Teresa Dalla Costa

Nanoencapsulation increases quinine antimalarial efficacy against Plasmodium berghei in vivo.

The aims of this work were to develop quinine (QN)-loaded nanocapsules, to evaluate their efficacy in vivo and to determine their pharmacokinetics and erythrocyte partition coefficient. Plasmodium berghei-infected Wistar rats were used to evaluate the efficacy of QN-loaded nanocapsules using different dosing regimens. Pharmacokinetics was evaluated after intravenous administration of free or nanoencapsulated QN (25 mg/kg) to infected rats. The QN partition coefficient into P. berghei-infected erythrocytes was evaluated. QN-loaded nanocapsules presented an adequate particle size (176 nm), narrow particle distribution (0.19), negative zeta potential (-18 mV) and high drug content and encapsulation efficiency. Intravenous administration of QN-loaded nanocapsules at 75 mg/kg/day to infected rats resulted in 100% survival, representing an almost 30% reduction compared with the free QN effective dose (105 mg/kg/day). The pharmacokinetic parameters of nanoencapsulated QN were not significantly different from those determined for free drug (alpha=0.05). The QN partition coefficient into infected erythrocytes doubled (6.25+/-0.25) when the drug was nanoencapsulated compared with the free drug (3.03+/-0.07). Therefore, nanoencapsulation increased the interaction between QN and the erythrocyte and this mechanism is responsible for the drugs increased efficacy when nanoencapsulated.

Penetration of Cefaclor Into the Interstitial Space Fluid of Skeletal Muscle and Lung Tissue in Rats

AbstractPurpose. To measure and compare the penetration of cefaclor from the plasma compartment into the interstitial space of lung and skeletal muscle in rats and to integrate the data in a pharmacokinetic model. Methods. Unbound interstitial concentrations in muscle and lung were measured by in vivo microdialysis following i.v. bolus doses of 50 and 75 mg/kg cefaclor. Unbound muscle concentrations were also measured after a primed, continuous i.v. infusion at an infusion rate of 0.3 mg/kg/min. Results. The cefaclor half-life in plasma, muscle and lung was approximately 1 h. Unbound cefaclor concentrations in muscle and lung were found to be virtually identical. A 2-compartment body model was fitted to the data with a tissue penetration factor (AUCtissue(unbound)/AUCplasma(unbound)) of approximately 0.26 independent of dose, tissue and mode of administration. Conclusions. Unbound concentrations of cefaclor in the interstitial space fluid of lung and skeletal muscle are of similar magnitude and lower than those in plasma. Using total plasma concentrations would overestimate the antibacterial activity of the drug and therefore its clinical efficacy. Instead, therapeutically active levels of cefaclor at the site of action should be taken into account. Microdialysis allows direct measurement of these unbound concentrations.

Lipid-core nanocapsules restrained the indomethacin ethyl ester hydrolysis in the gastrointestinal lumen and wall acting as mucoadhesive reservoirs.

The aim of this work was to investigate if the indomethacin ethyl ester (IndOEt) released from lipid-core nanocapsules (NC) is converted into indomethacin (IndOH) in the intestine lumen, intestine wall or after the particles reach the blood stream. NC-IndOEt had monomodal size distribution (242 nm; PDI 0.2) and zeta potential of -11 mV. The everted rat gut sac model showed IndOEt passage of 0.16 micromol m(-2) through the serosal fluid (30 min). From 15 to 120 min, the IndOEt concentrations in the tissue increased from 6.13 to 27.47 micromol m(-2). No IndOH was formed ex vivo. A fluorescent-NC formulation was used to determine the copolymer bioadhesion (0.012 micromol m(-2)). After NC-IndOEt oral administration to rats, IndOEt and IndOH were detected in the gastrointestinal tract (contents and tissues). In the tissues, the IndOEt concentrations decreased from 459 to 5 microg g(-1) after scrapping, demonstrating the NC mucoadhesion. In plasma (peripheric and portal vein), in spleen and liver, exclusively IndOH was detected. In conclusion, after oral dosing of NC-IndOEt, IndOEt is converted into IndOH in the intestinal lumen and wall before reaching the blood stream. The complexity of a living system was not predicted by the ex vivo gut sac model.

