Population Pharmacokinetic Analysis of a Nevirapine-Based HIV-1 Prevention of Mother-to-Child Transmission Program in Uganda to Assess the Impact of Different Dosing Regimens for Newborns.

Population Pharmacokinetic Analysis of a Nevirapine-Based HIV-1 Prevention of Mother-to-Child Transmission Program in Uganda to Assess the Impact of Different Dosing Regimens for Newborns.

J Clin Pharmacol. 2013 Mar; 53(3): 294-304
Frank M, Harms G, Kunz A, Kloft C

Single-dose nevirapine for mothers and newborns at delivery is the simplest prevention strategy for vertical HIV-1 transmission and hence widely used in resource-constrained settings. HIV-1-positive mothers and newborns received single-dose nevirapine in a prevention of mother-to-child HIV-1 transmission (PMTCT) program in Uganda. In a pharmacokinetic investigation, breast milk and plasma samples of mothers and newborns were collected. The nonlinear mixed-effects modeling approach was suitable for analysis (average: 1.8 samples/matrix/individual). For describing the nevirapine pharmacokinetics in mothers and newborns, a 1-compartment model was demonstrated to be sufficient. The plasma-placenta transfer could be quantified, revealing a transfer fraction of 11% to 25% (with a significant influence of time span between maternal nevirapine intake and birth) and a high transfer rate constant from maternal drug administration. Interindividual variability was moderate between mothers and high between newborns. Simulations revealed that newborns born early (<1 hour) after maternal nevirapine intake would benefit from a 3-fold higher nevirapine dosage (6 mg/kg) after birth for analogous protective plasma concentrations over the first 2 weeks. In contrast, postnatal nevirapine dosage seemed to be dispensable for newborns born late (>24 hours) after maternal nevirapine intake. These dosing recommendations should be evaluated in prospective studies, including additional antiretroviral drugs in accordance with current PMTCT guidelines. HubMed – drug

Race and drug formulation influence on mycophenolic Acid pharmacokinetics in stable renal transplant recipients.

J Clin Pharmacol. 2013 Mar; 53(3): 285-93
Tornatore KM, Sudchada P, Attwood K, Wilding GE, Gundroo AC, Difrancesco R, Gray V, Venuto RC

Limited mycophenolic acid (MPA) data are available comparing racial influence on mycophenolate mofetil (MMF) and enteric-coated mycophenolate sodium (EC-MPS) pharmacokinetics.Intrapatient MPA pharmacokinetics of MMF versus EC-MPS were compared in 13 male African American (AA) and 14 Caucasian (C) renal transplant recipients (RTRs). RTRs were switched to equivalent doses of the alternate formulation for at least 10 days prior to the second study. Mycophenolic acid clearance and dose-normalized area under the concentration-time curve(0-12) (AUC*) were determined. Mixed model statistics evaluated the main effects of race, drug formulation, and interaction of race and drug formulation (R × D) with albumin, cyclosporine trough, renal function, and diabetes and enterhepatic recirculation.Significant R × D was identified for MPA AUC* for EC-MPS (AA, 0.056 ± 0.029 [mg·h/L]/mg; C, 0.080 ± 0.044 [mg·h/L]/mg) compared with MMF (AA, 0.053 ± 0.019 [mg·h/L]/mg; C, 0.060 ± 0.025 [mg·h/L]/mg), P = .022. Significant R × D was identified with albumin in the model for MPA clearance for MMF (AA, 21.7 ± 8.9 L/h; C, 20.5 ± 10.8 L/h) compared with EC-MPS (AA, 22.2 ± 10.1 L/h; C, 16.2 ± 9.1 L/h), P = .032.Race influences MPA exposure between MMF and EC-MPS and may warrant therapeutic monitoring during formulation conversion. HubMed – drug

Variation in prescribing patterns and therapeutic drug monitoring of intravenous busulfan in pediatric hematopoietic cell transplant recipients.

J Clin Pharmacol. 2013 Mar; 53(3): 264-75
McCune JS, Baker KS, Blough DK, Gamis A, Bemer MJ, Kelton-Rehkopf MC, Winter L, Barrett JS

Personalizing intravenous (IV) busulfan doses in children using therapeutic drug monitoring (TDM) is an integral component of hematopoietic cell transplant. The authors sought to characterize initial dosing and TDM of IV busulfan, along with factors associated with busulfan clearance, in 729 children who underwent busulfan TDM from December 2005 to December 2008. The initial IV busulfan dose in children weighing ?12 kg ranged 4.8-fold, with only 19% prescribed the package insert dose of 1.1 mg/kg. In those children weighing >12 kg, the initial dose ranged 5.4-fold, and 79% were prescribed the package insert dose. The initial busulfan dose achieved the target exposure in only 24.3% of children. A wide range of busulfan exposures were targeted for children with the same disease (eg, 39 target busulfan exposures for the 264 children diagnosed with acute myeloid leukemia). Considerable heterogeneity exists regarding when TDM is conducted and the number of pharmacokinetic samples obtained. Busulfan clearance varied by age and dosing frequency but not by underlying disease. The authors- group is currently evaluating how using population pharmacokinetics to optimize initial busulfan dose and TDM (eg, limited sampling schedule in conjunction with maximum a posteriori Bayesian estimation) may affect clinical outcomes in children. HubMed – drug

Evaluation of the Impact of UGT Polymorphism on the Pharmacokinetics and Pharmacodynamics of the Novel PPAR Agonist Sipoglitazar.

J Clin Pharmacol. 2013 Mar; 53(3): 256-63
Stringer F, Ploeger BA, Jongh JD, Scott G, Urquhart R, Karim A, Danhof M

Sipoglitazar is a peroxisome proliferator-activated receptor ?, ?, and ? agonist. During phase I, a wide distribution of clearance between individuals was observed. Hypothesized to result from a polymorphism in the uridine 5′-diphospate-glucuronosyltransferase (UGT)2B15 enzyme, pharmacogenetic samples were collected from each individual for genotyping UGT2B15 in a subsequent phase I trial in healthy subjects (n = 524) and in 2 phase II trials in type 2 diabetes subjects (n = 627), total genotype frequency was as follows: *1/*1 (22%), *1/*2 (51%), and *2/*2 (27%). The impact of genotype on exposure was assessed using a pharmacokinetic modeling approach; the influence of genotype on efficacy was evaluated using 12-week HbA1c change from baseline. Model analysis demonstrated UGT2B15 genotype accounted significantly for the variability in sipoglitazar clearance; however, a small fraction of subjects had a clearance that could not be explained entirely by genotype. HbA1c drop increased with daily drug dose. When stratified by both dose and genotype, HbA1c drop was larger in the UGT2B15*2/*2 compared with UGT2B15*1/*1 and UGT2B15*1/*2 genotypes (P < .05). In summary, UGT2B15 genotype is a strong predictor for sipoglitazar clearance; a greater clinical response observed in the UGT2B15*2/*2 genotype appears to confirm this. However, overlap in individual rates of clearance across genotypes remains after accounting for genotype. HubMed – drug

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