Bibiana Verlindo de Araújo

Development and characterization of parenteral nanoemulsions containing thalidomide.

This study reports the development of nanoemulsions intended for intravenous administration of thalidomide (THD). The formulations were prepared by spontaneous emulsification method and optimized with respect to thalidomide (0.01-0.05%, w/w), and hydrophilic emulsifier (polysorbate 80; 0.5-4.0%, w/w) content. The formulations were evaluated concerning physical appearance and drug crystallization; droplet size; zeta potential and drug assay. Only the formulation containing 0.01% THD and 0.5% polysorbate kept its properties in a satisfactory range over the evaluated period (60 days), i.e. droplet size around 200nm, drug content around 95% and zeta potential around -30mV. The transmission electron microscopy revealed emulsion droplets almost spherical in shape confirming the results obtained by photon correlation spectroscopy. Drug crystallization observed for higher content (THD 0.05%, w/w) nanoemulsions was investigated. The crystals observed at optical microscopy presented a different crystal habit compared to that of the raw material used. It was speculated whether the kind of THD polymorph employed could influence nanoemulsion formulation. Formulations were prepared with either one of THD polymorphs (β- or α-) and crystals were characterized by fourier transformed infrared spectroscopy (FTIR) and X-ray diffraction (XRD). It was observed that regardless of the polymorph employed (β- or α-), drug crystallization occurs in the α-form. THD solubility in oils was not influenced by the polymorphic form. In addition, the in vitro dissolution profile of the selected formulation (THD 0.01%, w/w; polysorbate 0.5%, w/w) was assessed by bulk-equilibrium reverse dialysis sac technique and demonstrated a release profile similar to that of a THD acetonitrile solution, with around 95% THD being dissolved within 4h. Finally, a pharmacokinetic simulation of an intravenous infusion of 250mL of the selected nanoemulsion suggests that the parenteral administration of a dose as low as 25mg might lead to therapeutic plasma concentrations of thalidomide.

Free renal levels of voriconazole determined by microdialysis in healthy and Candida sp.-infected Wistar rats

The aims of this study were to evaluate free levels of voriconazole (VCZ) in the kidney of healthy and Candida albicans- or Candida krusei-infected Wistar rats using microdialysis and to establish the relationship between free renal and free plasma levels in both conditions. VCZ (40mg/kg or 60mg/kg) was administered orally (n=6 per group) and blood and microdialysate samples were collected at predetermined time points up to 18h. The mean area under the total concentration-time curve (AUC(0-infinity)) in healthy animals increased from 44.2+/-7.3microg/h/mL to 78.8+/-4.0microg/h/mL for plasma and from 15.1+/-2.4microg/h/mL to 27.9+/-2.6microg/h/mL for tissue after 40mg/kg and 60mg/kg VCZ dosing, respectively, showing non-linear pharmacokinetics described by a one-compartment model with Michaelis-Menten elimination. There were no statistical differences between the AUC(0-infinity) of plasma and tissue for either healthy or infected groups for the same dose. The antifungal tissue penetration was similar for both doses and all conditions investigated (0.34+/-0.06). VCZ protein binding was concentration-independent and was on average 66.0+/-4.0%, allowing the prediction of free renal levels using pharmacokinetic parameters obtained from total plasma fitting. The results showed that VCZ free renal and free plasma levels are similar in healthy rats and in rats with disseminated candidiasis caused by C. albicans or C. krusei. Therefore, plasma free levels can be used to optimise dosing regimens for this drug.

Pharmacokinetic study of a carbamazepine nanoemulsion in beagle dogs

This work describes the pharmacokinetics of a novel carbamazepine nanoemulsion. The plasma concentration profiles were determined in beagle dogs after i.v. bolus administration of a 5 mg/kg carbamazepine nanoemulsion and compared to the corresponding carbamazepine/hydroxypropyl-beta-cyclodextrin complex solution. Both formulations showed similar pharmacokinetic profiles and could represent valuable formulations in case of emergencies, when a rapid action in the central nervous system is desirable.

