Makonnen,Eyasu(PhD)Aklillu, Eleni (PhD)Sileshi,Tesemma2025-08-122025-08-122024-04https://etd.aau.edu.et/handle/123456789/6379Introduction: Tuberculosis (TB) is an ancient disease of mankind and remains a major public health problem despite tremendous efforts made to combat it. Globally, 10.6 million people fell ill and 1.13 million died from TB in 2022. Short-course regimens of first-line anti-TB drugs can cure about 90% of cases. However, the success of treatment appears to be on a declining trend over time. Unfavorable TB treatment outcomes might result from altered plasma exposure to antitubercular drugs. Rifampicin and isoniazid display wide between-patient pharmacokinetics variability. Ethiopia is among the 20 high TB and TB-HIV burdens countries. Ethiopians display significant genetic variation from other black African populations. Despite these facts, data on the extent of exposure to rifampicin and isoniazid, as well as inter-patient variability in plasma concentration, remains scarce among Ethiopian TB patients. Objective: The study aimed to determine the plasma levels of rifampicin and isoniazid and investigate the effect of genetic polymorphism and socio-demographic characteristics on the pharmacokinetics of rifampicin and isoniazid in Ethiopian tuberculosis patients. Methods: The study was conducted at the primary healthcare centers in Addis Ababa, Ethiopia. A total of one hundred forty-six adult patients with newly diagnosed TB who had received 2 weeks of first-line anti-TB therapy were enrolled. Venous blood samples were drawn at three- time points from the majority of the patients ranging from 1 to 7 h post-drug intake. Genotyping of NAT2, SLCO1B1 (c.388A>G, c.521T>C), ABCB1 (c.3435C>T, c.4036A>G), AADACc.841G>A, and CES-2 (c.269-965A>G) was done using TaqMan drug metabolism assay. Rifampicin, isoniazid, and its metabolite concentration were determined using validated liquid chromatography-tandem mass spectrometry (LC-MS/MS). Population pharmacokinetic (POPPK) modeling of rifampicin was done using NONMEM. Results: The overall median isoniazid maximum plasma concentration (Cmax) was 4.73 μg/mL and the area under the curve (AUC0-7h) was 11.21μg.h/mL. The majority of patients 94(64.4%) had isoniazid Cmax within the recommended therapeutic range (3-6 μg/mL), while only 19 (13%) had an isoniazid Cmax of below 3 μg/mL. The median rifampicin Cmax was 6.79μg/mL. Only 42 IV | P a g e (29%) patients achieved the therapeutic efficacy threshold (> 8μg/mL). The median rifampicin AUC0-7h was 17.055μg.h/mL. The frequency of slow, intermediate, and fast NAT2 acetylators genotypes was 74.2%, 22.4%, and 3.3%, respectively. The overall concordance between NAT2 genotype and phenotype was 85%. The minor allele frequency for SLCO1B1*1B (c.388A>G), SLCO1B1*5 (c.521T>C), ABCB1 c.3435C>T, ABCB1 c.4036A>G, AADAC c.841G>A and CES-2 c.269-965A>G were 2.2%, 20.2%, 24.4%, 14.6%, 86.1% and 30.6%, respectively. NAT2 acetylator genotypes alone accounted for 26.1% and 40.6% of the variability in isoniazid Cmax and AUC0-7h, respectively. ABCB1 c.4036A>G genotypes independently accounted for 7.4%, and 6.1 % of the variability in rifampicin Cmax and AUC0-7h, respectively. A two-compartment model coupled with a transit absorption model adequately fitted the rifampicin data. Subjects with ABCB1 c.4036A>G GG genotype were estimated to have 41% lower intrinsic clearance of rifampicin compared to subjects with ABCB1 c.4036A>G AA or AG genotypes. Similarly, subjects with ABCB13435C TT genotype were estimated to have a 100% higher absorption rate constant than those with ABCB1 3435C>T CC or CT genotypes. Conclusion: There is high inter-patient variability in isoniazid and rifampicin exposure in Ethiopian TB patients. The majority of the patients attained therapeutic plasma concentration of isoniazid but not that of rifampicin. NAT2 acetylation genotypes, dose, and sex are strong predictors of isoniazid exposure. Rifampicin exposure varied with sex, dose, ABCB1 c.4036A>G, and ADAC c.841G>A genotypes. The clinical significance of higher isoniazid and lower rifampicin exposure in Ethiopian TB patients needs further investigation.en-USRifampicinisoniazidpharmacokineticspharmacogeneticsEthiopiaTuberculosisThesis