Concurrent versus delayed exposure to corticosteroids in equine articular tissues cultured with local anesthetic.

OBJECTIVE: To determine the effect of concurrent versus delayed treatment with corticosteroid on equine articular tissues also treated with local anesthetic in vitro in the presence of inflammatory mediators. STUDY DESIGN: Controlled laboratory study. ANIMALS: Five geldings, one mare (aged 3-18 years). METHODS: From each horse, 24 synovial and 12 osteochondral explants were cultured in a 12-well plate (2 wells/group, 2 synovial and 1 osteochondral explant/well, total 216 explants in the study). Explants were stimulated in culture medium with 10 µg/ml recombinant equine interleukin-1ß and 10 µg/ml tumor necrosis factor-α for 48 hours, then randomly assigned to six treatments: unstimulated control, stimulated control, triamcinolone acetonide (TA, 10-6  M), mepivacaine hydrochloride (MH, 4.4 mg/ml), MH + TA (concurrent) and MH + TA (delayed). The delayed group was treated with MH and, 6 days later, treated with TA. Every 3 days for 9 days total, medium levels of lactate dehydrogenase (LDH), prostaglandin E2 (PGE2 ), matrix metalloproteinase 13 (MMP-13) and glycosaminoglycan (GAG) were quantified via ELISA. Data were analyzed with mixed-effects models with Tukey's multiple comparisons. RESULTS: Stimulation increased medium PGE2 and MMP-13 and had no effect on LDH or GAG. Treatment with MH increased LDH and decreased PGE2 and MMP-13. Treatment with TA decreased PGE2 and MMP-13. CONCLUSION: There were no differences in cytotoxicity, inflammation or matrix degradation for delayed or concurrent MH and TA treatment groups up to 9 days in culture. CLINICAL SIGNIFICANCE: The lack of an effect of concurrent versus delayed treatment might indicate that concurrent therapy is acceptable.

Local anesthetics elicit immune-dependent anticancer effects.

BACKGROUND: Retrospective clinical trials reported a reduced local relapse rate, as well as improved overall survival after injection of local anesthetics during cancer surgery. Here, we investigated the anticancer effects of six local anesthetics used in clinical practice. RESULTS: In vitro, local anesthetics induced signs of cancer cell stress including inhibition of oxidative phosphorylation, and induction of autophagy as well as endoplasmic reticulum (ER) stress characterized by the splicing of X-box binding protein 1 (XBP1s) mRNA, cleavage of activating transcription factor 6 (ATF6), phosphorylation of eIF2α and subsequent upregulation of activating transcription factor 4 (ATF4). Both eIF2α phosphorylation and autophagy required the ER stress-relevant eukaryotic translation initiation factor 2 alpha kinase 3 (EIF2AK3, best known as PERK). Local anesthetics also activated two hallmarks of immunogenic cell death, namely, the release of ATP and high-mobility group box 1 protein (HMGB1), yet failed to cause the translocation of calreticulin (CALR) from the ER to the plasma membrane. In vivo, locally injected anesthetics decreased tumor growth and improved survival in several models of tumors established in immunocompetent mice. Systemic immunotherapy with PD-1 blockade or intratumoral injection of recombinant CALR protein, increased the antitumor effects of local anesthetics. Local anesthetics failed to induce antitumor effects in immunodeficient mice or against cancers unable to activate ER stress or autophagy due to the knockout of EIF2AK3/PERK or ATG5, respectively. Uncoupling agents that inhibit oxidative phosphorylation and induce autophagy and ER stress mimicked the immune-dependent antitumor effects of local anesthetics. CONCLUSION: Altogether, these results indicate that local anesthetics induce a therapeutically relevant pattern of immunogenic stress responses in cancer cells.

Comparison of Liposomal Bupivacaine and Conventional Local Anesthetic Agents in Regional Anesthesia: A Systematic Review.

