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.

Are There Differences in Fracture Patterns in Mandibular Ramus Sagittal Osteotomies Between Hunsuck/Epker, Wolford, and Posnick Modifications?

PURPOSE: Despite decades of study, the best technique for mandibular ramus sagittal osteotomy has not been definitively determined. The purpose of the present study was to compare fracture patterns, inferior alveolar nerve (IAN) visualization, and torque required for mandibular sagittal splitting using the Hunsuck/Epker, Wolford, and Posnick techniques. METHODS: This was a laboratory (ex vivo), randomized, a single-blind study performed to evaluate sagittal split osteotomies in porcine mandibles using a specifically designed test system. The study's predictor variable was the osteotomy technique, which was divided into 3 groups: Group Hunsuck/Epker (GHE), group Wolford (GW), and group Posnick (GP). The outcome variables were lingual fracture pattern, torque in newtons (N) required to separate the mandible, and IAN visualization. The covariates were mandibular radiodensity and time between dejection and the experiment. The Kolmogorov-Smirnov normality statistics and analysis of variance with Tukey post test statistics were performed. P value <.05 was considered statistically significant. RESULTS: The sample was composed of 120 equally divided porcine hemimandibles in each group. The torque forces were significantly lower (P < .001) when using the Posnick technique (2.07 ± 0.22 N) than when using the Hunsuck/Epker technique (4.45 ± 0.32 N) and Wolford (3.00 ± 0.21 N). GW (93.3%) and GHE (56.7%) showed a higher prevalence of lingual fracture in the posterior region of the mandibular canal (P < .001), while the GP (90%) had a higher frequency of lingual fracture pattern on the mylohyoid sulcus (P < .001). In more than 90% (P < .001) of the mandibles in GW and GHE, the IAN visualization was higher than 50%. In the GP, 90% (P < .001) of patients had IAN visualization of less than 50%. CONCLUSIONS: The Posnick technique required less torque to perform the sagittal osteotomy in a pig mandible and had good predictability (90%) for the less preferred lingual fracture pattern and minimal visualization of the nerve. The Wolford technique provided the best predictability (93%) for the preferred lingual fracture pattern and the best nerve visualization. Caution must be exercised when extrapolating the results from animal models to human applications.

Silk Fibroin/Poly(vinyl Alcohol) Microneedles as Carriers for the Delivery of Singlet Oxygen Photosensitizers.

Photodynamic therapy (PDT) is a medical treatment in which a combination of a photosensitizing drug and visible light produces highly cytotoxic reactive oxygen species (ROS) that leads to cell death. One of the main drawbacks of PDT for topical treatments is the limited skin penetration of some photosensitizers commonly used in this therapy. In this study, we propose the use of polymeric microneedles (MNs) prepared from silk fibroin and poly(vinyl alcohol) (PVA) to increase the penetration efficiency of porphyrin as possible applications in photodynamic therapy. The microneedle arrays were fabricated from mixtures in different proportions (1:0, 7:3, 1:1, 3:7, and 0:1) of silk fibroin and PVA solutions (7%); the polymer solutions were cast in polydimethylsiloxane (PDMS) molds and dried overnight. Patches containing grids of 10 × 10 microneedles with a square-based pyramidal shape were successfully produced through this approach. The polymer microneedle arrays showed good mechanical strength under compression force and sufficient insertion depth in both Parafilm M and excised porcine skin at different application forces (5, 20, 30, and 40 N) using a commercial applicator. We observe an increase in the cumulative permeation of 5-[4-(2-carboxyethanoyl) aminophenyl]-10,15,20-tris-(4-sulphonatophenyl) porphyrin trisodium through porcine skin treated with the polymer microneedles after 24 h. MNs may be a promising carrier for the transdermal delivery of photosensitizers for PDT, improving the permeation of photosensitizer molecules through the skin, thus improving the efficiency of this therapy for topical applications.

Comparative analysis of two laser wavelengths in the stimulation of acupuncture points for analgesic effects in an animal model.