Role of Microdialysis in Pharmacokinetics and Pharmacodynamics: Current Status and Future Directions

Diagnostic and therapeutic decisions in medical practice are still generally based on blood concentrations of drugs and/or biomolecules despite the knowledge that biochemical events and pharmacological effects usually take place in tissue rather than in the bloodstream. Microdialysis is a semi-invasive technique that is able to measure concentrations of the free, active drug or endogenous compounds in almost all human tissues and organs. It is currently being used to monitor brain metabolic processes and quantify tissue biomarkers, and determine transdermal drug distribution and tissue pharmacokinetics, confirming its importance as a widely used sampling technique in clinical drug monitoring and drug development as well as therapy and disease follow-up, contributing to rationalizing drug dosing regimens and influencing the clinical decision-making process.

Determination and confirmation of chloramphenicol in honey, fish and prawns by liquid chromatography–tandem mass spectrometry with minimum sample preparation: validation according to 2002/657/EC Directive

A reliable, simple and sensitive liquid chromatography–electrospray ionisation-tandem mass spectrometry (LC–ESI-MS/MS) confirmation method has been developed for chloramphenicol (CAP) determination in honey, fish and prawns. For honey, samples were extracted with ethyl acetate, an aliquot was evaporated to dryness and re-dissolved in mobile phase. For fish and prawns, tissues were extracted with acetonitrile and chloroform. The organic layer was evaporated to dryness and the residue was re-constituted with water: acetonitrile (90:10). LC separation was achieved on a C18 column with gradient elution using a mobile phase of acetonitrile and water. Analysis was carried out on a triple–quadrupole tandem mass spectrometer in multiple reaction monitoring (MRM) mode via electrospray interface operated in negative ionisation mode, with deuterated chloramphenicol-d5 (d5-CAP) as internal standard. Method validation was performed according to the criteria of Commission Decision 2002/657/EC. Four identification points were obtained for CAP with one precursor ion and two product ions. The limit of detection (LOD) was 0.02 µg kg−1. Linear calibration curves were obtained over concentration ranges of 0.1–1.0 µg kg−1 in tissues. Mean recoveries ranged from 85.5% to 115.6%, with the corresponding intra- and inter-day variation ranging from 1.0% to 22.5%, depending on matrix type and level of concentration. The decision limit (CCα) and detection capability (CCβ) of the method were obtained for all matrices: 0.04 and 0.06 µg kg−1, respectively, for prawns and fish and 0.05 and 0.09 µg kg−1 for honey.

Nanostructure-coated diclofenac-loaded microparticles: preparation, morphological characterization, in vitro release and in vivo gastrointestinal tolerance

This work reports the preparation and characterization of polymeric nanostructure-coated diclofenac-loaded microparticles. After spray-drying, powders presented 80% of yield and encapsulation efficiency of 83%. SEM analyses showed nanostructures adsorbed onto the surface of microparticles presenting surface area (BET) and pore volumes (BJH) (83 m2 g-1, 0.10 cm3 g-1) smaller than the uncoated-core (163 m2 g-1, 0.25 cm3 g-1). In vitro drug release experiments at pH 5.0 and 7.4 showed dissolution efficiencies of 34% and 78% (uncoated-core), 74% and 83% (physical mixture of raw materials), and 58% and 85% (nanostructure-coated microparticles), respectively. Mathematical modeling of the dissolution profiles fitted a biexponential model at pH 5.0 and a monoexponential model at pH 7.4. Regarding the digestive tolerance experiments, the total lesional indexes were 156.1 ± 48.5 for sodium diclofenac aqueous solution, 132.4 ± 45.7 for uncoated-core, 109.1 ± 35.8 for physical mixture and 29.9 ± 12.1 for microparticles showing a protective effect of these microparticles against the mucosal diclofenac damage. This strategy of coating presents a potential use for oral administration of drugs.

Pharmacokinetic evaluation of LASSBio-579: an N-phenylpiperazine antipsychotic prototype

This work aimed to investigate the pharmacokinetics of the N‐phenylpiperazine antipsychotic prototype LASSBio‐579 and to compare the results with those described for its bioisosteric derivative LASSBio‐581. LASSBio‐579 was administered to male Wistar rats as a 10 mg kg−1 intravenous bolus and 30 and 60 mg kg−1 intraperitoneal and 60 mg kg−1 oral doses, and plasma concentrations were determined by a validated LC‐MS/MS method. Individual plasma concentration‐time profiles were evaluated by non‐compartmental and compartmental analysis, using WinNonlin. LASSBio‐579 plasma protein binding was 93 ± 4%. After intravenous administration of 10 mg kg−1, the Vdss (0.6 ± 0.2 L kg−1) and the t1/2 (5.2 ± 1.1 h) determined were smaller than those obtained after extravascular routes, but the CLtot (0.23 ± 0.05 Lh−1 kg−1) was statistically similar (α = 0.05). The intraperitoneal and oral bioavailability was around 1.7% and 0.6%, respectively. The plasma profiles obtained after intravenous and intraperitoneal administration of the compound were best fitted to a three‐compartment and two‐compartment lag‐time open model, respectively. Brain tissue showed low penetration (6.3%) and t1/2 of 1.1 h. Both the limited bioavailability and the lower brain penetration of LASSBio‐579, in comparison with the LASSBio‐581, suggest that its CNS activity may be due to a high receptor binding affinity or to a specific distribution into brain structures.