BACKGROUND: Pain is one of the most common adverse events after surgery. Regional anesthesia techniques are effective for pain control but have limited duration of action. Liposomal bupivacaine is a long-acting formulation of bupivacaine. We conduct this systematic review to assess whether liposomal bupivacaine may prolong the analgesic duration of regional anesthesia compared to conventional local anesthetic agents. METHODS: We systematically searched PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), EMBASE (Ovid), Cumulative Index to Nursing and Allied Health Literature (CINAHL), Google Scholar, Web of Science citation index, US clinical trials register, and recent conference abstracts for relevant studies. RESULTS: We identified 13 randomized controlled trials that compared the use of liposomal bupivacaine to conventional local anesthetics in regional anesthesia. There were 5 studies on transversus abdominis plane (TAP) block, 3 of which reported longer duration of analgesia with liposomal bupivacaine. One study reported comparable analgesia with liposomal bupivacaine TAP block compared to TAP block catheter. There were 3 studies on brachial plexus block, 2 of which reported that liposomal bupivacaine may provide longer analgesia. Studies on other techniques did not report significantly longer analgesia with liposomal bupivacaine. CONCLUSIONS: Currently, there is limited evidence suggesting that liposomal bupivacaine provides longer analgesia than conventional local anesthetics when used in regional anesthesia. The analyses of multiple studies on liposomal bupivacaine for TAP blocks and brachial plexus blocks have yielded conflicting results. As a result, no definitive conclusions can be drawn about its efficacy compared to plain bupivacaine.

Laser-induced transient skin disruption to enhance cutaneous drug delivery.

The use of pressure waves (PW) to disrupt the stratum corneum (SC) temporarily is an effective strategy to increase the deposition of drug molecules into the skin. However, given the rather modest outcomes when compared with ablation-assisted drug delivery, its potential has been underestimated. Accordingly, the aim of this study was to examine the impact of Resonant Amplitude Waves (RAWs) on increasing cutaneous delivery. RAW phenomena are triggered by focusing a high-peak-power pulsed laser onto an appropriate transducer structure, under space- and time-controlled resolution. In order to determine the optimal conditions for the generation and use of RAWs, a screening of laser parameters setting and an analysis of different geometries of the impact pattern over diverse materials used as transducers was performed, analyzing the footprint of the RAW waves in an agarose gel. The results obtained were then checked and fine-tuned using human skin samples instead of agarose. Furthermore, ex vivo experiments were carried out to characterize the effect of the RAWs in the cutaneous delivery of diclofenac (DIC) and lidocaine (LID) administered in the form of gels. The application of RAWs resulted in an increased delivery of DIC and LID to the skin, whose intensity was dependent on the composition of the formulation. In fact, the maximum observed for DIC and LID in short-time experiments (39.1 ± 11.1 and 153 ± 16 µg/cm2, respectively) was comparable to those observed using ablation-assisted drug delivery under the same conditions. In conclusion, the combination of RAWs with specific formulation strategies is a feasible alternative for the cutaneous delivery of drug candidates when short onset of action is required.

The effect of extracorporeal shockwave on liposomal bupivacaine in a tibial plateau leveling osteotomy model.

OBJECTIVE: To determine the effect of extracorporeal shock wave (ESWT) on liposomal bupivacaine in a tibial-plateau-leveling osteotomy model. STUDY DESIGN: In vitro study. SAMPLE POPULATION: Ten samples per group. METHODS: In addition to a control group (sham treatment), five treatment groups were defined as A, energy (E) 3 (0.22 mJ/mm2 ), 360 pulses per minute (p/m); B, E6 (0.29 mJ/mm2 ), 360 p/m; C, E8 (0.39 mJ/mm2 ), 360 p/m; D, E6, 480 p/m; E, E8 480 p/m. Two-milliliter aliquots of liposomal bupivacaine were placed in a gelatin chamber and treated with 1000 pulses according to group. All samples remained in the chamber for 170 seconds to reflect the longest treatment group. Free bupivacaine concentrations were determined after treatment with high-performance liquid chromatography. RESULTS: The median free bupivacaine concentration was reported as control, 1.90 mg/mL; A, 2.10 mg/mL; B, 2.03 mg/mL; C, 2.94 mg/mL; D, 2.71 mg/mL; E, 4.35 mg/mL. Groups C (P = .027), D (P = .034), and E (P = .002) were different from the control group. Groups C (P = .0025) and D (P = .0025) were different from group E. Additional intertreatment group differences were found. CONCLUSION: Extracorporeal shock wave therapy caused a dose-dependent release of bupivacaine; however, there was no significant release of bupivacaine from liposomes when ESWT was applied at currently recommended therapeutic settings in this model. CLINICAL SIGNIFICANCE: This in vitro study provides evidence that concurrent electrohydraulic ESWT and liposomal bupivacaine is likely safe at currently recommended settings, however, higher energy and pulse frequency settings should be avoided.

