Population Pharmacokinetics of Lumefantrine in Pregnant and Nonpregnant Women With Uncomplicated Plasmodium falciparum Malaria in Uganda.

Pregnancy alters the pharmacokinetic properties of many antimalarial compounds. The objective of this study was to evaluate the pharmacokinetic properties of lumefantrine in pregnant and nonpregnant women with uncomplicated Plasmodium falciparum malaria in Uganda after a standard fixed oral artemether-lumefantrine treatment. Dense venous (n = 26) and sparse capillary (n = 90) lumefantrine samples were drawn from pregnant patients. A total of 17 nonpregnant women contributed with dense venous lumefantrine samples. Lumefantrine pharmacokinetics was best described by a flexible absorption model with multiphasic disposition. Pregnancy and body temperature had a significant impact on the pharmacokinetic properties of lumefantrine. Simulations from the final model indicated 27% lower day 7 concentrations in pregnant women compared with nonpregnant women and a decreased median time of 0.92 and 0.42 days above previously defined critical concentration cutoff values (280 and 175 ng/ml, respectively). The standard artemether-lumefantrine dose regimen in P. falciparum malaria may need reevaluation in nonimmune pregnant women.CPT: Pharmacometrics & Systems Pharmacology (2013) 2, e83; doi:10.1038/psp.2013.59; advance online publication 13 November 2013.

Dosing rationale for fixed-dose combinations in children: shooting from the hip?

In this investigation we evaluate the relevance of a model-based approach for pharmacokinetic (PK) bridging and dose selection of drug combinations in children. The fixed-dose combination of atovaquone (ATV) and proguanil (PGN) was used for illustration purposes. A population PK model was developed for each compound using plasma concentration data from adult and pediatric patients. PK parameter estimates were subsequently used to simulate drug exposure in children treated with different dose levels of these drugs. We show that, contrary to common practice, different dose ratios may be required across age groups in order to achieve target exposure levels comparable to adults. This example illustrates the effects of covariate interactions, specifically the ones involving body weight (BW) and ethnicity, on the PK of drugs. A model-based approach is critical for dose selection and the rational use of drug combinations in children. Flexible rather than fixed-dose ratios may be needed to ensure comparable target exposure in bridging studies.