Preclinical pharmacokinetic and pharmacodynamic evaluation of thiazolidinone PG15: an anti‐inflammatory candidate

Objectives Novel 5‐benzilidene thiazolidinones have been synthesized and exhibited anti‐inflammatory activity. In this work one of the compounds of the thiazolidinone chemical series, (5Z,E)‐3‐[2‐(4‐chlorophenyl)‐2‐oxoethyl]‐5‐(1H‐indol‐3‐ ylmethylene)‐thiazolidine‐2,4‐dione (PG15) was investigated aiming to determine the drugs anti‐inflammatory potential in pre‐clinical studies.

Phase II trial and pharmacokinetic study of thalidomide in patients with metastatic colorectal cancer

Introduction. This study was designed to estimate the percentage of objective tumor responses, toxicity profile, and obtain additional information about the plasma pharmacokinetics of thalidomide in patients with refractory and progressing metastatic colorectal cancer. Study design. This phase II clinical trial was conducted according to the two-stage Simon method with the inclusion of consecutive patients. The study protocol was approved by the Institutional Review Board (IRB) of the Academic Hospital (HCPA) of the Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil. Patients and methods. Seventeen patients with previously treated, refractory progressive metastatic colorectal cancer were eligible. Six patients had prior radiotherapy. The patients had a median of one previous chemotherapy regimen. Patients were initially treated with 200 mg/day of thalidomide with an increase in dose by 200 mg/day every 2 weeks until a final daily dose of 800 mg/day was achieved. Patients were evaluated every 8 weeks for response by radiographic criteria. Plasma pharmacokinetics studies were performed in four patients at 200 mg level and in one patient at 600 mg during the first 24 h. Main outcome measures and results. A total of 17 patients were accrued, all of them being evaluable for toxicity and 14 for response. Thalidomide was well tolerated, with constipation, somnolence, dizziness, and dry mouth being the major toxicities. There were no objective response or stable disease. The median survival was 3.6 months. Single-agent thalidomide is a generally well-tolerated drug that showed no antitumor activity in patients with advanced pretreated metastatic colorectal cancer. Although thalidomide did not show antitumor activity in this patient population, future studies of this agent in patients at initial stages of the disease (when its antiangiogenic properties may be more relevant to disease progression) could be considered.

Determination of chloramphenicol, thiamphenicol, florfenicol and florfenicol amine in poultry, swine, bovine and fish by liquid chromatography-tandem mass spectrometry

A simple, rapid and sensitive method for confirmatory and quantitative purposes using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) was developed and validated for determination of chloramphenicol, thiamphenicol, florfenicol and its metabolite, florfenicol amine, in poultry, swine, bovine and fish muscle. Sample preparation was based on extraction with organic solvent (ethyl acetate: ammonium hydroxide, 98:2) followed by evaporation and fat removal using hexane. The chromatographic separation was carried out with an XTerra C18 column with a gradient elution using water and acetonitrile both with 2mM of ammonium acetate. Mass spectrometry with electrospray ionization was operated in positive or negative polarity using selected-reaction monitoring (SRM) analysis mode, achieving the requirements of four identification points for each compound. Chloramphenicol-D5 was added as internal standard. Method validation was performed according to the criteria of Commission Decision 2002/657/EC. Parameters as precision, reproducibility, trueness, CCα and CCβ were determined. Trueness values were within the range 82-108% and 84-111% for bovine and fish, respectively. Precision ranged from 1.1% to 10.1% and within-laboratory reproducibility ranged from 4.3 to 18.1%, depending on matrix. The CCα and CCβ for bovine muscle, for instance, were established as 0.06 and 0.11μgkg(-1), respectively. The method was successfully applied for several interlaboratory proficiency testing programs, achieving 100% of satisfactory results.