Comparison of Fluconazole Renal Penetration Levels in Healthy and Candida albicans-Infected Wistar Rats

ABSTRACT The aims of this study were to evaluate free levels of fluconazole (FCZ) in the kidneys of healthy and Candida albicans-infected Wistar rats using microdialysis and to establish the relationship between free renal and total plasma levels under both conditions. Microdialysis recovery rates were determined in vitro by dialysis, and retrodialysis recovery rates were determined in vivo by retrodialysis. The recovery rate was around 50%, independent of the method, drug concentration, or condition (in vitro or in vivo) used. FCZ kidney penetration in healthy and infected rats was investigated after the administration of 10 mg/kg of body weight intravenously (i.v.) or 50 mg/kg orally (n = 6/group) and blood and microdialysate sample harvesting at predetermined time points up to 24 and 18 h, respectively. There were no statistical differences between the area under the free concentration-time curve (AUC0–∞) values in plasma and in tissue for either healthy or infected groups for the same dose regimen investigated. The antifungal tissue penetrations were similar for both doses and under all conditions investigated (ranging from 0.77 to 0.84). The unbound fraction of FCZ was concentration independent (86.0% ± 2.0%), allowing the prediction of free renal levels using pharmacokinetic parameters obtained from total plasma fitting. The results showed that free renal and free plasma levels are similar in healthy and systemically C. albicans-infected rats. Therefore, free plasma levels are a good surrogate to estimate free FCZ renal concentrations in systemic candidiasis and can be used to optimize dosing regimens for this drug.

Influence of Experimental Cryptococcal Meningitis in Wistar Rats on Voriconazole Brain Penetration Assessed by Microdialysis

ABSTRACT To make advances in the treatment of cryptococcal meningitis, it is crucial to know a given drugs free fraction that reaches the biophase. In the present study, we applied microdialysis (μD) as a tool to determine the free levels reached by voriconazole (VRC) in the brains of healthy and Cryptococcus neoformans-infected rats. The infection was induced by the intravenous (i.v.) administration of 1 × 105 CFU of yeast. The dose administered was 5 mg/kg (of body weight) of VRC, given i.v. Plasma and microdialysate samples were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and LC-UV methods. The free brain/free plasma ratio (fT) and population pharmacokinetic (popPK) analyses were performed to evaluate the impact of infection on PK parameters of the drug. The brain penetration ratio showed an increase on brain exposure in infected animals (fThealthy = 0.85 versus fTinfected = 1.86). The structural PK model with two compartments and Michaelis-Menten (MM) elimination describes the VRC concentration-time profile in plasma and tissue simultaneously. The covariate infection was included in volume of distribution in the peripheral compartment in healthy animals (V2) and maximum rate of metabolism (VM). The levels reached in infected tissues were higher than the values described for MIC of VRC for Cryptococccus neoformans (0.03 to 0.5 μg ml−1), indicating its great potential to treat meningitis associated with C. neoformans.

Does the Anesthetic Urethane Influence the Pharmacokinetics of Antifungal Drugs? A Population Pharmacokinetic Investigation in Rats

The aim of this paper was to analyze the impact of anesthesia induced by urethane on pharmacokinetics (PK) parameters of fluconazole (FCZ), mostly eliminated via renal excretion and voriconazole (VRC), eliminated mainly by hepatic metabolism. FCZ and VRC PK were investigated after administration of 10 mg/kg i.v. and 5 mg/kg i.v. doses to awake and urethane anesthetized Wistar rats (n = 6 per group), respectively. After dosing, blood samples were collected up to 18 h (FCZ) or 12 h (VRC) and the plasma data analysis was performed using the software MONOLIX v. 4.2.2. The population PK parameters and microconstants were determined by fitting plasma concentration-time profiles to two-compartment model for FCZ and three-compartment model for VRC. Fitting of FCZ plasma profiles after dosing to awake and anaesthetized animals resulted in a volume of distribution (V) of 9.3 and 8.1 L/kg, and k10 values of 0.12 and 0.14 h(-1) , respectively. VRC plasma profiles in awake and anaesthetized showed V 8.7 of and 7.6 L/kg, and k10 of 0.15 and 0.16 h(-1) , respectively. No statistical differences between plasma PK parameters and microconstants for the same drug in both animal conditions studied were observed (α = 0.05).

