Long-term effect of ropivacaine nanoparticles for sciatic nerve block on postoperative pain in rats

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.

Ultrasound-Triggered on Demand Lidocaine Release Relieves Postoperative Pain

Safe and non-invasive on-demand relief is a crucial and effective treatment for postoperative pain because it considers variable timing and intensity of anesthetics. Ultrasound modulation is a promising technique for this treatment because it allows convenient timed and non-invasive controlled drug release. Here, we created an ultrasound-triggered lidocaine (Lido) release platform using an amino acid hydrogel functioning as three-dimensional (3D) scaffold material (Lido-PPIX@ER hydrogel). It allows control of the timing, intensity and duration of lidocaine (Lido) to relieve postoperative pain. The hydrogel releases Lido due to the elevated reactive oxygen species (ROS) levels generated by PPIX under ultrasound triggering. The Lido-PPIX@ER hydrogel under individualized ultrasound triggering released lidocaine and provided effective analgesia for more than 72 h. The withdrawal threshold was higher than that in the control group at all time points measured. The hydrogel showed repeatable and adjustable ultrasound-triggered nerve blocks in vivo, the duration of which depended on the extent and intensity of insonation. On histopathology, no systemic effect or tissue reaction was observed in the ultrasound-triggered Lido-PPIX@ER hydrogel-treated group. The Lido-PPIX@ER hydrogel with individualized (highly variable) ultrasound triggering is a convenient and effective method that offers timed and spatiotemporally controlled Lido release to manage postoperative pain. This article presents the delivery system for a new effective strategy to reduce pain, remotely control pain, and offer timed and spatiotemporally controlled release of Lido to manage postoperative pain.

Micro- and nanocarriers for pain alleviation

Acute or chronic pain is a major source of impairment in quality of life and affects a substantial part of the population. To date, pain is alleviated by a limited range of treatments with significant toxicity, increased risk of misuse and inconsistent efficacy, owing, in part, to lack of specificity and/or unfavorable pharmacokinetic properties. Thanks to the unique properties of nanoscaled drug carriers, nanomedicine may enhance drug biodistribution and targeting, thus contributing to improved bioavailability and lower off-target toxicity. After a brief overview of the current situation and the main critical issues regarding pain alleviation, this review will examine the most advanced approaches using nanomedicine of each drug class, from the preclinical stage to approved nanomedicines.

Paeoniflorin ameliorates neuropathic pain-induced depression-like behaviors in mice by inhibiting hippocampal neuroinflammation activated via TLR4/NF-κB pathway

Neuropathic pain (NP) that contributes to the comorbidity between pain and depression is a clinical dilemma. Neuroinflammatory responses are known to have potentially important roles in the initiation of NP and depressive mood. In this study, we aimed to investigate the effects of paeoniflorin (PF) on NP-induced depression-like behaviors by targeting the hippocampal neuroinflammation through the toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB) signaling pathway. We used a murine model of NP caused by unilateral sciatic nerve cuffing (Cuff). PF was injected intraperitoneally once a day for a total of 14 days. Pain and depression-like behavior changes were evaluated via behavioral tests. Pathological changes in the hippocampus of mice were observed by H&E staining. The levels of proinflammatory cytokines in the hippocampus were detected using ELISA. Activated microglia were measured by immunohistochemical staining. The TLR4/NF-κB signaling pathway-associated protein expression in the hippocampus was detected by western blotting. We found that the PF could significantly alleviate Cuff-induced hyperalgesia and depressive behaviors, lessen the pathological damage to the hippocampal cell, reduce proinflammatory cytokines levels, and inhibit microglial over-activation. Furthermore, PF downregulated the expression levels of TLR4/NF-κB signaling pathway-related proteins in the hippocampus. These results indicate that PF is an effective drug for improving the comorbidity between NP and depression.