This study compares the effectiveness of two laser wavelengths for stimulating acupoints in an experimental model of acute postoperative pain. Forty-five Wistar rats were randomly assigned to receive treatment on their left hind paw, contralateral to a surgical procedure. Laser treatments were performed with Green Laser-GL (532 nm, 70 mW and 7 J/cm2 of energy), Red Laser-RL (660 nm, 100 mW and 7 J/cm2 of energy), or with Laser Off-LO. After each application, the animals were evaluated with a Von Frey analgesiometer to check for painful sensitivity on their right (with surgery) and left (without surgery) hind paws. Neuropeptides and cytokine levels in the incision site tissue of the right paw were measured by ELISA after 1, 6 and 24 hours. It was possible to observe that, in this pain model, both lasers promoted analgesia and that the GL altered the levels of TNF-α and IL-1ß.

Ropivacaine-Loaded Poloxamer Binary Hydrogels for Prolonged Regional Anesthesia: Structural Aspects, Biocompatibility, and Pharmacological Evaluation.

This study reports the development of thermosensitive hydrogels for delivering ropivacaine (RVC), a wide clinically used local anesthetic. For this purpose, poloxamer- (PL-) based hydrogels were synthesized for evaluating the influence of polymer concentration, hydrophilic-lipophilic balances, and binary system formation on biopharmaceutical properties and pharmacological performance. Transition temperatures were shifted, and rheological analysis revealed a viscoelastic behavior with enhanced elastic/viscous modulus relationship (G'/G " = 1.8 to 22 times), according to hydrogel composition and RVC incorporation. The RVC release from PL407 and PL407/338 systems followed the Higuchi model (R 2 = 0.923-0.989), indicating the drug diffusion from hydrogels to the medium. RVC-PL hydrogels were potentially biocompatible evoking low cytotoxic effects (in fibroblasts and Schwann cells) and mild/moderate inflammation signs on sciatic nerve nearby histological evaluation. In vivo pharmacological assays demonstrated that PL407 and PL407/338 evoked differential analgesic effects, by prolonging the sensory blockade duration up to ~340 and 250 min., respectively. All those results highlighted PL407 and PL407/338 as promising new strategies for sustaining analgesic effects during the postoperative period.

Evaluation of Budesonide-Hydroxypropyl-ß-Cyclodextrin Inclusion Complex in Thermoreversible Gels for Ulcerative Colitis.

BACKGROUND: New formulations for topical treatment of ulcerative colitis with budesonide inclusion complex (BUDHP-ß-CD) and poloxamers (PL) were developed for future clinical use. AIMS: This study evaluated the efficacy of such novel formulations in a rat model of colitis. METHODS: The PL-BUDHP-ß-CD systems were prepared by direct dispersion of the complex (BUD concentration 0.5 mg mL-1) in solutions with PL407 or PL403. Male Wistar rats underwent TNBS-induced colitis and were treated for 5 days by a rectal route, as follows: BUD 1: BUDHP-ß-CD + PL407 (18%); BUD 2: BUDHP-ß-CD + PL407 (20%); BUD 3: BUDHP-ß-CD + PL407 (18%) + PL403 (2%); BUD 4: plain BUD; BUD 5: BUDHP-ß-CD; C1: HP-ß-CD + PL407 (18%); C2: HP-ß-CD + PL407 (20%); C3: HP-ß-CD + PL407 (18%) + PL403 (2%); C4: saline. A negative control group without colitis was also used. Colitis was assessed via myeloperoxidase (MPO) activity, and macroscopic and microscopic damage score in colon tissues. Protein levels of TNF-α, IL-1ß, IL-10 and endogenous glucocorticoids were obtained using ELISA. RESULTS: BUDHP-ß-CD poloxamer formulations had similar MPO activity when compared with the negative control group. All formulations presented lower MPO activity than BUDHP-ß-CD and plain BUD (p < 0.001). BUD 2 produced lower microscopic score values than plain BUD and BUDHP-ß-CD (p < 0.01). All formulations with BUDHP-ß-CD poloxamers reduced TNF-α levels (p < 0.05). CONCLUSION: Novel budesonide inclusion complex formulations improved microscopic damage and reduced colonic MPO activity and TNF-α levels.