Validation of LC‐MS/MS method applied to evaluation of free tissue concentrations of vildagliptin in diabetic rats by microdialysis

A novel LC-MS/MS method was developed for the quantification of vildagliptin in an aqueous matrix. The method was successfully validated, meeting all the requisites of US Food and Drug Administration guide for a bioanalytical method. The developed method presented a limit of quantification of 10 ng/mL and the range of concentration achieved was 10-1875 ng/mL. The injection volume necessary was only 10 μL, and retention time was 4.60 min. The mobile phase employed was methanol-ammonium acetate 5 mm (95:5). The stability of the drug was evaluated in the different conditions through which the samples passed. A pharmacokinetic experiment was conducted with diabetic male Wistar rats, and the concentration of drug in liver was evaluated through a microdialysis technique. The perfusion fluid employed was ultrapure water. The dose administrated was 50 mg/kg and the method allowed the quantification of vildagliptin for more than three half lives, successfully characterizing the pharmacokinetic profile when the developed method was applied. This is the first report on the tissue pharmacokinetics of a DPP-4 inhibitor and could contribute to drug dosage optimization in the future.

Gemifloxacin mesylate (GFM): dissolution test based on in vivo data

Abstract Gemifloxacin mesylate (GFM) is a synthetic, broad-spectrum, fluoroquinolone antibacterial agent. It is different from other class members because it achieves adequate plasma concentrations to inhibit both topoisomerase IV and gyrase. The aim of this study was to develop and validate a dissolution test for GFM in coated tablets, using a simulated absorption profile based on in vivo data obtained from the literature. The fraction and percentage of the dose absorbed were calculated using model-dependent Loo-Riegelman approach for two compartments. The best in vitro dissolution profile was obtained using 900 mL of pH 6.0 phosphate buffer as a dissolution medium at 37 °C ± 0.5 °C and paddles at 50 rpm. The in vitro dissolution samples were analyzed using a liquid chromatography method, and the validation was performed according to USP 34 (2011). The method showed specificity, precision, accuracy, robustness and linearity. Under these conditions, a level-A in vitro–in vivo correlation was suggested (r = 0.9926). The prediction errors were calculated to determine the validity and accuracy of the suggested correlation. The dissolution test can be used to evaluate the dissolution profile of GFM-coated tablets and minimize the number of bioavailability studies as part of new formulation development.

Dissolution method for delapril and manidipine combination tablets based on an absorption profile of manidipine

The present study describes the development and validation of a dissolution method for delapril (DEL) and manidipine (MAN) combination tablets, using a simulated absorption profile based on in vivo data for MAN. The suitable in vitro dissolution profile for this formulation was obtained using 900 mL of citrate buffer pH 3.2 at 37 °C±0.5 °C as dissolution medium and USP apparatus 2 (paddle) at 75 rpm. All samples were analyzed by a liquid chromatography (LC) method. Under these conditions, a significant linear relationship between the absorbed (calculated by deconvolution approach) and dissolved fractions of MAN was obtained (R=0.997) and an in vivo-in vitro (IVIV) correlation for this particular formulation containing MAN can be established. Validation parameters for dissolution methodology such as the specificity, linearity, accuracy and precision were also evaluated according to the international guidelines, giving results within the acceptable range. Therefore, the proposed dissolution conditions can be applied for the simultaneous release analysis of DEL and MAN from the solid dosage form, contributing to the improvement of the quality control of pharmaceutics and minimizing the number of bioavailability studies.

Development and validation of a sensitive and selective LC—MS/MS method for the determination of an antimalarial drug candidate in rat plasma, and its application to a preclinical pharmacokinetic study

An accurate and reliable LC—MS/MS assay was firstly developed and validated for quantitative determination of a new antimalarial prototype drug, 3β-hydroxyurs-12-en-28-oic acid (LAFIS 01), in rat plasma. Dexamethasone was employed as internal standard. Simple protein precipitation by acetonitrile for the sample preparation was used. Effective separation was achieved with Phenomenex Luna C18 (50 × 2 mm, 5 μm) column. The mobile phase consisted of (A) water and (B) acetonitrile, both containing 0.1% acetic acid, delivered by gradient elution. The column temperature was maintained at 40 °C. The LAFIS 01 was monitored by electrospray ionization interface, operating in the negative mode (ESI−) in multiple reactions monitoring (MRM), checking the transitions 455 > 455 for LAFIS 01 and 451 > 361 for the IS. Once LAFIS 01 demonstrated low fragmentation by collision-induced dissociation (CID) nonpresenting abundant high-intensity fragments to meet the desired concentration levels quantification, only pseudomolecul...