Degradable polymeric vehicles for postoperative pain management

Effective control of pain management has the potential to significantly decrease the need for prescription opioids following a surgical procedure. While extended release products for pain management are available commercially, the implementation of a device that safely and reliably provides extended analgesia and is sufficiently flexible to facilitate a diverse array of release profiles would serve to advance patient comfort, quality of care and compliance following surgical procedures. Herein, we review current polymeric systems that could be utilized in new, controlled post-operative pain management devices and highlight where opportunities for improvement exist.

Recent research and development of local anesthetic-loaded microspheres

This review introduces the recent research and development in local anesthetic-loaded microsphere, as efficient microspheres formulation, the efficient microspheres: optimum preparation method, high loading efficiency, and ideal release rate.

Topical anesthetic analgesic therapy using the combination of ropivacaine and dexmedetomidine: hyaluronic acid modified long-acting nanostructured lipid carriers containing a skin penetration enhancer

Purpose

Hyaluronic acid-poly(ethylene glycol)-distearoyl phosphoethanolamine (HA-PEG-DSPE) modified and tocopheryl polyethylene glycol 1000 succinate (TPGS) contained nanostructured lipid carriers (NLCs) were prepared loading ropivacaine and dexmedetomidine to improve the topical anesthetic analgesic anesthesia efficiency.

Methods

NLCs were prepared by the solvent diffusion method. The average particle size, zeta potential, release behavior, and cytotoxicity of the NLCs were tested. Ex vivo skin permeation was studied using a Franz diffusion cell mounted with depilated rat skin. Local anesthesia antinociceptive efficiency was evaluated by rat tail flick latency study in vivo.

Results

NLCs have sizes of about 100 nm, with negative zeta potentials. All the NLCs formulations were found to be significantly less cytotoxic than free drugs at equivalent concentrations. The cumulative amount of drugs penetrated through rat skin from NLCs was 2.0–4.7 folds higher than that of the drugs solution. The in vivo anesthesia antinociception study displayed that NLCs showed stronger and longer anesthesia antinociceptive effect when compared with single drugs loaded NLCs and drugs solution even at a lower dosage of drugs.

Conclusion

The results demonstrated that the HA modified, TPGS contained, dual drugs loaded NLCs could perform a synergistic effect and may reduce the amount of drugs, which can lower the toxicity of the system and at the meanwhile, increase the anesthesia antinociceptive efficiency.

Lidocaine Potentiates SOCS3 to Attenuate Inflammation in Microglia and Suppress Neuropathic Pain

Lidocaine is one of the typical local anesthetics that are frequently used in the peripheral nerve blocks and pain management. Emerging evidence have shown that lidocaine may exert anti-inflammatory effect involving neuropathic pain. However, the effect and underlying mechanism of lidocaine in suppressing neuroinflammation in neuropathic pain are incompletely revealed. In this study, effects of lidocaine on the suppressors of cytokine-signaling protein 3 (SOCS3) in microglia are investigated in chronic constriction injury (CCI) rat model and lipopolysaccharide (LPS)-stimulated BV-2 cells. It was shown that intrathecal injection of lidocaine substantially alleviated CCI-induced neuropathic pain, as reflected by the decreased thermal latency and mechanical threshold. Lidocaine reduced the CCI-evoked spinal injury and cell apoptosis. CCI induced an significant increase of IBA1⁺ microglia accompanied by the increase of inflammatory cytokines IL-6 and IL-1β, which were suppressed after lidocaine administration. SOCS3 expression in IBA1⁺ microglia was notably upregulated in response to lidocaine injection, which presented in a similar pattern in LPS-activated BV-2 cells. Furthermore, lidocaine upregulated SOCS3 expression dependent of pCREB, and CREB silencing greatly discounted this effect. The intrathecal injection of lentiviral vectors LV-SOCS3 efficiently alleviated CCI-evoked neuropathic pain and reduced spinal IBA1⁺ microglia. SOCS3 overexpression contributed to the inhibition of neuroinflammation by decreasing the expression and activation of p38 MAPK and NF-κB stimulated by LPS. Collectively, lidocaine promoted the SOCS3 expression in microglia, in turn leading to suppression of IBA1⁺ microglia accumulation and p38 MAPK and NF-κB, which may expand our understanding on lidocaine in suppressing neuroinflammation and neuropathic pain.

