DoE development of ionic gradient liposomes: A successful approach to improve encapsulation, prolong anesthesia and decrease the toxicity of etidocaine.

Etidocaine (EDC) is a long-acting local anesthetic of the aminoamide family whose use was discontinued in 2008 for alleged toxicity issues. Ionic gradient liposomes (IGL) are nanostructured carriers for which an inner/outer gradient of ions increases drug upload. This work describes IGLEDC, a formulation optimized by Design of Experiments, composed of hydrogenated soy phosphatidylcholine:cholesterol:EDC, and characterized by DLS, NTA, TEM/Cryo-TEM, DSC and 1H NMR. The optimized IGL showed significant encapsulation efficiency (41 %), good shelf stability (180 days) and evidence of EDC interaction with the lipid bilayer (as seen by DSC and 1H NMR results) that confirms its membrane permeation. In vitro (release kinetics and cytotoxicity) tests showed that the encapsulation of EDC into the IGL promoted sustained release for 24 h and decreased by 50 % the intrinsic toxicity of EDC to Schwann cells. In vivo IGLEDC decreased the toxicity of EDC to Caenorhabditis elegans by 25 % and extended its anesthetic effect by one hour, after infiltrative administration, at clinically used (0.5 %) concentration, in rats. Thus, this novel drug delivery system is a promise for the possible reintroduction of EDC in clinics, aiming at the control of operative and postoperative pain.

Sustained Release from Ionic-Gradient Liposomes Significantly Decreases ETIDOCAINE Cytotoxicity.

PURPOSE: Etidocaine (EDC) is a long lasting local anesthetic, which alleged toxicity has restricted its clinical use. Liposomes can prolong the analgesia time and reduce the toxicity of local anesthetics. Ionic gradient liposomes (IGL) have been proposed to increase the upload and prolong the drug release, from liposomes. METHODS: First, a HPLC method for EDC quantification was validated. Then, large unilamellar vesicles composed of hydrogenated soy phosphatidylcholine:cholesterol with 250 mM (NH4)2SO4 - inside gradient - were prepared for the encapsulation of 0.5% EDC. Dynamic light scattering, nanotracking analysis, transmission electron microscopy and electron paramagnetic resonance were used to characterize: nanoparticles size, polydispersity, zeta potential, concentration, morphology and membrane fluidity. Release kinetics and in vitro cytotoxicity tests were also performed. RESULTS: IGLEDC showed average diameters of 172.3 ± 2.6 nm, low PDI (0.12 ± 0.01), mean particle concentration of 6.3 ± 0.5 × 1012/mL and negative zeta values (-10.2 ± 0.4 mV); parameters that remain stable during storage at 4°C. The formulation, with 40% encapsulation efficiency, induced the sustained release of EDC (ca. 24 h), while reducing its toxicity to human fibroblasts. CONCLUSION: A novel formulation is proposed for etidocaine that promotes sustained release and reduces its cytotoxicity. IGLEDC can come to be a tool to reintroduce etidocaine in clinical use.

Preferential location of lidocaine and etidocaine in lecithin bilayers as determined by EPR, fluorescence and 2H NMR.

We have examined the effect of the uncharged species of lidocaine (LDC) and etidocaine (EDC) on the acyl chain moiety of egg phosphatidylcholine liposomes. Changes in membrane organization caused by both anesthetics were detected through the use of EPR spin labels (5, 7 and 12 doxyl stearic acid methyl ester) or fluorescence probes (4, 6, 10, 16 pyrene-fatty acids). The disturbance caused by the LA was greater when the probes were inserted in more external positions of the acyl chain and decreased towards the hydrophobic core of the membrane. The results indicate a preferential insertion of LDC at the polar interface of the bilayer and in the first half of the acyl chain, for EDC. Additionally, (2)H NMR spectra of multilamellar liposomes composed by acyl chain-perdeutero DMPC and EPC (1:4 mol%) allowed the determination of the segmental order (S(mol)) and dynamics (T(1)) of the acyl chain region. In accordance to the fluorescence and EPR results, changes in molecular orientation and dynamics are more prominent if the LA preferential location is more superficial, as for LDC while EDC seems to organize the acyl chain region between carbons 2-8, which is indicative of its positioning. We propose that the preferential location of LDC and EDC inside the bilayers creates a "transient site", which is related to the anesthetic potency since it could modulate the access of these molecules to their binding site(s) in the voltage-gated sodium channel.

