Comparison of non-compartmental and mixed effect modelling methods for establishing bioequivalence for the case of two compartment kinetics and censored concentrations

Comparison of Compartmental and Non-Compartmental Analysis to Detect Biopharmaceutical Similarity of Intravenous Nanomaterial-Based Rifabutin Formulations

Pharmacometric analysis is often used to quantify the differences and similarities between formulation prototypes. In the regulatory framework, it plays a significant role in the evaluation of bioequivalence. While non-compartmental analysis provides an unbiased data evaluation, mechanistic compartmental models such as the physiologically-based nanocarrier biopharmaceutics model promise improved sensitivity and resolution for the underlying causes of inequivalence. In the present investigation, both techniques were applied to two nanomaterial-based formulations for intravenous injection, namely, albumin-stabilized rifabutin nanoparticles and rifabutin-loaded PLGA nanoparticles. The antibiotic rifabutin holds great potential for the treatment of severe and acute infections of patients co-infected with human immunodeficiency virus and tuberculosis. The formulations differ significantly in their formulation and material attributes, resulting in an altered biodistribution pattern as confirmed in a biodistribution study in rats. The albumin-stabilized delivery system further undergoes a dose-dependent change in particle size which leads to a small yet significant change in the in vivo performance. A second analysis was conducted comparing the dose fraction-scaled pharmacokinetic profiles of three dose levels of albumin-stabilized rifabutin nanoparticles. The dose strength affects both the nanomaterial-related absorption and biodistribution of the carrier as well as the drug-related distribution and elimination parameters, increasing the background noise and difficulty of detecting inequivalence. Depending on the pharmacokinetic parameter (e.g., AUC, C_max, Cl_obs), the relative (percentage) difference from the average observed using non-compartmental modeling ranged from 85% to 5.2%. A change in the formulation type (PLGA nanoparticles vs. albumin-stabilized rifabutin nanoparticles) resulted in a similar level of inequivalence as compared to a change in the dose strength. A mechanistic compartmental analysis using the physiologically-based nanocarrier biopharmaceutics model led to an average difference of 152.46% between the two formulation prototypes. Albumin-stabilized rifabutin nanoparticles tested at different dose levels led to a 128.30% difference, potentially due to changes in particle size. A comparison of different dose strengths of PLGA nanoparticles, on average, led to a 3.87% difference. This study impressively illustrates the superior sensitivity of mechanistic compartmental analysis when dealing with nanomedicines.

Determination of the Pharmacokinetics and Tissue Distribution of Methyl 3,4-Dihydroxybenzoate (MDHB) in Mice Using Liquid Chromatography-Tandem Mass Spectrometry

BACKGROUND AND OBJECTIVES

Methyl 3,4-dihydroxybenzoate (MDHB) has the potential to prevent neurodegenerative diseases (NDDs). The present work aims to reveal the pharmacokinetics and tissue distribution characteristics of MDHB.

METHODS

The pharmacokinetics and tissue distribution of MDHB were analyzed using LC-MS/MS after a single intragastric administration (50 to 450 mg/kg) in mice, and samples were collected from five animals at specific time points.

RESULTS

Pharmacokinetic parameters of MDHB following intragastric administrations were: the time to peak concentration (T_max) ranged from 0.033 to 0.07 h, the peak concentration (C_max) ranged from 12,379.158 to 109798.712 μg/l, the elimination half-life (t_1/2z) ranged from 0.153 to 1.291 h, the area under the curve (AUC_0-∞) ranged from 640.654 to 20,241.081 μg/l × h, the mean residence time (MRT_0-∞) ranged from 0.071 to 0.206 h, the apparent volume of distribution (V_z/F) ranged from 17.538 to 45.244 l/kg, and the systemic clearance (Cl_z/F) ranged from 22.541 to 80.807 l/h/kg. The oral bioavailability of MDHB was 23%. The maximum MDHB content was detected in the stomach, and the minimum content was observed in the testes; the peak content in the brain was 15,666.93 ng/g.

CONCLUSIONS

The pharmacokinetic characteristics of MDHB include fast absorption, high systemic clearance, a short half-life and an oral bioavailability of 23%. Additionally, MDHB permeates the blood-brain barrier (BBB) and is rapidly distributed to all organs. The identification of the pharmacokinetics of MDHB following its oral administration will contribute to further preclinical and clinical studies of its effects.

Utilization of data below the analytical limit of quantitation in pharmacokinetic analysis and modeling: promoting interdisciplinary debate

Traditionally, bioanalytical laboratories do not report actual concentrations for samples with results below the LOQ (BLQ) in pharmacokinetic studies. BLQ values are outside the method calibration range established during validation and no data are available to support the reliability of these values. However, ignoring BLQ data can contribute to bias and imprecision in model-based pharmacokinetic analyses. From this perspective, routine use of BLQ data would be advantageous. We would like to initiate an interdisciplinary debate on this important topic by summarizing the current concepts and use of BLQ data by regulators, pharmacometricians and bioanalysts. Through introducing the limit of detection and evaluating its variability, BLQ data could be released and utilized appropriately for pharmacokinetic research.