Characterization of exparel bupivacaine multivesicular liposomes

Advances in the use of local anesthetic extended-release systems in pain management

Pain management remains among the most common and largely unmet clinical problems today. Local anesthetics play an indispensable role in pain management. The main limitation of traditional local anesthetics is the limited duration of a single injection. To address this problem, catheters are often placed or combined with other drugs in clinical practice to increase the time that local anesthetics act. However, this method does not meet the needs of clinical analgesics. Therefore, many researchers have worked to develop local anesthetic extended-release types that can be administered in a single dose. In recent years, drug extended-release systems have emerged dramatically due to their long duration and efficacy, providing more possibilities for the application of local anesthetics. This paper summarizes the types of local anesthetic drug delivery systems and their clinical applications, discusses them in the context of relevant studies on local anesthetics, and provides a summary and outlook on the development of local anesthetic extended-release agents.

Microfluidic Preparation and Evaluation of Multivesicular Liposomes Containing Gastrodin for Oral Delivery across the Blood-Brain Barrier

In this study, multivesicular liposomes (MVLs) were prepared by microfluidic technology and used for delivering gastrodin (GAS), a water-soluble drug, across the blood-brain barrier (BBB). The formulations and preparation parameters in preparing gastrodin multivesicular liposomes (GAS-MVLs) were both optimized. Some properties of GAS-MVLs including morphology, particle size, encapsulation efficiency, and in vitro release were evaluated. An in vitro BBB model was established by coculturing mouse brain endothelial cells (bEnd.3) and astrocytes (C8-D1A). The permeability of GAS-MVLs across the BBB model was evaluated. Finally, the permeability of GAS-MVLs across BBB was evaluated by in vivo pharmacokinetics in mice. The concentrations of GAS in the blood and brain were determined by high-performance liquid chromatography (HPLC), and then brain-targeting efficiency (BTE), relative uptake rate (Re), and peak concentration ratio (Ce) were calculated. The results showed that, using a Y-type microfluidic chip and setting the flow rate ratio of the second aqueous phase to the W/O emulsion phase at 23, with a total flow rate of 0.184 m/s, the prepared GAS-MVLs showed an obvious multivesicular structure and a relatively narrow distribution of particle sizes. The prepared GAS-MVLs were spherical with a dense structure. The average particle size was 2.09 ± 0.17 μm. The average encapsulation rate was (34.47 ± 0.39)%. The particle size of MVLs prepared by the microfluidic method was much smaller than that prepared by the traditional method, which was usually larger than 10 μm. After 6 h from the beginning of the administration, the apparent transmittance of GAS-MVLs in the in vitro BBB model was 67.71%, which was 1.92 times higher than that of the GAS solution. In vivo pharmacokinetic study showed that the intracerebral area under curve (AUC) of GAS-MVLs was 5.68 times higher than that of the GAS solution, and the e peak concentration (Cmax) was 2.036 times higher than that of the GAS solution. BTE was 1.945, intracerebral Re was 5.688, and Ce was 2.036. Both in vitro and in vivo experiment results showed that GAS-MVLs prepared by microfluidic technology in this study significantly delivered GAS across BBB and enriched GAS in the brain. It provides a possibility for brain-targeting delivery of GAS in the prevention and treatment of central nervous system diseases by oral administration and lays the foundation for further development of oral brain-targeted preparations of GAS.

Immune Implications of Cholesterol-Containing Lipid Nanoparticles

The majority of clinically approved nanoparticle-mediated therapeutics are lipid nanoparticles (LNPs), and most of these LNPs are liposomes containing cholesterol. LNP formulations significantly alter the drug pharmacokinetics (PK) due to the propensity of nanoparticles for uptake by macrophages. In addition to readily engulfing LNPs, the high expression of cholesterol hydroxylases and reactive oxygen species (ROS) in macrophages suggests that they will readily produce oxysterols from LNP-associated cholesterol. Oxysterols are a heterogeneous group of cholesterol oxidation products that have potent immune modulatory effects. Oxysterols are implicated in the pathogenesis of atherosclerosis and certain malignancies; they have also been found in commercial liposome preparations. Yet, the in vivo metabolic fate of LNP-associated cholesterol remains unclear. We review herein the mechanisms of cellular uptake, trafficking, metabolism, and immune modulation of endogenous nanometer-sized cholesterol particles (i.e., lipoproteins) that are also relevant for cholesterol-containing nanoparticles. We believe that it would be imperative to better understand the in vivo metabolic fate of LNP-associated cholesterol and the immune implications for LNP-therapeutics. We highlight critical knowledge gaps that we believe need to be addressed in order to develop safer and more efficacious lipid nanoparticle delivery systems.

Construction of injectable micron-sized polymorphic vesicles for prolonged local anesthesia with weekly sustained release of ropivacaine

Currently, to overcome the short half-life of the local anesthetic ropivacaine, drug delivery systems such as nanoparticles and liposomes have been used to prolong the analgesic effect, but they are prone to abrupt release from the site of administration or have poor slow-release effects, which increases the risk of cardiotoxicity. In this study, injectable lipid suspensions based on ropivacaine-docusate sodium hydrophobic ion pairing (HIP) were designed to significantly prolong the duration of analgesia. The resulting ion-paired lipid suspension (HIP/LIPO) had a micrometer scale and a high zeta potential, which facilitates stable in situ retention. The strong interaction between docusate sodium and ropivacaine was verified using thermal and spectroscopic analyses, and the formation of micron-sized polymorphic vesicles was attributed to the mutual stabilizing interactions between ropivacaine-docusate sodium HIP, docusate sodium and lecithin. The HIP/LIPO delivery system could maintain drug release for more than 5 days in vitro and achieve high analgesic efficacy for more than 10 days in vivo, reducing the side effects associated with high drug doses. The stable HIP/LIPO delivery system is a promising strategy that offers a clinically beneficial alternative for postoperative pain management and other diseases.