Physico-Chemical Characterization and Biopharmaceutical Evaluation of Lipid-Poloxamer-Based Organogels for Curcumin Skin Delivery.

Organogels (ORGs) are semi-solid materials, in which an organic phase is immobilized by a three-dimensional network composed of self-organized system, forming the aqueous phase. In this context, lipid-Pluronics (PLs) ORGs form a two-phase system which can be effectively used as skin delivery systems, favoring their permeation across the skin. In this study, we presented the development of ORG skin drug-delivery systems for curcumin (CUR), a liposoluble phenolic pigment extracted from the turmeric rhizome. In special, we designed the formulation compositions in order to carry high amounts of CUR soluble in oleic acid (OA), as organic phase, entrapped into an aqueous phase composed of micellar PL-based hydrogels by associating two polymers with different hydrophilic-lipophilic balances, Pluronic F-127 (PL F-127), and Pluronic L-81 (PL L-81), to enhance the permeation across the skin. Results revealed that the incorporation of PL L-81 favored the CUR incorporation into micelle-micelle interface. CUR insertion into OA-PL F-127/L-81 reduced both G'/G" relationship (∼16 x) and viscosity values (η* ∼ 54 mPa.s, at 32.5°C), disturbing the ORG network structural organization. In vitro permeation assays through Strat-M® skin-model membranes showed that higher CUR-permeated amounts were obtained for OA-PL F-127/L-81 (4.83 µg.cm-2) compared to OA-PL F-127 (3.51 µg.cm-2) and OA (2.25 µg.cm-2) or hydrogels (∼1.2 µg.cm-2, p < 0.001). Additionally, ORG formulations presented low cytotoxic effects and evoked pronounced antileishmanial activity (IC50 < 1.25 µg.ml-1), suggesting their potential use as skin delivery systems against Leishmania amazonensis. Results from this study pointed out OA-PL-based ORGs as promising new formulations for possible CUR topical administration.

Synthesis and characterization of nanostructured lipid-poloxamer organogels for enhanced skin local anesthesia.

The aim of this study was to synthesize a novel drug delivery system using organogels (ORGs) and characterize its physicochemical properties, in vitro and ex vivo permeation abilities, cytotoxicity and in vivo local anesthetic effects. The ORG formulations contained a mixture of oleic acid-lanolin (OA-LAN), poloxamer (PL407), and the commonly used local anesthetic lidocaine (LDC). The main focus was to evaluate the impact of LAN and PL407 concentrations on the ORG structural features and their biopharmaceutical performance. Results revealed that LDC, OA, and LAN incorporation separately shifted the systems transitions phase temperatures and modified the elastic/viscous moduli relationships (G'/G″ = ~15×). Additionally, the formulation with the highest concentrations of LAN and PL407 reduced the LDC flux from ~17 to 12 µg·cm-2·h-1 and the permeability coefficients from 1.2 to 0.62 cm·h-1 through ex vivo skin. In vivo pharmacological evaluation showed that the ORG-based drug delivery system presented low cytotoxicity, increased and prolonged the local anesthetic effects compared to commercial alternatives. The data from this study indicate that ORG represent a promising new approach to effectively enhance the topical administration of local anesthetics.

Preclinical Evaluation of Ropivacaine in 2 Liposomal Modified Systems.

