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Prior to dolutegravir availability, ritonavir-boosted lopinavir (LPV/r) was an alternative recommendation when first-line drugs could not be used. A high concentration of protease inhibitors was observed in the Thai people living with HIV (PLWH). Thus, dose reduction of LPV/r may be possible. However, the pharmacokinetics and dose optimization of LPV/r have never been investigated. This study aimed to develop a population pharmacokinetic model of LPV/r and provide dosage optimization in Thai PLWH.LPV and RTV trough concentrations from Thai PLWH were combined with intensive data. The data were analyzed by the nonlinear mixed-effects modeling approach. The influence of RTV concentration on LPV oral clearance (CL/F) was investigated.Rifampicin (RIF) use increased LPV and RTV CL/F by 2.16-fold and 1.99-fold, respectively. The reduced dose of 300/75 and 200/150 mg twice daily provided a comparable percentage of patients achieving LPV target trough concentration to the standard dose for PI-naïve patients. For HIV/TB co-infected patients receiving RIF who could not tolerate the recommended dose, the reduced dose of 600/150 mg twice daily was recommended.The population pharmacokinetic model was developed by integrating the interaction between LPV and RTV. The reduced LPV/r dosage offers sufficient LPV exposure for Thai PLWH.

This study aimed to identify factors that significantly influence the pharmacokinetics of voriconazole in Thai adults with hematologic diseases, and to determine optimal voriconazole dosing regimens. Blood samples were collected at steady state in 65 patients (237 concentrations) who were taking voriconazole to prevent or treat invasive aspergillosis. The data were analyzed using a nonlinear mixed-effects modeling approach. Monte Carlo simulation was applied to optimize dosage regimens. Data were fitted with the one-compartment model with first-order absorption and elimination. The apparent oral clearance (CL/F) was 3.43 L/h, the apparent volume of distribution (V/F) was 47.6 L, and the absorption rate constant (Ka) was fixed at 1.1 h&minus, 1. Albumin and omeprazole &ge, 40 mg/day were found to significantly influence CL/F. The simulation produced the following recommended maintenance doses of voriconazole: 50, 100, and 200 mg every 12 h for albumin levels of 1.5&ndash, 3, 3.01&ndash, 4, and 4.01&ndash, 4.5 g/dL, respectively, in patients who receive omeprazole &le, 20 mg/day. Patients who receive omeprazole &ge, 40 mg/day and who have serum albumin level 1.5&ndash, 3 and 3.01&ndash, 4.5 g/dL should receive voriconazole 50 and 100 mg, every 12 h, respectively. Albumin level and omeprazole dosage should be carefully considered when determining the appropriate dosage of voriconazole in Thai patients.

Purpose Efavirenz exhibits high interindividual variability in plasma concentrations, leading to unpredictable efficacy and toxicity. Polymorphism of CYP2B6 516G > T has been found to predominantly contribute to efavirenz variability. However, dosage recommendations incorporating CYP2B6 516G > T polymorphism have not been investigated in the Thai population. This study aimed to develop a population model of the pharmacokinetic properties of efavirenz, and to investigate the impact of patients' characteristics and CYP2B6 516G > T polymorphism on the pharmacokinetic properties of efavirenz. Model-based simulations were performed to provide genotype-based dosage optimization in a Thai population. Methods Plasma efavirenz concentrations measured at 12 h post-dose in 360 Thai HIV-infected patients with and without tuberculosis were analyzed by the nonlinear mixed-effects modeling approach. A 1-compartment model with first-order absorption and elimination was used for describing the pharmacokinetic properties of efavirenz. Findings The allele frequency of CYP2B6 516G > T was 34.17%. The efavirenz oral clearance were 11.9, 8.0, and 2.8 L/h in patients weighing 57 kg and having the CYP2B6 516 GG, 516 GT, and 516 TT genotypes, respectively. The use of rifampicin increased efavirenz oral clearance by 28%. The results from the simulations suggest that efavirenz dosages of 400, 300, and 100 mg once daily in Thai HIV mono-infected patients, and 800, 600, and 200 mg once daily in HIV/tuberculosis co-infected patients carrying CYP2B6 516 GG, 516 GT, and 516 TT, respectively. Implication The results from this study provide a rationale for efavirenz dose adjustment based on CYP2B6 516G > T polymorphism in Thai HIV-infected patients, which could help to improve treatment outcomes in this population. ClinicalTrials.gov identifier: NCT01138267 .