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.

Development of innovative oil-core self-organized nanovesicles prepared with chitosan and lecithin using a 2(3) full-factorial design.

The aim of this study was to develop innovative nanosystems with isopropyl myristate as the oil core of self-assembly nanovesicles constituted of chitosan and lecithin using a 2(3) factorial design. The factors analyzed were chitosan (X1, levels 4 and 8 mg/ml), oil (X2, levels 10 and 20 mg/ml) and lecithin (X3, levels 4 and 8 mg/ml). The responses evaluated were diameter, zeta potential, pH, viscosity, and backscattering analysis. The bioavailability was evaluated after oral administration of clozapine free and nanoencapsulated in rats. The diameter ranged from 0.348 to 1.5 µm for F2 (X1, 4; X2, 10; X3, 8 mg/ml) and F7 (X1, 8; X2, 20; X3, 4 mg/ml), respectively. Laser diffractometry analysis revealed only one diameter population for all batches. Zeta potential was positive, being influenced by X1 and X2/X3 association. Viscosity values were dependent on the X1 and X2 concentrations used. A structure proposed for the nanosystem consists of chitosan forming the hydrophilic shell layer that protects the core comprised of lecithin and the hydrophobic groups of oil. The AUC0-∞ was almost 3 times higher with the clozapine nanoencapsuted in relation to free drug. It was developed a new nanosystem which is able of improving the absorption of drugs.

Exploration of Brazilian biodiversity and selection of a new oleaginous yeast strain cultivated in raw glycerol.

The objective of this study was to use glycerol generated from the synthesis of biodiesel to study the oleaginous potential of wild yeasts. An initial selection was performed via a rapid and qualitative technique by staining with Sudan Black B. Initially 129 yeasts were present, from which 5 were selected and cultivated in liquid medium containing pure or raw glycerol. The yeast LEB-M3, isolated from the Pantanal, presented lipid content of 20.46% and 56.58% for cultivation in pure and raw glycerol, respectively. This strain was genotypically identified as Candida sp. The fatty acid profile showed predominance of oleic acid (C18:1), 57.35% for cultivation in pure glycerol, and in raw glycerol linoleic acid (C18:2) was predominant (46.0%). It was possible to select a yeast with high lipid concentrations 9.14 g/L and fatty acid profile similar to vegetable oils commonly used in the synthesis of biodiesel.

Comparison of fluconazole renal penetration levels in healthy and Candida albicans-infected Wistar rats.

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 (AUC(0-∞)) 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.

Isotretinoin-loaded nanocapsules: stability and cutaneous penetration by tape stripping in human and pig skin.

The cutaneous penetration of isotretinoin-loaded poly(epsilon-caprolactone) nanocapsules (GEL-NCISO) was compared to that of free isotretinoin (GEL-FREE) incorporated in hydrogels by tape stripping in excised human and pig skin. The physicochemical stability of isotretinoin-loaded nanocapsules and a nanoemulsion (used as a control) was evaluated using multiple light scattering, quantifying drug content and determining particle size, polydispersion index, zeta potential and pH for 60 days. A photostability study was also carried out. GEL-FREE and GEL-NCISO were applied to human and pig skin and penetration was assessed by tape stripping in Franz diffusion cells. The isotretinoin-loaded nanocapsules showed suitable physicochemical characteristics for topical administration, physical stability for 2 months at room temperature and under UVA radiation. In vitro tape stripping in human and pig skin showed that no isotretinoin reaches the receptor compartment for both formulations up to 8 h. Nanoencapsulation increased isotretinoin skin penetration for both skin stratum corneum. Pig skin was more permeable than human since higher isotretinoin concentrations were found at human upper skin layers for both formulations. Similar proportion of cutaneous penetration for human and pig skin were observed although different amounts of drug were detected in the stratum corneum of both skin specimens in vitro. A positive Pearson product moment correlation coefficient (0.79) between human and pig skin penetration in vitro was obtained, thus, pig skin can be considered suitable for predicting cutaneous penetration of isotretinoin in humans in vitro.

Pharmacokinetic/pharmacodynamic modelling of the bactericidal activity of free lung concentrations of levofloxacin and gatifloxacin against Streptococcus pneumoniae.

The aim of this work was to compare the pharmacological properties of levofloxacin and gatifloxacin against Streptococcus pneumoniae by pharmacokinetic/pharmacodynamic (PK/PD) modelling of the time-kill curves employing an E(max) model. An in vitro infection model was used to simulate free pulmonary fluctuating concentrations expected after multiple dosing regimens of both drugs in humans or constant multiples of the minimum inhibitory concentration. PK/PD parameters and PK/PD indices of the simulated dosing regimens were compared. The levofloxacin EC(50) (concentration producing 50% of the maximum effect) (mean ± standard deviation 3.57±2.16 mg/L) was higher than that for gatifloxacin (0.95±0.56 mg/L) when simulating multiple dosing regimens as well as constant concentrations (EC(50,levofloxacin)=2.75±0.45 mg/L; EC(50,gatifloxacin)=1.03±0.52 mg/L). The maximum killing rate constant (k(max)) was not statistically different for both drugs independent of fluctuating (k(max,levofloxacin)=0.40±0.19 h(-1); k(max,gatifloxacin)=0.48±0.15 h(-1)) or constant concentrations (k(max,levofloxacin)=0.34±0.06 h(-1); k(max,gatifloxacin)=0.39±0.23 h(-1)). The PK/PD model was able to describe the effect of levofloxacin and gatifloxacin against S. pneumoniae in vitro for all the simulations investigated. Gatifloxacin was more potent than levofloxacin, but both presented equivalent efficacy. The model can be used for simulating alternative regimens and optimising therapy to treat streptococcal infextions.

Acute hemorrhagic edema of infancy: a case report.

BACKGROUND: Acute hemorrhagic edema of infancy (AHEI), or Seidlmayer's disease, is a type of leukocytoclastic vasculitis proper of infants and children. It is characterized by a local increase in temperature, erythematous edema and purpuric lesions involving mainly the face and extremities. There usually is no visceral involvement. The disease is self-limited, bearing a benign clinical course. Infection, drugs and immunization have been considered as precipitating factors. The main differential diagnosis is Henoch-Schönlein purpura (HSP). METHODS: We describe a classic example of acute hemorrhagic edema of infancy, and comment on the clinical features, pathology, immunopathology and proposed therapy. We characterize the differences between AHEI and HSP. RESULTS: A course of corticosteroids was given to avoid quick progression of disease. CONCLUSION: Acute hemorrhagic edema of infancy is a rare disease, and the most striking classic feature of the disease is the contrast between the acuteness of the cutaneous lesions and the good general condition of the patient. Considering its clinical features, pathology and immunopathology, AHEI can be justifiably characterized as a unique disorder, distinct from HSP.