BACKGROUND: Our research group has recently developed liposomes with ionic gradient and in a combined manner as donor and acceptor vesicles containing ropivacaine (RVC; at 2% or 0.75%). Looking for applications of such novel formulations for postoperative pain control, we evaluated the duration of anesthesia, pharmacokinetics, and tissue reaction evoked by these new RVC formulations. METHODS: The formulations used in this study were large multivesicular vesicle (LMVV) containing sodium acetate buffer at pH 5.5 or in a combined manner with LMVV as donor and large unilamellar vesicles (LUVs) as acceptor vesicles with an external pH of 7.4. Wistar rats were divided into 6 groups (n = 6) and received sciatic nerve block (0.4 mL) with 6 formulations of RVC (LMVVRVC0.75%, LMVV/LUVRVC0.75%, LMVVRVC2%, LMVV/LUVRVC2%, RVC 0.75%, and RVC 2%). To verify the anesthetic effect, the animals were submitted to the pain pressure test and the motor block was also monitored. Histopathology of the tissues surrounding the sciatic nerve region was also assessed 2 and 7 days after treatment. Rats (n = 6) were submitted to a hind paw incision, and mechanical hypersensitivity was measured via the withdrawal response using von Frey filaments after injection of the 6 formulations. Finally, New Zealand white rabbits (n = 6) received sciatic nerve block (3 mL) with 1 of the 6 formulations of RVC. Blood samples were collected predose (0 minutes) and at 15, 30, 45, 60, 90, 120, 180, 240, 300, 360, 420, 480, and 540 minutes after injection. RVC plasma levels were determined using a triple-stage quadrupole mass spectrometer. RESULTS: Duration and intensity of the sensory block were longer with all liposomal formulations, when compared to the plain RVC solution (P < .05). Histopathological evaluation showed greater toxicity for the positive control (lidocaine 10%), when compared to all formulations (P < .05). After the hind paw incision, all animals presented postincisional hypersensitivity and liposomal formulations showed longer analgesia (P < .05). LMVVRVC0.75% presented higher time to reach maximum concentration and mean residence time than the remaining formulations with RVC 0.75% (P < .05), so LMVV was able to reduce systemic exposure of RVC due to slow release from this liposomal system. CONCLUSIONS: All new liposomal formulations containing 0.75% RVC were able to change the pharmacokinetics and enhance anesthesia duration due to slow release of RVC from liposomes without inducing significant toxic effects to local tissues.

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 (BVCALG). 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 (NPALG). 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 BVCALG changed approximately three times the values of volume of distribution and area under the curve (AUC0-t; p<0.05). The total analgesic effect of BVC after infraorbital nerve blockade was improved by 1.4-fold (p<0.001) with BVCALG. BVC and BVCALG 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.

Current Challenges and Future of Lipid nanoparticles formulations for topical drug application to oral mucosa, skin, and eye.

BACKGROUND: Topical drug administration offers an attractive route with minimal invasiveness. It also avoids limitations of intravenous administration such as the first pass metabolism and presystemic elimination within the gastrointestinal tract. Furthermore, topical drug administration is safe, have few side effects, is easy to apply, and offers a fast onset of action. However, the development of effective topical formulations still represents a challenge for the desired effect to be reached, locally or systemically. Solid lipid nanoparticles and nanostructured lipid carriers are particular candidates to overcome the problem of topical drug administration. The nanometric particle size of lipid nanoparticles favors the physical adhesion to the skin or mucosal, what can also be attained with the formation of hybrid (nanoparticles/polymer) systems. METHODS: In this review, we discuss the major challenges for lipid nanoparticles formulations for topical application to oral mucosa, skin, and eye, highlighting the strategies to improve the performance of lipid nanoparticles for topical applications. Next, we critically analyzed the in vitro and in vivo approaches used to evaluate lipid nanoparticles performance and toxicity. CONCLUSION: We addressed some major drawbacks related to lipid nanoparticle topical formulations and concluded the key points that have to be overcome to help them to reach the market in topical formulations to oral mucosa, skin and eye.

Pharmacokinetics and Pharmacodynamics Evaluation of Tramadol in Thermoreversible Gels.

