Bupivacaine in alginate and chitosan nanoparticles: an in vivo evaluation of efficacy, pharmacokinetics, and local toxicity

Objective

This study reports a preclinical evaluation of an alginate/chitosan nanoparticle formulation containing NovaBupi®, a racemic bupivacaine (BVC) containing 25% dextrobupivacaine and 75% levobupivacaine.

Methods

New Zealand White rabbits (n=6) received intraoral or intrathecal injections of BVC 0.5% or BVC 0.5%-loaded alginate–chitosan nanoparticles (BVC_ALG). BVC plasma levels and pharmacokinetic parameters were determined in blood samples of these rabbits. An infraorbital nerve blockade was performed in male Wistar rats (n=7) with the same formulations and the vehicle (NP_ALG). Histological evaluation of local toxicity after 6 hours and 24 hours of the treatments was performed in rats’ (n=6) oral tissues.

Results

No statistically significant difference was observed between plasma concentrations and pharmacokinetic parameters (p>0.05) after intraoral injections. However, after intrathecal injection BVC_ALG changed approximately three times the values of volume of distribution and area under the curve (AUC_0–t; p<0.05). The total analgesic effect of BVC after infraorbital nerve blockade was improved by 1.4-fold (p<0.001) with BVC_ALG. BVC and BVC_ALG did not induce significant local inflammatory reaction.

Conclusion

The encapsulation of BVC prolongs the local anesthetic effect after infraorbital nerve blockade and altered the pharmacokinetics after intrathecal injection.

Expression of Toll-like receptors in enterocromaffin-like cells and their function in histamine release

INTRODUCTION

Enterocromaffin-like cells (ECL) are specialized endocrine gastric cells able to release histamine, which in turn controls gastric acid production by parietal cells. Helicobacter pylori infection and other conditions signal in the gastrointestinal tract via Toll-like receptors (TLRs) and modify gastric acid production, but there is no evidence of expression and function of TLRs in ECL cells. In this work, we analyzed gene and protein expression of TLR-2, 4, 5, and 9, and other molecules involved in TLR signaling in ECL cells.

MATERIAL AND METHODS

ECL cells were isolated from Sprague-Dawley rats. The histamine-releasing ability of TLR ligands was also evaluated after culture of the ECL cells for a short time.

RESULTS

With ECL cells that expressed the TLR-2, TLR-4, TLR-5, and TLR-9 genes we were able to confirm protein expression for TLR-2, TLR-5, and TLR-9. Functionally, ECL cells were able to release histamine in response to TLR-2 stimulation by peptidoglycan (PGN), a TLR-2 ligand. After PGN stimulus, IRAK and p38 phosphorylation could be observed. SB 203580, a p38 inhibitor, reversed PGN-induced histamine release. Lipopolysaccharide (LPS), a TLR-4 ligand, was also able to induce histamine release in ECL cells, but by a mechanism independent of TLRs.

CONCLUSIONS

We have demonstrated for the first time that ECL cells express TLRs and respond to TLR-2 ligand by increasing histamine release. This response could be involved in host defense against gastrointestinal bacterial pathogens but could also contribute to control of gastric acid secretion in the absence of pathogens.

Determination of nimodipine in plasma by HPLC-MS/MS and pharmacokinetic application

To develop and validate a rapid, specific and highly sensitive method to quantify nimodipine in human plasma using dibucaine as the internal standard (IS). The analyte and IS were extracted from plasma samples by liquid-liquid extraction using hexane-ethyl acetate (1:1 v/v). The chromatographic separation was performed on a Varian® Polaris C18 analytical column (3 μm, 50 x 2.0 mm) and pre-column SecurityguardTM C18 (4.0 x 3.0 mm) with a mobile phase of Acetonitrile-Ammonium acetate 0.02 ml/L (80:20v/v). The method had a chromatographic run time of 4.5 min and linear calibration curve over the range of 0.1- 40 ng/mL (r > 0.9938). The limit of quantification was 100 pg/mL. Acceptable precision and accuracy were obtained for concentrations over the standard curve ranges. This validated method was successfully applied in determining the pharmacokinetic profile of nimodipine tablets of 30 mg administered to 24 healthy volunteers. The proposed method of analysis provided a sensitive and specific assay for nimodipine determination in human plasma. The time for the determination of one plasma sample was 4.5 min. This method is suitable for the analysis of nimodipine in human plasma samples collected for pharmacokinetic, bioavailability or bioequivalence studies in humans.

