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.

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.

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.

Anesthetic efficacy and pain induced by dental anesthesia: the influence of gender and menstrual cycle

OBJECTIVE

To assess the influence of the menstrual cycle and oral contraceptives on pain sensitivity and local anesthetic effectiveness.

STUDY DESIGN

Thirty volunteers were designated into 3 groups (n = 10): group 1, women using contraceptives; group 2, women not using contraceptives; and group 3, men. Groups 1 and 2 had a buccal infiltration of 2% lidocaine with 1:100,000 epinephrine at the upper-right canine during each one of the 5 phases of the menstrual cycle and group 3 at a randomly selected day. Pain threshold, latency period, and pulpal anesthesia were measured with an electrical pulp tester. Injection discomfort was recorded. Data were analyzed with Friedman and Kruskal-Wallis tests.

RESULTS

Pain threshold was higher in men; however, there were no significant differences (P > .05) in anesthetic duration and injection discomfort.

CONCLUSION

Injection discomfort and clinical effectiveness of local anesthetics are not related to sex, phases of the menstrual cycle, or use of oral contraceptives.

Comparison of effectiveness of 4% articaine associated with 1: 100,000 or 1: 200,000 epinephrine in inferior alveolar nerve block

This comparative study using 20 healthy volunteers evaluated the anesthetic efficacy of 4% articaine in association with 2 different concentrations of epinephrine, 1:200,000 (G1) and 1:100,000 (G2). The first premolars were tested with a pulp tester to verify the anesthesia induced by the inferior alveolar nerve block. The following parameters were measured: period of latency (PL; interval between the end of anesthetic injection and absence of response to the maximum output--80 reading--of the pulp tester); complete pulpal anesthesia (CPA; period in which the subject had no response to maximal output of the pulp tester 80 reading); partial anesthesia (PA; interval between the first reading below 80 and the return to basal levels); and the anesthesia of the soft tissues (AST; period of time from onset of anesthesia until the return to normal sensation of the lip). The Wilcoxon test (alpha = 0.05) was used to analyze the data. No significant difference was found regarding PL (P = .47), CPA (P = .88), PA (P = .46), and AST (P = .85). The results indicated that both solutions presented the same clinical effectiveness in blocking the inferior alveolar nerve.