We evaluated pharmacokinetics (PK) and pharmacodynamics (PD) induced by new formulations of tramadol (TR) in thermoreversible gels. The poloxamer- (PL-) tramadol systems were prepared by direct dispersion of the drug in solutions with PL 407 and PL 188. The evaluated formulations were as follows: F1: TR 2% in aqueous solution and F2: PL 407 (20%) + PL 188 (10%) + TR 2%; F3: PL 407 (25%) + PL 188 (5%) + TR 2%; F4: PL 407 (20%) + TR 2%. New Zealand White rabbits were divided into four groups (n = 6) and treated by subcutaneous route with F1, F2, F3, or F4 (10 µg·kg-1). PK evaluation used TR and M1 plasma levels. PD evaluation was performed with the measurement of both pupils' diameters. F2 showed higher TR plasma concentration after 180 minutes and presented lower M1 concentrations at almost all evaluated periods. Areas under the curve (ASC0-480 and ASC0-∞ ) and clearance of F2 presented differences compared to F1. F2 presented significant correlation (Pearson correlation) between the enhancement of TR and M1 concentrations and the decrease of pupil size (miosis). Thus, F2 was effective in altering pharmacokinetics and pharmacodynamics effects of TR.

Liposomal butamben gel formulations: toxicity assays and topical anesthesia in an animal model.

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.

Budesonide-hydroxypropyl-ß-cyclodextrin inclusion complex in binary poloxamer 407/403 system for ulcerative colitis treatment: A physico-chemical study from micelles to hydrogels.

Budesonide (BUD) is a glucocorticoid widely used for the treatment of ulcerative colitis. In this work, we propose the study of the system BUD-HP-ß-CD inclusion complex incorporated into PL 407 and PL407-PL403 thermoreversible hydrogels, considering physico-chemical and pharmaceutical aspects. Complexation between BUD and HP-ß-CD was confirmed by phase solubility studies (1:1 stoichiometry, Kc=8662.8 M(-1)), DSC, FTIR and microscopy analyzes. BUD solubility in simulated upper and lower colon fluids was improved in a dependence of HP-ß-CD and PL 407 or PL407-PL403 association. Micellar hydrodynamic diameter studies showed the interaction between HP-ß-CD and PL blocks, as well as the reorganization of the micellar system in the presence of BUD and its inclusion complex. Micellization temperature (Tm) was not shifted, but sol-gel phase transition studies showed that in the presence of BUD, HP-ß-CD or BUD:HP-ß-CD complex, the association PL407-PL403 favored the gel formation close to the physiological temperature. Physico-chemical and in vitro release assays studies revealed no competitive displacement of BUD from the HP-ß-CD cavity evoked by PL407 or PL407-PL403 addition. These findings point out the BUD-HP-ß-CD in PL-based hydrogels as strategies for future investigations on development of new pharmaceutical formulations for the treatment of ulcerative colitis.

Transdermal delivery of butamben using elastic and conventional liposomes.

Gel formulations containing the local anesthetic butamben (BTB) encapsulated in either conventional (BTBLUV) or elastic (BTBLUV-EL) liposomes were prepared and characterized, and then evaluated in terms of their skin permeability. Parameters measured included vesicle size and surface charge, BTB fluorescence anisotropy, encapsulation efficiency, partition coefficient and liposomal membrane organization. Encapsulation efficiencies and membrane/water partition coefficients were determined using a phase separation. The partition coefficients of the elastic and conventional formulations were 2025 ± 234 and 1136 ± 241, respectively. The sizes of the elastic and conventional liposomes did not change significantly (p > 0.05) following incorporation of the anesthetic. As expected, the elastic liposomes presented order parameters that were lower than those of the conventional liposomes, as determined by electron paramagnetic resonance with a 5-stearic acid nitroxide probe incorporated into the bilayer. After 8 h, the fluxes into the receiving solution (µg/cm(2)/h) were 6.95 ± 1.60 (10% BTB), 23.17 ± 6.09 (10% BTBLUV) and 29.93 ± 6.54 (10% BTBLUV-EL). The corresponding time lags (h) were 1.90 ± 0.48, 1.23 ± 0.28 and 1.57 ± 0.38, respectively. The permeability coefficients (10(-3 )cm/h) were 1.02 ± 0.23, 2.96 ± 0.77 and 4.14 ± 0.9, for 10% BTB, 10% BTBLUV and 10% BTBLUV-EL, respectively. The results demonstrate that anesthetic access through the skin can be considerably enhanced using liposomal gel formulations, compared to plain gel formulations.

