HPLC method for assessment of in vitro and in vivo recovery of gatifloxacin using microdialysis

A simple and sensitive HPLC method was validated for assessment of in vitro and in vivo recovery of gatifloxacin using microdialysis. The validation parameters of linearity, precision, accuracy and limit of detection were studied as well as stability. Correlation coefficient (r2) obtained was > 0.999 for all calibration curves (20-600 ng.mL-1). Intra- and inter-day precision, expressed as the relative standard deviation (RSD) were less than 1.59 % and 1.33 %, respectively. Acceptable accuracy was achieved for all concentrations (99.17-101.35 %). The limit of quantification of the method was 20 ng.mL-1. The method showed the stability of gatifloxacin when submitted to different conditions. The validated method was applied to study calibration of microdialysis probes. The probe recovery was determined by no net flux experiment in vitro and in vivo. The in vitro and in vivo recovery for gatifloxacin was 30.9 ± 2.9 % and 28.9 ± 0.8 %, respectively. No differences were found between the two approaches. The HPLC method offers advantages because it has no extra sample handling steps; it is sensitive and can be used to determine free concentrations of gatifloxacin in tissues.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Characterizing the mechanism of quetiapine distribution in lipid-core nanocapsules pseudo-phases using a validated LC/UV method

Quetiapine is an atypical antipsychotic used to treat schizophrenia. However, despite great interest for its chronic therapeutic use, quetiapine has some important side effects such as weight gain induction. The development of a quetiapine nanocarrier can potentially target the drug into central nervous system, resulting in a reduction of systemic side effects and improved patient treatment. In the present work, a simple liquid chromatography/ultraviolet detection (LC/UV) analytical method was developed and validated for quantification of total quetiapine content in lipid core nanocapsules as well as for determination of incorporation efficiency. An algorithm proposed by Oliveira et al. (2012) was applied to characterize the distribution of quetiapine in the pseudo-phases of the nanocarrier, leading to a better understanding of the quetiapine nanoparticles produced. The analytical methodology developed was specific, linear in the range of 0.5 to 100 µg mL−1 (r2 > 0,99), and accurate and precise (R.S.D < ±5%). The absolute recovery of quetiapine from the nanoparticles was approximately 98% with an incorporation efficiency of approximately 96%. The results indicated that quetiapine was present in a type III distribution according to the algorithm, and was mainly located in the core of the nanoparticle because of its logD in the formulation pH (6.86 ± 0.4)

Analysis of in vivo absorption of didanosine tablets in male adult dogs by HPLC

AbstractDidanosine is an effective antiviral drug in untreated and antiretroviral therapy-experienced patients with Human Immunodeficiency Virus (HIV). An automated system using on-line solid extraction and High Performance Liquid Chromatography (HPLC) with ultraviolet (UV) detection was developed and validated for pharmacokinetic analysis of didanosine in dog plasma. Modifications were introduced on a previous methodology for simultaneous analysis of antiretroviral drugs in human plasma. Extraction was carried out on C18 cartridges, with high extraction yield as stationary phase, whereas mobile phase consisted of a mixture of 0.02 M potassium phosphate buffer, acetonitrile (KH2PO4: acetonitrile: 96:4, v/v) and 0.5% (w/v) of heptane sulphonic acid. The pH was adjusted to 6.5 with triethylamine. All samples and standard solutions were chromatographed at 28°C. For an isocratic run, the flux was 1.0mL/min, detection was at 250nm and injected volume was 20μL. The method was selective and linear for concentrations between 50 and 5000ng/mL. Drug stability data ranged from 96% to 98%, and limit of quantification was 25ng/mL. Extraction yield was up to 95%. Drug stability in dog plasma was kept frozen at −20°C for one month after three freeze–thaw cycles, and for 24h after processing in the auto sampler. Assay was successfully applied to measure didanosine concentrations in plasma dogs

Compartmental analysis of ranitidine doubled peak plasma profile after oral administration to healthy volunteers

