Enhancement of Docetaxel Absorption Using Ritonavir in an Oral Milk-Based Formulation.

OBJECTIVE: The current study aimed to develop a novel milk-based formulation of docetaxel, a sparingly soluble antineoplastic agent, administered so far exclusively by the intravenous route and evaluate its oral bioavailability. METHODS: Pre-formulation studies included the determination of docetaxel solubility in water-alcohol mixtures as well as short-term content uniformity experiments of the final formulation. The pharmacokinetic (PK) performance of the developed milk-based formulations was further evaluated in vivo in mice using ritonavir, a potent P-glycoprotein inhibitor, as an absorption enhancer of docetaxel and the marketed intravenous docetaxel formulation, Taxotere®, as a control. RESULTS: In vivo PK results in mice showed that all the administered oral docetaxel formulations had limited absorption in the absence of ritonavir. On the contrary, ritonavir co-administration given as pre-treatment significantly enhanced oral bioavailability of both the marketed and milk-based docetaxel formulations; an even more marked increase in drug exposure was observed when ritonavir was incorporated within the docetaxel milk-based formulation. The fixed-dose combination also showed a more prolonged absorption of the drug compared to separate administrations. CONCLUSIONS: The current study provides insights for the discovery of a novel milk-based formulation that could potentially serve as an alternative, non-toxic and patient-friendly carrier for an acceptable docetaxel oral chemotherapy.

Development of a joint population pharmacokinetic model of ezetimibe and its conjugated metabolite.

Ezetimibe (EZE) is an extensively used antihyperlipidemic drug with an important cholesterol lowering activity. It undergoes extensive first-pass metabolism to form its active glucuronide metabolite (EZEG). Both drugs exhibit complex pharmacokinetic profiles attributed mainly to repetitive enterohepatic kinetics. The aim of the present study was the investigation of EZE and EZEG pharmacokinetics (PK), through the development of a joint population pharmacokinetic model able to characterize their kinetic processes and enterohepatic recirculation simultaneously. Concentration-time data derived from a bioequivalence study in 28 healthy subjects were used for the analysis. Population PK modeling was performed on the obtained data using nonlinear mixed effect modeling approach, where different methodologies were applied for the description of the complex metabolism and recirculation processes of the two compounds. EZE and EZEG concentrations were best described by a population PK model incorporating first-pass metabolism and an enterohepatic recirculation loop, accounting for the recycling process of the two moieties. This is the first joint population pharmacokinetic model describing the kinetics of both EZE and EZEG.

On the pharmacokinetics of two inhaled budesonide/formoterol combinations in asthma patients using modeling approaches.

Dry powder inhalers containing the budesonide/formoterol combination have currently a well-established position among other inhaled products. Even though their efficacy mainly depends on the local concentrations of the drug they deliver within the lungs, their safety profile is directly related to their total systemic exposure. The aim of the present investigation was to explore the absorption and disposition kinetics of the budesonide/formoterol combination delivered via two different dry powder inhalers in asthma patients. Plasma concentration-time data were obtained from a single-dose, crossover bioequivalence study in asthma patients. Non-compartmental and population compartmental approaches were applied to the available datasets. The non-compartmental analysis allowed for an initial characterization of the primary pharmacokinetic (PK) parameters of the two inhaled drugs and subsequently the bioequivalence assessment of the two different dry powder inhalers. The population pharmacokinetic analysis further explored the complex absorption and disposition characteristics of the two drugs. In case of inhaled FOR, a five-compartment PK model including an enterohepatic re-circulation process was developed. For inhaled BUD, the incorporation of two parallel first-order absorption rate constants (fast and slow) for lung absorption in a two-compartment PK model emphasized the importance of pulmonary anatomical features and underlying physiological processes during model development. The role of potential covariates on the variability of the PK parameters was also investigated.

Population pharmacokinetics of fluticasone propionate/salmeterol using two different dry powder inhalers.

The combination of fluticasone propionate (FLP) and salmeterol (SAL) is often used in clinical practice for the treatment of pulmonary disorders. The purpose of this study was to explore the pharmacokinetics (PK) of inhaled FLP and SAL, after concomitant administration, in healthy male and female subjects using two dry powder inhalers. Plasma concentration (C)-time (t) data were obtained from a single dose, two-sequence, two-period, crossover (2×2) bioequivalence (BE) study. Activated charcoal was co-administered in order to prohibit absorption from the gastrointestinal tract. A number of 60 subjects were recruited, while 57 of them completed the study and were included in the PK analysis. Initially, PK parameters of FLP and SAL were estimated using the classic non-compartmental methods. Subsequently, BE assessment was applied to the estimated PK parameters of the two dry powder inhalers. Special focus was placed on the population PK analysis of the C-t data, which were pooled together. 'Treatment' (i.e., test or reference) and 'period' of the BE study were considered as covariates. A variety of structural and residual error models were tested to find the one which best described the plasma C-t data of FLP and SAL. Demographic data were also evaluated for their impact on the PK parameters. Several goodness-of-fit criteria were utilized. The non-compartmental PK estimates of this study were in agreement with previously reported values. The population PK analysis showed that FLP data were described by a two-compartment model with first-order absorption and elimination kinetics. Body weight was found to affect significantly absorption rate constant, inter-compartmental clearance, and volume of distribution of the peripheral compartment. As body weight increases, the values of these PK parameters also rise. For SAL, the best results were obtained when a two-compartment disposition model was used assuming very rapid absorption kinetics (like intravenous bolus) and first-order elimination kinetics. Gender was found to be a significant covariate on clearance, with men exhibiting higher clearance than women.