Local neurotoxicity and myotoxicity evaluation of cyclodextrin complexes of bupivacaine and ropivacaine.

BACKGROUND: Bupivacaine (BVC) and ropivacaine (RVC) are local anesthetics widely used in surgical procedures. In previous studies, inclusion complexes of BVC or RVC in hydroxypropyl-ß-cyclodextrin (HP-ß-CD) increased differential nervous blockade, compared to the plain anesthetic solutions. In this study we evaluated the local neural and muscular toxicity of these new formulations containing 0.5% BVC or RVC complexed with HP-ß-CD (BVC(HP-ß-CD) and RVC(HP-ß-CD)). METHODS: Schwann cell viability was assessed by determination of mitochondrial dehydrogenase activity, and histopathological evaluation of the rat sciatic nerve was used to identify local neurotoxic effects (48 hours and 7 days after the treatments). Evaluations of serum creatine kinase levels and the histopathology of rat gastrocnemius muscle (48 hours after treatment) were also performed. RESULTS: Schwann cell toxicity evaluations revealed no significant differences between complexed and plain local anesthetic formulations. However, use of the complexed local anesthetics reduced serum creatine kinase levels 5.5-fold, relative to the plain formulations. The differences were significant at P < 0.05 (BVC) and P < 0.01 (RVC). The histopathological muscle evaluation showed that differences between groups treated with local anesthetics (BVC or RVC) and their respective complexed formulations (BVC(HP-ß-CD) or RVC(HP-ß-CD)) were significant (P < 0.05). CONCLUSIONS: We concluded that the new formulations presented a lower myotoxicity and a similar cytotoxic effect when compared to plain local anesthetic solutions.

Sufentanil-2-hydroxypropyl-ß-cyclodextrin inclusion complex for pain treatment: physicochemical, cytotoxicity, and pharmacological evaluation.

Sufentanil (SUF) is a synthetic analgesic opioid widely used for the management of acute and chronic pain. This drug was complexed with 2-hydroxypropyl-ß-cyclodextrin (HP-ß-CD) and the physicochemical characterization, in vitro/ex vivo toxicity assays, and pharmacological evaluation were performed. Differential scanning calorimetry, Fourier transform infrared spectroscopy (FTIR) analysis, and X-ray powder diffraction showed the formation and the morphology of the complex. Nuclear magnetic resonance afforded data regarding inclusion complex stoichiometry (1:1) with an association binding constant (K(a)) value of 515.2 ± 1.2 M(-1) between SUF and HP-ß-CD. Complexation with HP-ß-CD protected SUF from light exposure and increased its photostability. Release kinetics revealed a decrease in SUF release rate (K(rel) = 7.05 ± 0.52 and 5.61 ± 0.39 min(-1/2) for SUF-HP-ß-CD and SUF, respectively) and reduced hemolytic or myotoxic effects after complexation. Time course of tail-flick test showed that the duration of analgesia induced by SUF (150.0 ± 34.6 min) was significantly increased (p < 0.001) after complexation with HP-ß-CD (355.7 ± 47.2 min) when injected at the same dose (1 µg kg(-1)), prolonging the duration of analgesia after intramuscular administration and representing an alternative on the development of effective and safe drug-delivery system for opioid analgesics.

Pharmacokinetic study of liposome-encapsulated and plain mepivacaine formulations injected intra-orally in volunteers.