O objetivo deste trabalho foi o duplo pico observado no perfil farmacocinético plasmático da ranitidina após administração oral a voluntários sadios através de análise compartimental. Uma dose simples de 300 mg de ranitidina foi administrada a dez voluntários sadios (5 homens e 5 mulheres). Amostras de sangue foram coletadas em diferentes tempos e analisadas por HPLC. Os perfis plasmáticos foram avaliados pela abordagem compartimental e nãocompartimental. Os parâmetros não compartimentais determinados foram k (0,0054 ± 0,001 min¹), t² (2,2 ± 0,4 h), Vd/F (265,3 ± 70,6 L), Cl/F (84,8 ± 24,3 L/h) e AUC (225916 ± 54099 ng*min/mL). A análise compartimental foi conduzida utilizando-se o modelo de dois compartimentos corporais com constantes de absorção de primeira ordem a partir de dois sítios de absorção diferentes. Os parâmetros determinados foram k21 (0,0149 ± 0,0133 min¹), k a1 (0,0117 ± 0,0073 min¹), k a02(0,1496 ± 0,1699 min¹), Vc (128 ± 75,2 L), a (0,0299 ± 0,0319 min¹), b (0,0074 ± 0,0014 min¹) e o tempo para o início da absorção no segundo sítio (126,7 ± 58,1 min). O modelo usado na análise compartimental foi adequado para descrever o duplo pico no perfil plasmático da ranitidina e para determinar os parâmetros farmacocinéticos.The aim of this study was to describe the double peak plasma pharmacokinetic profile of ranitidine after oral administration to healthy volunteers using non-compartmental and compartmental analysis. A single 300 mg dose of ranitidine was given to ten healthy volunteers (5 male and 5 female). Blood samples were drawn at different times and analyzed by HPLC. Plasma profiles were evaluated by non-compartmental and compartmental approaches. The non-compartmental parameters determined were k (0.0054 ± 0.0010 min-1), t1/2ss/F (265.3 ± 70.6 L), Cl/F (84.8 ± 24.3 L/h) and AUC (225916 ± 54099 ng*min/mL). The compartmental analysis was carried out using a two compartments body model, with first order absorption from two different sites. The parameters determined were k21 (0.0149 ± 0.0133 min-1), k a1(0.0117 ± 0.0073 min-1), k a2 (0.1496 ± 0.1699 min-1), Vc (128 ± 75.2 L), a (0.0299 ± 0.0319 min-1), b (0.0074 ± 0.0014 min-1) and time for the beginning of the absorption from the second site (126.7 ± 58.1 min). The model used in the compartmental analysis was adequate to describe the double peak of ranitidine plasma profile and to determine the pharmacokinetic parameters

Clinical and pharmacokinetic study of fractionated doses of oral etoposide in pediatric patients with advanced malignancies

The purpose of this phase I study was to evaluate the toxicity profile, dose-limiting toxicities (DLT), maximum tolerated dose (MTD), and plasma pharmacokinetics of oral etoposide, and to recommend a safe fractionated dose for phase II trials in pediatric patients with refractory solid tumors. Material/Methods: All patients had tumors no longer amenable to established forms of treatment. The initial dose of etoposide was 20 mg/m2 TID for 14 days every 21 days (dose-level I). Etoposide plasma pharmacokinetics were studied on day 1 of treatment and determined by HPLC. Results: Seventeen children were enrolled, 13 of whom were included in the pharmacokinetic study, for a total of 64 courses. Nine patients were included at dose-level I; grade 2–3 leucopenia was observed in 5. The dose was then raised to 25 mg/m2 (dose-level II) in another 8 patients; grade 3–4 leucopenia was observed in 4. This dose-level was therefore considered the MTD. The DLT was neutropenia. In patients at dose-level I and II the maximum plasma etoposide concentration was 2.97 and 8.59 μg/ml, respectively. Drug levels > 1 μg/ml were maintained for about 6.3 hours following drug administration at both dose-levels. Partial response was observed in 1 patient and 4 patients showed stable disease. Conclusions: Prolonged oral etoposide was well tolerated by our patients. Considering the MTD, and the fact that the patients included at dose-level I achieved an adequate (>1 μg/ml) plasma concentration of etoposide for a sufficient time, this dose level was recommended for phase II studies in pediatric malignancies. This work was performed at the Pediatric Oncology Service, Hospital de Clínicas de Porto Alegre; the Pediatric Hematology-Oncology Service, Hospital da Crianca Conceicao; and at the South American Office for Anticancer Drug Development (SOAD), Porto Alegre, Brazil

CHARACTERIZING THE MECHANISM OF QUETIAPINE DISTRIBUTION IN LIPID-CORE NANOCAPSULES PSEUDO-PHASES USING A VALIDATED LC/UV METHOD

Quetiapine is an atypical antipsychotic used to treat schizophrenia. However, despite great interest for its chronic therapeutic use, quetiapine has some important side effects such as weight gain induction. The development of a quetiapine nanocarrier can potentially target the drug into central nervous system, resulting in a reduction of systemic side effects and improved patient treatment. In the present work, a simple liquid chromatography/ultraviolet detection (LC/UV) analytical method was developed and validated for quantification of total quetiapine content in lipid core nanocapsules as well as for determination of incorporation efficiency. An algorithm proposed b