RESUMO
The aim of this study was to evaluate the in vitro cytotoxicity and the in vivo analgesic effect and local toxicity of the local anesthetic butamben (BTB) encapsulated in conventional or elastic liposomes incorporated in gel formulations. The results showed that both gel formulations of liposomal BTB reduced the cytotoxicity (p < 0.001; one-way ANOVA/Tukey's test) and increased the topical analgesic effect (p < 0.05; one-way ANOVA/Tukey's test) of butamben, compared to plain BTB gel. The gel formulations presented good rheological properties, and stability assays detected no differences in physicochemical stability up to 30 d after preparation. Moreover, histological assessment revealed no morphological changes in rat skin after application of any of the gel formulations tested.
Assuntos
Anestesia Local/efeitos adversos , Benzocaína/análogos & derivados , Modelos Animais de Doenças , Géis/toxicidade , Lipossomos/toxicidade , Células 3T3 , Administração Tópica , Animais , Benzocaína/administração & dosagem , Benzocaína/química , Benzocaína/toxicidade , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Géis/administração & dosagem , Géis/química , Injeções Intraperitoneais , Lipossomos/administração & dosagem , Lipossomos/química , Camundongos , Camundongos Endogâmicos BALB C , Ratos , Ratos WistarRESUMO
Local anesthetics are able to induce pain relief by binding to the sodium channel of excitable membranes, blocking the influx of sodium ions and the propagation of the nervous impulse. Benzocaine (BZC) is a local anesthetic whose low water-solubility limits its application to topical formulations. The present work focuses on the characterization of inclusion complexes of BZC in beta-cyclodextrin (beta-CD). Differential scanning calorimetry and electron microscopy gave evidences of the formation and the morphology of the complex. Fluorescence spectroscopy showed a BZC/beta-CD 1:1 stoichiometry. Phase-solubility diagrams allowed the determination of the association constants between BZC and beta-CD (549 M(-1)) and revealed that a three-fold increase in BZC solubility can be reached upon complexation with beta-CD. The details of BZC/beta-CD molecular interaction were analyzed by 1H 2D NMR allowing the proposition of an inclusion model for BZC into beta-CD where the aromatic ring of the anesthetic is located near the head of the beta-CD cavity. Moreover, in preliminary toxicity studies, the complex seems to be less toxic than BZC alone, since it induced a decrease in the in vitro oxidation of human hemoglobin. These results suggest that the BZC/beta-CD complex represents an effective novel formulation to enhance BZC solubility in water, turning it promising for use outside its traditional application, i.e., in infiltrative anesthesia.
Assuntos
Anestésicos Locais/química , Benzocaína/química , Benzocaína/toxicidade , beta-Ciclodextrinas/química , Anestésicos Locais/toxicidade , Disponibilidade Biológica , Varredura Diferencial de Calorimetria , Fenômenos Químicos , Físico-Química , Estabilidade de Medicamentos , Humanos , Técnicas In Vitro , Espectroscopia de Ressonância Magnética , Metemoglobina/química , Microscopia Eletrônica de Varredura , Modelos Moleculares , Tamanho da Partícula , Solubilidade , Espectrometria de Fluorescência , beta-Ciclodextrinas/toxicidadeRESUMO
Fish blood erythrocytes are frequently used as sentinels in biomonitoring studies. Usually, fish blood is collected by painful cardiac or caudal vein punctures. Previous anesthesia could decrease animal suffering but it is not known at present whether anesthesia can cause confounding effects. Therefore, using the alkaline single cell gel (SCG)/comet assay with blood erythrocytes of the cichlid fish Nile tilapia, we tested for a possible modulation of induced DNA damage (methyl methanesulfonate; MMS) by the anesthetic benzocaine administered by bath exposure (80mg/l for approximately 10min). Furthermore, benzocaine (80-600mg/l) was tested for its genotoxic potential on fish erythrocytes in vitro and for potential interactions with two known genotoxins (MMS and hydrogen peroxide). Our results did neither indicate a significant increase in the amount of DNA damage (even after a 48h follow-up), nor indicated interactions with MMS-induced DNA damage when fish were exposed to benzocaine in vivo. There was also no increase in DNA damage after in vitro exposure of fish erythrocytes to benzocaine. Clear concentration-related effects were observed for the two genotoxins in vitro, which were not significantly altered by the presence of benzocaine. These results suggest that anesthesia of fish does not confound comet assay results and the use of blood samples from anesthetized fish can be recommended with regard to animal welfare.