An efficient and long-acting local anesthetic: ropivacaine-loaded lipid-polymer hybrid nanoparticles for the control of pain

Purpose

Local anesthetics are used clinically for the control of pain following operation (including gastrointestinal surgery) or for the management of other acute and chronic pain. This study aimed to develop a kind of lipid-polymer hybrid nanoparticles (LPNs), which were constructed using poly(ethylene glycol)-distearoylphosphatidylethanolamine (PEG-DSPE) as the hydrophilic lipid shell and poly-ε-caprolactone (PCL) as the hydrophobic polymeric core.

Methods

Ropivacaine (RPV) was entrapped in the LPNs (RPV-LPNs) and the physicochemical and biochemical properties such as size, zeta potential, drug release, and cytotoxicity were studied. The long-lasting effects and safety aspects of the LPNs were evaluated in vitro and in vivo.

Results

The particle size and zeta potential of RPV-LPNs were 112.3±2.6 nm and −33.2±3.2 mV, with an entrapment efficiency (EE) of 90.2%±3.7%. Ex vivo permeation efficiency of LPNs was better than the drug solution. The RPV-LPNs exhibited a long-lasting in vivo anesthesia effect in both rats and mice.

Conclusion

Considering the low cytotoxicity, the LPNs prepared here could be used as an efficient local anesthetic for the control of pain.

Injectable nanocomposite analgesic delivery system for musculoskeletal pain management

Musculoskeletal pain is a major health issue which results from surgical procedures (i.e. total knee and/or hip replacements and rotator cuff repairs), as well as from non-surgical conditions (i.e. sympathetically-mediated pain syndrome and occipital neuralgia). Local anesthetics, opioids or corticosteroids are currently used for the pain management of musculoskeletal conditions. Even though local anesthetics are highly preferred, the need for multiple administration presents significant disadvantages. Development of unique delivery systems that can deliver local anesthetics at the injection site for prolonged time could significantly enhance the therapeutic efficacy and patient comfort. The goal of the present study is to evaluate the efficacy of an injectable local anesthetic nanocomposite carrier to provide sustained analgesic effect. The nanocomposite carrier was developed by encapsulating ropivacaine, a local anesthetic, in lipid nanocapsules (LNC-Rop), and incorporating the nanocapsules in enzymatically crosslinked glycol chitosan (0.3GC) hydrogels. Cryo Scanning Electron Microscopic (Cryo SEM) images showed the ability to distribute the LNCs within the hydrogel without adversely affecting their morphology. The study demonstrated the feasibility to achieve sustained release of lipophilic molecules from the nanocomposite carrier in vitro and in vivo. A rat chronic constriction injury (CCI) pain model was used to evaluate the efficacy of the nanocomposite carrier using thermal paw withdrawal latency (TWL). The nanocomposite carriers loaded with ropivacaine and dexamethasone showed significant improvement in pain response compared to the control groups for at least 7 days. The study demonstrated the clinical potential of these nanocomposite carriers for post-operative and neuropathic pain.

STATEMENT OF SIGNIFICANCE

Acute or chronic pain associated with musculoskeletal conditions is considered a major health issue, with healthcare costs totaling several billion dollars. The opioid crisis presents a pressing clinical need to develop alternative and effective approaches to treat musculoskeletal pain. The goal of this study was to develop a long-acting injectable anesthetic formulation which can sustain a local anesthetic effect for a prolonged time. This in turn could increase the quality of life and rehabilitation outcome of patients, and decrease opioid consumption. The developed injectable nanocomposite demonstrated the feasibility to achieve prolonged pain relief in a rat chronic constriction injury (CCI) model.