Uso de anestésicos de longa ação em exodontias de terceiros molares / Use of long-acting local anaesthetics in third molar surgery

Este trabalho consiste numa revista de literatura que tem o propósito de familiarizar o Cirurgião Dentista sobre as soluções anestésicas de longa ação mais utilizados para as exodontias de terceiros molares impactados, além de compará-las com os anestésicos de longa ação normal. Os anestésicos de longa ação mostraram-se mais eficazes em relação ao controle da dor pós-operatória, apresentando, contudo, indicações e contra-indicações relativas que devem ser identificadas

Spectrophotometric determination of etidocaine in pharmaceutical (dental) formulation.

A spectrophotometric method was developed for the determination of etidocaine hydrochloride (EH) in injectable pharmaceutical preparation. The proposal of this work was to develop a rapid, simple, inexpensive, precise and accurate visible spectrophotometric method. The method is based on the formation of the ion-pair complex by the EH reaction with bromocresol green in the pH 4.6 which after chloroform extraction gives a yellow color that in basic medium change to blue color and exhibits a maximum absorbance at 625 nm. The calibration graph was linear over the range 2.0-6.0 microg ml(-1) EH calculated on the final yellow solution. The R.S.D. of the slope of the four lines was 0.73%. This method can be applied to injectable pharmaceutical preparation dosage studied.

Vasospasm and platelet deposition in human arteries: effects of topical methylene blue.

Vasodilation of small blood vessels is controlled in part by the endothelium-derived relaxing factor (EDRF), which also inhibits platelet adhesion. Methylene blue (MB), which is occasionally applied directly to blood vessels during microsurgery to provide orientation and prevent torsion, is an irreversible inhibitor of the effects of endothelium-derived relaxing factor and may thereby augment both vasospasm and platelet responses. We have investigated the effects of the extravascular adventitial application of methylene blue on platelet deposition to human placental arteries (HPA) in the presence and absence of surgically induced vasospasm. A trend toward increased platelet deposition to human placental arteries was seen in each group but did not reach significance. The degree of platelet deposition to control human placental arteries suggests that the effects of methylene blue on platelet deposition may be dwarfed by the effects of surgical trauma and ischemia.

Estudio comparativo de la acción anestésica tópica de Bupivacaína, Etidocaína y Tetracaína / Comparative study of the topical anesthetic action of Bupivacaine, Etidocaine and Tetracaine

Los anestésicos locales Bupivacaína y Etidocaína, aunque poseen una gran actividad y prolongada duración de su efecto, no tienen aplicación clínica como anestésicos de uso tópico. En esta investigación se estudia comparativamente con Tetracaína, la capacidad de estas sustancias de bloquear los impulsos sensitivos que se generan en la superficie corneal. Se utilizó el test de inhibición de reflejo corneal en el conejo, método que permite determinar tanto la duración como la intensidad del efecto anestésico tópico. Los resultados confirmaron observaciones previas y mostraron que Bupivacaína y Etidocaína bloquean la vía aferente de este reflejo con concentraciones milimolares y su actividad fue semejante a la de Tetracaína. La duración del efecto máximo (anestesia completa) varió entre 22 y 24 minutos, mientras que la depresión parcial del reflejo corneal se prolongó 80 a 100. Estos resultados sugieren que Bupivacaína y Etidocaína ejercen una potente acción anestésica sobre las superficies mucosas y por consiguiente, es necesario su estudio clínico en la mucosa bucal

Determinacao de lidocaina, prilocaina e etidocaina em amostras de sangue por cromatografia em fase gasosa. / Determination of lidocaine, prilocaine and etidocaine in blood by gas chromatography

E descrito um metodo de determinacao de lidocaina, prilocaina e etidocaina em amostras de sangue. Esses farmacos sao extraidos do material biologico, em meio alcalino, com diclorometano e a seguir determinados quantitativamente por cromatografia em fase gasosa. Este metodo permite a determinacao destes anestesicos locais, individualmente ou em associacao, quando presentes no sangue de pacientes que se submetem a uma anestesia regional