A comparison of effects of scalp nerve block and local anesthetic infiltration on inflammatory response, hemodynamic response, and postoperative pain in patients undergoing craniotomy for cerebral aneurysms: a randomized controlled trial.

BACKGROUND: The purpose of this study was to compare the effects of scalp nerve block (SNB) and local anesthetic infiltration (LA) with 0.75% ropivacaine on postoperative inflammatory response, intraoperative hemodynamic response, and postoperative pain control in patients undergoing craniotomy. METHODS: Fifty-seven patients were admitted for elective craniotomy for surgical clipping of a cerebral aneurysm. They were randomly divided into three groups: Group S (SNB with 15 mL of 0.75% ropivacaine), group I (LA with 15 mL of 0.75% ropivacaine) and group C (that only received routine intravenous analgesia). Pro-inflammatory cytokine levels in plasma for 72 h postoperatively, hemodynamic response to skin incision, and postoperative pain intensity were measured. RESULTS: The SNB with 0.75% ropivacaine not only decreased IL-6 levels in plasma 6 h after craniotomy but also decreased plasma CRP levels and increased plasma IL-10 levels 12 and 24 h after surgery compared to LA and routine analgesia. There were significant increases in mean arterial pressure 2 and 5 mins after the incision and during dura opening in Groups I and C compared with Group S. Group S had lower postoperative pain intensity, longer duration before the first dose of oxycodone, less consumption of oxycodone and lower incidence of PONV through 48 h postoperatively than Groups I and C. CONCLUSION: Preoperative SNB attenuated inflammatory response to craniotomy for cerebral aneurysms, blunted the hemodynamic response to scalp incision, and controlled postoperative pain better than LA or routine analgesia. TRIAL REGISTRATION: Clinicaltrials.gov NCT03073889 (PI:Xi Yang; date of registration:08/03/2017).

Citrem-phosphatidylcholine nano-self-assemblies: solubilization of bupivacaine and its role in triggering a colloidal transition from vesicles to cubosomes and hexosomes.

Improvement of pain management strategies after arthroscopic surgery by multimodal analgesia may include the use of long-acting amide local anesthetics. Among these anesthetics, the low molecular weight local anesthetic agent bupivacaine (BUP) is attractive for use in postoperative pain management. However, it has a relatively short duration of action and imposes a higher risk of systemic toxicity at relatively large bolus doses. Bupivacaine encapsulation in lipid-based delivery systems is an attractive strategy for prolonging its local anaesthetic effect and reducing the associated undesirable systemic side effects. Here, we discuss the potential development of liquid crystalline nanocarriers for delivering BUP by using a binary lipid mixture of citrem and soy phosphatidylcholine (SPC) at different weight ratios. The produced safe-by-design family of citrem/SPC nanoparticles is attractive for use in the development of nanocarriers owing to the previously reported hemocompatibility. BUP encapsulation efficiency (EE), depending on the lipid composition, was in the range of 65-77%. In this study, nanoparticle tracking analysis (NTA) and synchrotron small-angle X-ray scattering (SAXS) were employed to gain insight into the effect of BUP solubilization and lipid composition on the size and structural characteristics of the produced citrem/SPC nanodispersions. BUP loading led to a slight change in the mean sizes (diameters) and size distributions of citrem/SPC nanoparticles. However, we found that BUP accommodation into the self-assembled interiors of nanoparticles, triggers significant structural alterations in BUP concentration- and lipid composition-dependent manners, which involve vesicle-cubosome and vesicle-hexosome transitions. The structural tunability of citrem/SPC nanoparticles and the implications for potential applications in intra-articular BUP delivery are discussed.

