On the Association between Gastrointestinal Symptoms and Extragastric Manifestations.

The aim of this study was to investigate the relationship between gastrointestinal (GI) symptoms and extragastric manifestations such as headache, fatigue, and dizziness. A prospective cohort study was conducted in a tertiary hospital in Athens, where patients with GI problems and extragastric symptoms were treated only for their GI problems, and improvement in extragastric manifestations was recorded. Inclusion criteria were an age older than 18 years, the presence of at least one of the three extragastric symptoms investigated in this study (headache, dizziness, and fatigue), and the concomitant presence of at least one gastrointestinal symptom (e.g., nausea, belching, abdominal tenderness, epigastric pain, halitosis, flatulence, diarrhea, bad odor of flatulence, flatulence, and constipation). A standardized questionnaire was used to collect demographic data (such as age, weight, and height), patients' symptoms, laboratory findings (gastric biopsy, gastroscopy, and colonoscopy), and intensity/frequency of GI and extragastric symptoms. Statistically significant associations were found between GI symptoms (nausea, constipation, halitosis, and belching) and dizziness, fatigue, and headache (frequency, intensity, and duration). Treatment of GI problems resulted in a significant improvement in extragastric symptoms within one month of treatment initiation. It should be emphasized that the actual reason for the improvement in extragastric symptoms was solely the resolution of the GI problems, as patients did not receive specific treatments for headache, dizziness or fatigue, or other changes in daily life. This study demonstrates the association between extragastric manifestations and GI disorders.

Osteoporosis treatment with risedronate: a population pharmacokinetic model for the description of its absorption and low plasma levels.

To develop a population pharmacokinetic model that describes the absorption and low plasma levels of risedronate in the body. The impact of patients' characteristics on risedronate kinetics is investigated. Simulations revealed the high variability in the concentration levels after different dosage schemes. No dosage adjustment is required in renal impairment. INTRODUCTION: Risedronate exhibits very low plasma levels and high residence time in the body. The aim of this study is to describe and explain the risedronate transit through the body. The impact of volunteers' characteristics on the kinetics of risedronate is also investigated. Simulations are used to compare the risedronate plasma levels after different dosage schemes and assess the need for dose adjustment in patients with impaired kidney functionality. METHODS: Plasma concentration-time data were obtained from a four-period, two sequence, single-dose, crossover bioequivalence study. The effects of several covariates (e.g., weight, albumin, creatinine, alkaline phosphatase, and calcium) on model parameters were tested. Non-linear mixed-effect modeling was applied and a variety of models were evaluated placing emphasis on absorption and disposition properties. The modeling and simulation work was implemented in MonolixTM 2020R1. RESULTS: Following oral administration, the kinetics of risedronate was best described by a two-compartment model with lag time, first-order absorption, and elimination. The extent of peripheral distribution (i.e., bones) was found to be remarkably high. No volunteer characteristics were identified to affect significantly the disposition of risedronate. Using simulations, risedronate plasma profiles were obtained for different doses and frequencies of administration. CONCLUSION: The absorption and disposition kinetics of risedronate were successfully characterized. Simulations revealed the high discrepancy in the concentration levels observed after different dosage regimens, implying the safety profile of risedronate. In virtual patients with renal impairment, the blood levels of risedronate are increased, but not in an extent requiring dose adaptation.

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.

From Bioequivalence to Biosimilarity: The Rise of a Novel Regulatory Framework.

One of the most crucial issues in pharmacotherapy is to address the query if a patient can be switched from one product to another of the same active substance. For the conventional small-molecule drugs, there is a consensus on the required bioequivalence criteria. However, proving equivalence in the field of biologicals is an issue with no clear harmony. The aim of this review is to highlight the differences between the biologicals and the conventional chemical drugs, as well as, to present the different regulatory requirements for the placement of biosimilars on the market.Biologicals are substantially larger than chemical compounds, their manufacturing process is very complex, and their protein structure may trigger immune reactions. For this reason, the conventional bioequivalence approach is not adequate, but further emphasis should be placed on the quality of the manufacturing process and the risks of immunogenicity. The assessment procedure of biosimilars should encompass their comparison with the innovator product using all available evidence derived from the development process. The latter includes analytical and animal studies, pharmacokinetic and pharmacodynamic data, as well as, clinical trials focusing on immunogenicity. The US FDA has established a step-wise approach to demonstrate biosimilarity, while the EMA has already issued many guidelines referring either to all biosimilars or to specific products/classes. Overall, a case-by-case assessment procedure is considered by the regulatory authorities. In any case the placement of a biosimilar on the market does not necessarily imply interchangeability with the innovator drug.

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.

Fractal volume of drug distribution: it scales proportionally to body mass.

PURPOSE: To develop the physiologically sound concept of fractal volume of drug distribution, vf, and evaluate its utility and applicability in interspecies pharmacokinetic scaling. METHODS: Estimates for vf of various drugs in different species were obtained from the relationship: vf = (v - Vpl)(Vap - Vpl)/V + Vpl where v is the total volume of the species (equivalent to its total mass assuming a uniform density Ig/mL), Vpl is the plasma volume of the species and Vap is the conventional volume of drug distribution. This equation was also used to calculate the fractal analogs of various volume terms of drug distribution (the volume of central compartment, Vc, the steady state volume of distribution, Vss, and the volume of distribution following pseudodistribution equilibrium, Vz). The calculated fractal volumes of drug distribution were correlated with body mass of different mammalian species and allometric exponents and coefficients were determined. RESULTS: The calculated values of vf for selected drugs in humans provided meaningful and physiologically sound estimates for the distribution of drugs in the human body. For all fractal volume terms utilized, the allometric exponents were found to be either one or close to unity. The estimates of the allometric coefficients were found to be in the interval (0,1). These decimal values correspond to a fixed fraction of the fractal volume term relative to body mass in each one of the species. CONCLUSIONS: Fractal volumes of drug distribution scale proportionally to mass. This confirms the theoretically expected relationship between volume and mass in mammalian species.