical Trials Group Protocol 245 in 2 phases. In phase 1, nonlinear mixed-effect modeling (NONMEM) analysis was employed for population pharmacokinetics (PPK) study for ZDV, ddI and NVP. One-compartment model with first-order input and first-order elimination was fitted to the NVP, ZDV and ddI data. Final PPK models were as follows: ZDV; CL (1/hr, without nevirapine coadministration) = 52.4 × BSA, CL (1/hr, with nevirapine coadministration) = 65.0 × BSA, Vd/F(1) = 116 × BSA, ddI; CL (1/hr) = 73.4 × BSA + 69.9, Vd/F(1) = 132, and NVP; CL (1/hr) = 2.30 × BSA, Vd/F(1) = 120. In phase 2, the relationship between the predicted serum concentrations of ZDV, ddI, and NVP and pharmacodynamic responses were evaluated via S-Plus ® exploratory data analysis. No apparent relationship between average steady-state serum concentrations and pharmacodynamic variables, such as HIV-1 RNA(RNA) levels, CD4 + count was found. However, the responses of RNA level and CD4 + count to the double therapy (ddI/NVP) versus triple therapy (ddI/NVP/ZDV) were significantly different after 4 weeks of therapy ( P = 0.0014 for RNA level at week 4, P = 0.0454 for CD4 + count at week 12). No significantly different responses were found in weight changes ( P > 0.25 at all weeks). Also, the maximum drop of RNA level throughout the treatment period had a strong relationship to the decline slope of RNA at week 4 as follows: Maximum drop of RNA = 3.1139 × RNA decline slope at week 4 - 0.411. Nevirapine dosing regimens were compared using simulation via Trial Simulator™. Both ACTG regimen (body surface area based) and manufacture's regimen (age and weight based) produced similar concentrations at lower end concentration but manufacture's regimen produce higher concentration at upper end with 1000 simulated patients (ACTG regimen; 2150, 3827, and 4992 ng/ml, manufacturer's regimen; 2066, 4130, and 6568 ng/ml, for 10 th , 50 th , and 96 th percentile, respectively). It is suggested to use body surface area based dosing regimen for NVP.