The Effect of Dexmedetomidine on Oral Mucosal Blood Flow and the Absorption of Lidocaine.

Dexmedetomidine (DEX) is a sedative and analgesic agent that acts via the alpha-2 adrenoreceptor and is associated with reduced anesthetic requirements, as well as attenuated blood pressure and heart rate in response to stressful events. A previous study reported that cat gingival blood flow was controlled via sympathetic alpha-adrenergic fibers involved in vasoconstriction. In the present study, experiment 1 focused on the relationship between the effects of DEX on alpha adrenoreceptors and vasoconstriction in the tissues of the oral cavity and compared the palatal mucosal blood flow (PMBF) in rabbits between general anesthesia with sevoflurane and sedation with DEX. We found that the PMBF was decreased by DEX presumably because of the vasoconstriction of oral mucosal vessels following alpha-2 adrenoreceptor stimulation by DEX. To assess if this vasoconstriction would allow decreased use of locally administered epinephrine during DEX infusion, experiment 2 in the present study monitored the serum lidocaine concentration in rabbits to compare the absorption of lidocaine without epinephrine during general anesthesia with sevoflurane and sedation with DEX. The depression of PMBF by DEX did not affect the absorption of lidocaine. We hypothesize that this is because lidocaine dilates the blood vessels, counteracting the effects of DEX. In conclusion, despite decreased palatal blood flow with DEX infusion, local anesthetics with vasoconstrictors should be used in implant and oral surgery even with administered DEX.

Real-time view of anesthetic solution spread during an ultrasound-guided thoracic paravertebral block.

BACKGROUND: Thoracic paravertebral block is a technique for perioperative analgesia in patients undergoing thoracic, chest wall, or breast surgery, or for pain management with rib fractures, which can be performed with or without ultrasound guidance. The ultrasound guidance technique can be used to identify the thoracic paravertebral space, guide needle placement, monitor the spread of local anesthetic (LA) solution, and reduce complications such as pleural puncture and pneumothorax. The possibility of assessing anesthetic spread in real time using ultrasound guidance during paravertebral block offers numerous advantages, including the immediate and accurate identification of the extent of nervous block, with a consequent reduction of LA dose. The real-time visualization of spread may be used to achieve good anesthetic cover by administering the block at a single level, thus reducing complications normally associated with the technique. CASE SUMMARY: This case report describes the use of ultrasound-guided thoracic paravertebral block, at thoracic (T) 4 and 5 levels, in a patient undergoing breast surgery for perioperative analgesia. The authors were able to witness cranial diffusion of LA at T3-T4 in real time, and measure the increase in space between the costotransverse ligament and pleura, as an indication of anesthetic spread, at T2-T3 and T6-T7 levels. CONCLUSIONS: This is the first known case in the literature of direct viewing of LA diffusion in a paravertebral space other than the one in which the block is administered and may open important scenarios for the improvement of anesthesia technique.

The Lateral Femoral Cutaneous Nerve: Description of the Sensory Territory and a Novel Ultrasound-Guided Nerve Block Technique.