OBJECTIVES: The pharmacokinetics of commercial and liposome-encapsulated mepivacaine (MVC) injected intra-orally in healthy volunteers was studied. METHODS: In this double blind, randomized cross-over study, 15 volunteers received, at four different sessions, 1.8 ml of the following formulations: 2% MVC with 1 : 100 000 epinephrine (MVC(2%EPI) ), 3% MVC (MVC(3%) ), 2% and 3% liposome-encapsulated MVC (MVC(2%LUV) and MVC(3%LUV) ). Blood samples were collected pre dose (0 min) and at 15, 30, 45, 60, 90, 120, 180, 240, 300, 360 min after injections. Liquid chromatography-tandem mass spectrometry was used to quantify plasma MVC concentrations. RESULTS: Pharmacokinetic analysis showed that the maximum plasma concentration (Cmax) and the areas under the curves (AUC(0-360) and AUC(0-∞)) after MVC(2%LUV) and MVC(2%EPI) injections were smaller (P < 0.05) than the equivalent figures for MVC(3%) and MVC(3%LUV). The time to maximum plasma concentration (Tmax) and the half-life of elimination (t½beta) obtained after the treatment with MVC(2%LUV), MVC(2%EPI), MVC(3%) and MVC(3%LUV) presented no statistically significant differences (P > 0.05). Cmax, AUC(0-360) and AUC(0-∞) after injection of the 2% formulations (MVC(2%LUV) and MVC(2%EPI) ) did not exhibit statistically significant differences (P > 0.05). The pharmacokinetics of MVC(2%LUV) were comparable to the pharmacokinetics of MVC(2%EPI). CONCLUSION: The liposomal formulation of 2% MVC exhibits similar systemic absorption to the local anesthetic with vasoconstrictor.

Improvement of tetracaine antinociceptive effect by inclusion in cyclodextrins.

Local anesthetics (LA) are among the most important pharmacological compounds used to attenuate or eliminate pain. However, systemic toxicity is still a limitation for LA application, especially for ester-type drugs, such as tetracaine (TTC) that presents poor chemical stability (due to hydrolysis by plasma esterases). Several approaches have been used to improve LA pharmaceutical properties, including the employment of drug-delivery systems. Here we used beta-cyclodextrin (ß-CD) or hydroxypropyl-beta-cyclodextrin (HP-ß-CD) to develop two new TTC formulations (TTC:ß-CD and TTC:HP-ß-CD). The inclusion complexes formation, in a 1:1 stoichiometry, was confirmed by differential scanning calorimetry, X-ray diffraction, UV-VIS absorption and fluorescence. Nuclear magnetic resonance (DOSY experiments) revealed that TTC association with HP-ß-CD is stronger (Ka=1200 mol/L(-1)) than with ß-CD (Ka=845 mol/L(-1)). Moreover, nuclear Overhauser effect (NOE) experiments provided information on the topology of the complexes, where TTC aromatic ring is buried inside the CD hydrophobic cavity. In vitro tests with 3T3 fibroblast cells culture revealed that complexation decreased TTC cytotoxicity. In addition, the total analgesic effect of TTC, tested in rats through the infraorbital nerve test, was improved in 36% with TTC:ß-CD and TTC:HP-ß-CD. In conclusion, these formulations presented potential for future clinical use, by reducing the toxicity and increasing the antinociceptive effect of tetracaine.

Bioadhesive films containing benzocaine: correlation between in vitro permeation and in vivo local anesthetic effect.

PURPOSE: The aim of this work was to develop anesthetic bioadhesive films containing benzocaine and study their in vitro skin permeation and in vivo performance, in comparison with commercial formulations. METHODS: Films containing 3% and 5% w/w of benzocaine were prepared and characterized by weight, drug content, thickness and morphology. In vitro permeation assays were performed in vertical diffusion cells using full-thickness pig ear skin as barrier. Intensity and duration of analgesia were evaluated in rats by tail-flick test, and skin histological analysis was carried out. RESULTS: Tail-flick test showed that the duration of benzocaine-induced analgesia was significantly prolonged with the films compared to commercial creams, in agreement with the higher in vitro permeation. Histological analysis of the rat tail skin did not reveal morphological tissue changes nor cell infiltration signs after application of the commercial creams or films. CONCLUSIONS: Results from our study indicate that the films developed in this work can be considered as innovative dermal/transdermal therapeutic systems for benzocaine local delivery.