Avaliação do dano oxidativo ao DNA de células normais e neoplásicas da mucosa cólica de doentes com câncer colorretal

O estresse oxidativo ao DNA de células da mucosa cólica decorrente de radicais livres de oxigênio presentes na luz intestinal, induz mutações de genes relacionados ao controle do ciclo celular, representando um dos fenômenos iniciais da carcinogênese colorretal. A quantificação do dano oxidativo ao DNA em portadores de câncer colorretal foi pouco estudada até o momento. OBJETIVO: O objetivo do presente estudo foi mensurar os níveis de dano oxidativo ao DNA de células isoladas da mucosa cólica de doentes com câncer colorretal comparando o tecido normal e o neoplásico e correlacionando-os a variáveis anatomopatológicas. MÉTODO: Estudou-se 32 enfermos (19 mulheres) com média de idade de 60,6 ± 15,5 anos, portadores de adenocarcinoma colorretal operados consecutivamente, entre 2005 e 2006. A avaliação do dano oxidativo ao DNA foi realizada pela da versão alcalina do ensaio cometa (eletroforese e gel de célula única), a partir de fragmentos de tecido cólico normal e neoplásico obtidos imediatamente após a extirpação do espécime cirúrgico. Avaliou-se a extensão das rupturas das hélices do DNA com método de intensificação de imagem, em 200 células escolhidas aleatoriamente (100 de cada amostra de tecido) com o programa Komet 5.5. A mensuração da cauda obtida de cada célula (Tail Moment) representava, quantitativamente, a extensão do dano oxidativo ao DNA. A análise estatística das variáveis consideradas foi realizada pelos testes t de Student, qui-quadrado e Kruskal-Wallis, adotando-se nível de significância de 5% (p<0,05). RESULTADOS: Verificou-se em todos os doentes que as células obtidas do tecido neoplásico apresentavam maior intensidade de dano oxidativo ao DNA do que as células oriundas do tecido normal. As células isoladas da mucosa cólica neoplásica apresentavam, em média, extensão de ruptura das hélices do DNA (T.M. = 2,532 ± 0,945) significativamente maior quando comparadas às células isoladas do tecido normal (T.M. = 1,056 ± 0,460) (p=0,00001; I.C.95%: -1,7705 -1.1808). Verificou-se que os doentes pertencentes aos estádios mais precoces da classificação de Dukes e TNM apresentavam maiores níveis de dano oxidativo do que os pertencentes a estádios mais avançados (p=0,04 e p=0,001 respectivamente). CONCLUSÕES: As células obtidas do tecido normal de portadores de câncer colorretal apresentam sinais de danos oxidativos ao DNA celular, embora significativamente menores que as células neoplásicas.

Bioequivalence of two enteric coated formulations of pantoprazole in healthy volunteers under fasting and fed conditions

PURPOSE

To compare the bioavailability of two pantoprazole (CAS 102625-70-7) formulations (40 mg pantoprazole enteric coated tablets) under fasted and fed conditions as well as to evaluate the dissolution profile in biorelevant media.

METHODS

The subjects received either 40 mg of the reference or of test formulation in fasting (n = 28) and fed (n=70) condition. The studies were conducted according to a single dose and randomized crossover design. Blood samples were collected up to 12 h after drug administration in fasting condition and up to 48 h in fed condition. Plasma concentrations of pantoprazole were determined by LC-MS/MS. Pharmacokinetic parameters were calculated from the observed plasma concentration-time profiles. Bioequivalence between the formulations in fasting and fed condition was assessed considering 90% confidence intervals for the ratio of means for lnCmax and lnAUC(0-t) within 0.8-1.25. Dissolution profiles were evaluated in biorelevant media [Fasting State Simulating Intestinal Fluid (FaSSIF) and Fed State Simulating Intestinal Fluid (FeSSIF)]. The sameness of the dissolution curves was assessed by f2 values between 50 and 100.

RESULTS

Under fasting condition the 90% confidence interval for the ratio of means for the lnCmax, (0.94-1.03) and lnAUC(0-t) (0.89-0.99) was within the guideline range of bioequivalence (0.80-1.25). However, the data for lnCmax (0.51-0.76) and lnAUC(0-t) (0.68-0.90) under fed condition were not within the bioequivalence range. The postprandial study demonstrated a high intra-subject variability and in some subjects pantoprazole could not be detected for up to 24 h, although the dissolution profile of reference and test formulations presented a similar disposition in FaSSIF and FeSSIF as confirmed by the values of f2 higher than 50.

CONCLUSION

The results demonstrated that the test formulation was bioequivalent to the reference in fasting condition but not in postprandial state. The dissolution profile in FaSSIF indicates that this biorelevant medium was more adequate to discriminate the in vivo disposition of pantoprazole than FeSSIF. Furthermore, the fed condition study had shown a pronounced influence of food in the absorption of pantoprazole after single oral dose administration.