BACKGROUND AND OBJECTIVES: Nerve blockade of the lateral femoral cutaneous (LFC) nerve provides some analgesia after hip surgery. However, knowledge is lacking about the extent of the cutaneous area anesthetized by established LFC nerve block techniques, as well as the success rate of anesthetic coverage of various surgical incisions. Nerve block techniques that rely on ultrasonographic identification of the LFC nerve distal to the inguinal ligament can be technically challenging. Furthermore, the branching of the LFC nerve is variable, and it is unknown if proximal LFC nerve branches are anesthetized using the current techniques. The primary aim of this study was to investigate a novel ultrasound-guided LFC nerve block technique based on injection into the fat-filled flat tunnel (FFFT), which is a duplicature of the fascia lata between the sartorius and the tensor fasciae latae muscle, in order to assess the success rate of anesthetizing the proximal LFC nerve branches and covering of the different surgical incisions used for hip surgery. METHODS: First, a cadaveric study was conducted in order to identify an FFFT injection technique that would provide adequate injectate spread to the proximal LFC nerve branches. Second, a clinical study was conducted in a group of 20 healthy volunteers over 2 consecutive days. On trial day 1, successful complete anesthesia of the LFC nerve was defined by performing a suprainguinal fascia iliaca block bilaterally in each subject. On trial day 2, a triple-blind randomized controlled trial compared the effect of the novel ultrasound-guided LFC nerve block technique for bupivacaine versus placebo. The primary end point was the success rate of anesthesia of the proximal cutaneous area innervated by the LFC nerve for the FFFT injection with bupivacaine versus placebo. RESULTS: Adequate spread of injectate to the proximal LFC nerve branches in cadavers was obtained by injecting 10 mL with dynamic needle-tip tracking in the FFFT. Application of this technique in the randomized controlled trial provided anesthesia of the lateral thigh with a success rate of 95% (95% confidence interval, 73.9%-99.8%) for the active side and 0% for placebo (P < 0.001). The proximal branches were anesthetized with a success rate of 68% (95% confidence interval, 43.4%-87.4%) on the active side. The proximal extent of the anesthetized cutaneous area was on average 7.9 cm distal to the greater trochanter. CONCLUSIONS: This novel LFC nerve block technique is easy and quick and reliably produces anesthesia of the lateral thigh. The greater trochanter is rarely included in the area of anesthesia, which reduces the coverage of each specific surgical incision. The success rate of 68% in anesthetizing the proximal nerve branches must be further evaluated by future research.

Subcellular Partitioning and Intramacrophage Selectivity of Antimicrobial Compounds against Mycobacterium tuberculosis.

The efficacy of antimicrobial drugs against Mycobacterium tuberculosis, an intracellular bacterial pathogen, is generally first established by testing compounds against bacteria in axenic culture. However, inside infected macrophages, bacteria encounter an environment which differs substantially from broth culture and are subject to important host-dependent pharmacokinetic phenomena which modulate drug activity. Here, we describe how pH-dependent partitioning drives asymmetric antimicrobial drug distribution in M. tuberculosis-infected macrophages. Specifically, weak bases with moderate activity against M. tuberculosis (fluoxetine, sertraline, and dibucaine) were shown to accumulate intracellularly due to differential permeability and relative abundance of their ionized and nonionized forms. Nonprotonatable analogs of the test compounds did not show this effect. Neutralization of acidic organelles directly with ammonium chloride or indirectly with bafilomycin A1 partially abrogated the growth restriction of these drugs. Using high-performance liquid chromatography, we quantified the degree of accumulation and reversibility upon acidic compartment neutralization in macrophages and observed that accumulation was greater in infected than in uninfected macrophages. We further demonstrate that the efficacy of a clinically used compound, clofazimine, is augmented by pH-based partitioning in a macrophage infection model. Because the parameters which govern this effect are well understood and are amenable to chemical modification, this knowledge may enable the rational development of more effective antibiotics against tuberculosis.

Autophagy activated by tuberin/mTOR/p70S6K suppression is a protective mechanism against local anaesthetics neurotoxicity.

