Browsing by Author "Mukonzo, Jackson K."

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    CYP2B6 genotype-based efavirenz dose recommendations during rifampicin-based antituberculosis cotreatment for a sub-Saharan Africa population
    (Future Medicine Ltd: Pharmacogenomics, 2016) Mukonzo, Jackson K.; Bisaso, Ronald K.; Ogwal-Okeng, Jasper; Gustafsson, Lars L.; Owen, Joel S.; Aklillu, Eleni.
    To assess genotype effect on efavirenz (EFV) pharmacokinetics, treatment outcomes and provide genotype-based EFV doses recommendations during for tuberculosis (TB)-HIV-1 cotreatment. Materials & methods: EFV concentrations from 158 HIV-TB co-infected patients treated with EFV/lamivudine/zidovidine and rifampicin were analyzed. Genotype and CD4 and viral load data were analyzed using a population PK model. Results: Simulated AUCs for 600 mg EFV dose were 1.2- and 2.4-times greater than the product label for Ugandans in general and CYP2B6*6/*6 genotypes respectively. EFV daily doses of 450 and 250 mg for Ugandans and CYP2B6*6/*6 genotypes, respectively, yielded simulated exposures comparable to the product label. Conclusions: Around 450 and 250 mg daily doses might meet EFV dosing needs of HIV-TB infected Ugandans in general and CYP2B6*6/*6 genotypes, respectively.
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    A novel polymorphism in ABCB1 gene, CYP2B6*6 and sex predict single-dose efavirenz population pharmacokinetics in Ugandans.
    (British Journal of Clinical Pharmacology, 2009) Mukonzo, Jackson K.; Röshammar, Daniel; Waako, Paul J; Andersson, Maria; Fukasawa, Takashi; Milani, Lili; Svensson, Jan Olof; Ogwal-Okeng, Jasper; Gustafsson, Lars L; Aklillu, Eleni
    AIMS Efavirenz exhibits pharmacokinetic variability causing varied clinical response. The aim was to develop an integrated population pharmacokinetic/pharmacogenetic model and investigate the impact of genetic variations, sex, demographic and biochemical variables on single-dose efavirenz pharmacokinetics among Ugandan subjects, using NONMEM. METHODS Efavirenz plasma concentrations (n = 402) from 121 healthy subjects were quantified by high-performance liquid chromatography. Subjects were genotyped for 30 single nucleotide polymorphisms (SNPs), of which six were novel SNPs in CYP2B6, CYP3A5 and ABCB1. The efavirenz pharmacokinetics was described by a two-compartment model with zero- followed by first-order absorption. RESULTS Apparent oral clearance (95% confidence interval) was 4 l h l-1 (3.5, 4.5) in extensive metabolizers. In the final model, incorporating multiple covariates, statistical significance was found only for CYP2B6*6 and CYP2B6*11 on apparent oral clearance as well as ABCB1 (rs3842) on the relative bioavailability. Subjects homozygous for CYP2B6*6 (G516T, A785G) and *11 displayed 21 and 20% lower apparent oral clearance, respectively. Efavirenz relative bioavailability was 26% higher in subjects homozygous for ABCB1 (rs3842). The apparent peripheral volume of distribution was twofold higher in women compared with men. CONCLUSIONS The model identified the four factors CYP2B6*6, CYP2B6*11, a novel variant allele in ABCB1 (rs3842) and sex as major predictors of efavirenz plasma exposure in a healthy Ugandan population after single-dose administration. Use of mixed-effects modelling allowed the analysis and integration of multiple pharmacogenetic and demographic covariates in a pharmacokinetic population model.