Extended Release of Bupivacaine from Temperature-Responsive PNDJ Hydrogels Improves Postoperative Weight-Bearing in Rabbits Following Knee Surgery

Effective treatment of postoperative pain lasting for multiple days without opioids is an important clinical need. We previously reported analgesia lasting up to 96 h in a porcine soft tissue model of postoperative pain using SBG004, an extended-release formulation of bupivacaine based on the temperature-responsive polymer poly(N-isopropylacrylamide-co-dimethylbutyrolactone acrylamide-co-Jeffamine M-1000 acrylamide) [PNDJ]. Orthopaedic surgical sites such as the knee can involve complex sensory innervation which presents a distinct challenge to local anesthetic delivery. The purpose of this work was to evaluate the pharmacokinetics and efficacy of SBG004 in an orthopaedic surgical model in comparison to currently available local anesthetics. Pharmacokinetics following periarticular (PA) or intraarticular (IA) injection of SBG004 were compared against liposomal bupivacaine (Lip-Bupi) PA in New Zealand White rabbits (all doses 14.5 mg/kg). Analgesic efficacy of SBG004 (IA, PA, or IA + PA), three active comparators, and saline was evaluated following knee surgery in New Zealand White rabbits. Analgesia was assessed via weight-bearing on the operated limb during spontaneous large steps in video recordings. Systemic bupivacaine exposure lasted at least 7 days for SBG004 PA, 4 days for SBG004 IA, and 2 days for Lip-Bupi PA. In the analgesia study, weight-bearing in all active groups except SBG004 IA was more frequent versus saline through 8 h postoperatively (p < 0.05). Only SBG004 IA + PA resulted in a higher proportion of weight-bearing rabbits at 24 h versus saline (6/7 versus 2/10, p = 0.015). Analysis of pooled data from 24-72 h showed significantly greater frequency of weight-bearing in rabbits receiving SBG004 IA + PA (71%) versus saline (37%), ropivacaine cocktail (41%), and Lip-Bupi PA (36%). The results indicate that the release profile from SBG004 PA or IA coincides reasonably with the time course of postoperative pain, and SBG004 may produce longer duration of analgesia than local anesthetics currently used in knee surgery, including during the period of 24-72 h recognized as a target for extended-release local anesthetics.

Targeted local anesthesia: a novel slow-release Fe3O4-lidocaine-PLGA microsphere endowed with a magnetic targeting function

PURPOSE

Lidocaine microspheres can prolong the analgesic time to 24-48 h, which still cannot meet the need of postoperative analgesia lasting more than 3 days. Therefore, we added Fe3O4 to the lidocaine microspheres and used an applied magnetic field to attract Fe3O4 to fix the microspheres around the target nerves, reducing the diffusion of magnetic lidocaine microspheres to the surrounding tissues and prolonging the analgesic time.

METHODS

Fe3O4-lidocaine-PLGA microspheres were prepared by the complex-emulsion volatilization method to characterize and study the release properties in vitro. The neural anchoring properties and in vivo morphology of the drug were obtained by magnetic resonance imaging. The nerve blocking effect and analgesic effect of magnetic lidocaine microspheres were evaluated by animal experiments.

RESULTS

The mean diameter of magnetically responsive lidocaine microspheres: 9.04 ± 3.23 μm. The encapsulation and drug loading of the microspheres were 46.18 ± 3.26% and 6.02 ± 1.87%, respectively. Magnetic resonance imaging showed good imaging of Fe3O4-Lidocain-PLGA microspheres, a drug-carrying model that slowed down the diffusion of the microspheres in the presence of an applied magnetic field. Animal experiments demonstrated that this preparation had a significantly prolonged nerve block, analgesic effect, and a nerve anchoring function.

CONCLUSION

Magnetically responsive lidocaine microspheres can prolong analgesia by slowly releasing lidocaine, which can be immobilized around the nerve by a magnetic field on the body surface, avoiding premature diffusion of the microspheres to surrounding tissues and improving drug targeting.

Revisiting the in-vitro and in-vivo considerations for in-silico modelling of complex injectable drug products

Complex injectable drug products (CIDPs) have often been developed to modulate the pharmacokinetics along with efficacy for therapeutic agents used for remediation of chronic disorders. The effective development of CIDPs has exhibited complex kinetics associated with multiphasic drug release from the prepared formulations. Consequently, predictability of pharmacokinetic modelling for such CIDPs has been difficult and there is need for advanced complex computational models for the establishment of accurate prediction models for in-vitro-in-vivo correlation (IVIVC). The computational modelling aims at supplementing the existing knowledge with mathematical equations to develop formulation strategies for generation of predictable and discriminatory IVIVC. Such an approach would help in reduction of the burden of effect of hidden factors on preclinical to clinical translations. Computational tools like physiologically based pharmacokinetics (PBPK) modelling have combined physicochemical and physiological properties along with IVIVC characteristics of clinically used formulations. Such techniques have helped in prediction and understanding of variability in pharmacodynamic parameters of potential generic products to clinically used formulations like Doxil®, Ambisome®, Abraxane® in healthy and diseased population using mathematical equations. The current review highlights the important formulation characteristics, in-vitro, preclinical in-vivo aspects which need to be considered while developing a stimulatory predictive PBPK model in establishment of an IVIVC and in-vitro-in-vivo relationship (IVIVR).