Antimalarial therapy during pregnancy poses important safety concerns due to potential teratogenicity and maternal physiological and biochemical changes during gestation. Piperaquine (PQ) has gained interest for use in pregnancy in response to increasing resistance towards sulfadoxine-pyrimethamine in sub-Saharan Africa. Coinfection with HIV is common in many developing countries, however, little is known about the impact of antiretroviral (ARV) mediated drug-drug interaction (DDI) on piperaquine pharmacokinetics during pregnancy. This study applied mechanistic pharmacokinetic modelling to predict pharmacokinetics in non-pregnant and pregnant patients, which was validated in distinct customised population groups from Thailand, Sudan and Papua New Guinea. In each population group, no significant differences in day 7 concentrations were observed during different gestational weeks (GW) (weeks 10-40), supporting the notion that piperaquine is safe throughout pregnancy with consistent pharmacokinetics, although possible teratogenicity may limit this. Antiretroviral-mediated DDIs (efavirenz and ritonavir) had moderate effects on piperaquine during different gestational weeks with a predicted AUC in the range 0.56-0.8 and 1.64-1.79 for efavirenz and ritonavir, respectively, over GW 10-40, with a reduction in circulating human serum albumin significantly reducing the number of subjects attaining the day 7 (post-dose) therapeutic efficacy concentrations under both efavirenz and ritonavir DDIs. This present model successfully mechanistically predicted the pharmacokinetics of piperaquine in pregnancy to be unchanged with respect to non-pregnant women, in the light of factors such as malaria/HIV co-infection. However, antiretroviral-mediated DDIs could significantly alter piperaquine pharmacokinetics. Further model refinement will include collation of relevant physiological and biochemical alterations common to HIV/malaria patients.

Inter‐ethnic variability in pharmacokinetics (PK) has been attributed to several factors ranging from genetic to environmental. It is not clear how current teaching in higher education (HE) reflects what published literature suggests on this subject. This study aims to gain insights into current knowledge about inter‐ethnic differences in PK based on reports from published literature and current teaching practices in HE. A systematic literature search was conducted on PubMed and Scopus to identify suitable literature to be reviewed. Insights into inter‐ethnic differences in PK teaching among educators in HE and industry were determined using a questionnaire. Thirty‐one percent of the studies reviewed reported inter‐ethnic differences in PK, of these, 37% of authors suggested genetic polymorphism as possible explanation for the inter‐ethnic differences observed. Other factors authors proposed included diet and weight differences between ethnicities. Most respondents (80%) who taught inter‐ethnic difference in PK attributed inter‐ethnic differences to genetic polymorphism. While genetic polymorphism is one source of variability in PK, the teaching of genetic polymorphism is better associated with interindividual variabilities rather than inter‐ethnic differences in PK as there are no genes with PK implications specific to any one ethnic group. Nongenetic factors such as diet, weight, and environmental factors, should be highlighted as potential sources of interindividual variation in the PK of drugs.

The insidious nature of Zika virus (ZIKV) infections can have a devastating consequence for fetal development. Recent reports have highlighted that chloroquine (CQ) is capable of inhibiting ZIKV endocytosis in brain cells. We applied pharmacokinetic modeling to develop a predictive model for CQ exposure to identify an optimal maternal/fetal dosing regimen to prevent ZIKV endocytosis in brain cells. Model validation used 13 nonpregnancy and 3 pregnancy clinical studies, and a therapeutic CQ plasma window of 0.3-2 mM was derived. Dosing regimens used in rheumatoid arthritis, systemic lupus erythematosus, and malaria were assessed for their ability to target this window. Dosing regimen identified that weekly doses used in malaria were not sufficient to reach the lower therapeutic window; however, daily doses of 150 mg achieved this therapeutic window. The impact of gestational age was further assessed and culminated in a final proposed regimen of 600 mg on day 1, 300 mg on day 2 and 3, and 150 mg thereafter until the end of trimester 2, which resulted in maintaining 65% and 94% of subjects with a trough plasma concentration above the lower therapeutic window on day 6 and at term, respectively.

The fixed dosed combination of artemether and lumefantrine (AL) is widely used for the treatment of malaria in adults and children in sub-Sahara Africa, with lumefantrine day 7 concentrations being widely used as a marker for clinical efficacy. Both are substrates for CYP3A4 and susceptible to drug-drug interactions (DDIs); indeed, knowledge of the impact of these factors is currently sparse in paediatric population groups. Confounding malaria treatment is the co-infection of patients with tuberculosis. The concomitant treatment of AL with tuberculosis chemotherapy, which includes the CYP3A4 inducer rifampicin, increases the risk of parasite recrudescence and malaria treatment failure. This study developed a population-based PBPK model for AL in adults capable of predicting the pharmacokinetics of AL under non-DDI and DDI conditions, as well as predicting AL pharmacokinetics in paediatrics of 2-12years of age. The validated model was utilised to assess the concomitant treatment of rifampicin and lumefantrine under standard body-weight based treatment regimens for 2-5year olds, and demonstrated that no subjects attained the target day 7 concentration (C) of 280ng/mL, highlighting the importance of this DDI and the potential risk of malaria-TB based DDIs. An adapted 7-day treatment regimen was simulated and resulted in 63% and 74.5% of subjects attaining the target C for 1-tablet and 2-tablet regimens respectively.

Ivermectin has demonstrated many successes in the treatment of a range of nematode infections. Considering the increase in malaria resistance, attention has turned toward ivermectin as a candidate for repurposing for malaria. This study developed and validated an ivermectin physiology-based pharmacokinetic model in healthy adults (20-50 years), pediatric (3-5 years/15-25 kg) subjects, and a representative adult malaria population group (Thailand). Dosing optimization demonstrating a twice-daily dose for 3- or 5-day regimens would provide a time above the LC50 of more than 7 days for adult and pediatric subjects. Furthermore, to address the occurrence of CYP450 induction that is often encountered with antiretroviral agents, simulated drug-drug interaction studies with efavirenz highlighted that a 1-mg/kg once-daily dose for 5 days would counteract the increased ivermectin hepatic clearance and enable a time above LC50 of 138.8 h in adults and 141.2 h in pediatric subjects. It was also demonstrated that dosage regimen design would require consideration of the age-weight geographical relationship of the subjects, with a dosage regimen for a representative Thailand population group requiring at least a single daily dose for 5 days to maintain ivermectin plasma concentrations and a time above LC50 similar to that in healthy adults.