The local anaesthetics (LAs) are widely used for peripheral nerve blocks, epidural anaesthesia, spinal anaesthesia and pain management. However, exposure to LAs for long duration or at high dosage can provoke potential neuronal damages. Autophagy is an intracellular bulk degradation process for proteins and organelles. However, both the effects of LAs on autophagy in neuronal cells and the effects of autophagy on LAs neurotoxicity are not clear. To answer these questions, both lipid LAs (procaine and tetracaine) and amide LAs (bupivacaine, lidocaine and ropivacaine) were administrated to human neuroblastoma SH-SY5Y cells. Neurotoxicity was evaluated by MTT assay, morphological alterations and median death dosage. Autophagic flux was estimated by autolysosome formation (dual fluorescence LC3 assay), LC3-II generation and p62 protein degradation (immunoblotting). Signalling alterations were examined by immunoblotting analysis. Inhibition of autophagy was achieved by transfection with beclin-1 siRNA. We observed that LAs decreased cell viability in a dose-dependent manner. The neurotoxicity of LAs was tetracaine > bupivacaine > ropivacaine > procaine > lidocaine. LAs increased autophagic flux, as reflected by increases in autolysosome formation and LC3-II generation, and decrease in p62 levels. Moreover, LAs inhibited tuberin/mTOR/p70S6K signalling, a negative regulator of autophagy activation. Most importantly, autophagy inhibition by beclin-1 knockdown exacerbated the LAs-provoked cell damage. Our data suggest that autophagic flux was up-regulated by LAs through inhibition of tuberin/mTOR/p70S6K signalling, and autophagy activation served as a protective mechanism against LAs neurotoxicity. Therefore, autophagy manipulation could be an alternative therapeutic intervention to prevent LAs-induced neuronal damage.

The Combination of IV and Perineural Dexamethasone Prolongs the Analgesic Duration of Intercostal Nerve Blocks Compared with IV Dexamethasone Alone.

Objective: The use of multiple-level, single-injection intercostal nerve blocks for pain control following video-assisted thorascopic surgery (VATS) is limited by the analgesic duration of local anesthetics. This study examines whether the combination of perineural and intravenous (IV) dexamethasone will prolong the duration of intraoperatively placed intercostal nerve blocks following VATS compared with IV dexamethasone and a perineural saline placebo. Design: Prospective, double-blind, randomized placebo-controlled trial. Setting: Single level-1 academic trauma center. Subjects: Forty patients undergoing a unilateral VATS under the care of a single surgeon. Methods: Patients were randomly assigned to two groups and received an intercostal nerve block containing 1) 0.5% bupivacaine with epinephrine and 1 ml of 0.9% saline or 2) 0.5% bupivacaine with epinephrine and 1 ml of a 4 mg/ml dexamethasone solution. All patients received 8 mg of IV dexamethasone. Results: Group 2 had lower NRS-11 scores at post-operative hours 8 (5.05, SD = 2.13 vs 3.50, SD = 2.50; p = 0.04), 20 (4.30, SD = 2.96 vs 2.26, SD = 2.31; p = 0.02), and 24 (4.53, SD = 1.95 vs 2.26, SD = 2.31; p = 0.02). Equianalgesic opioid requirement was decreased in group 2 at 32 hours (5.78 mg, SD = 5.77 vs 1.67 mg, SD = 3.49; p = 0.02). Group 2 also had greater FEV1 measured at 8, 12, 24, and 44 hours; greater FVC at 24 hours; greater PEF at 28 through 48 hours; and greater FEV1/FVC at 8 and 36 hours. Conclusions: The combination of IV and perineural dexamethasone prolonged the duration of a single-injection bupivacaine intercostal nerve block as measured by NRS-11 compared with IV dexamethasone alone at 24 hours. Reduced NRS-11 at other times, reduced opioid requirements, and increased PFTs were observed in group 2.

Hyaluronidase: from clinical applications to molecular and cellular mechanisms.

Over the past 60 years, hyaluronidase has been successfully utilized in ophthalmic surgery and is now being implemented in dermatosurgery as well as in other surgical disciplines. The enzyme is considered a "spreading factor" as it decomplexes hyaluronic acid (also called hyaluronan, HA), an essential component of the extracellular matrix (ECM). When applied as an adjuvant, hyaluronidase enhances the diffusion capacity and bioavailability of injected drugs. Therefore, the enzyme has been used as a local adjuvant to increase the diffusion capacity of local anesthetics, increasing the analgesic efficacy, and the anesthetized area particularly in the first minutes following injection, resulting in diminished intra- and postoperative pain. In aesthetic medicine, the off-label use of hyaluronidase is considered the gold standard for the management of HA-filler-associated complications. Here, we review the clinical use, underlying biological mechanisms, and future directions for the application of hyaluronidase in surgical and aesthetic medicine.

Lidocaine preferentially inhibits the function of purinergic P2X7 receptors expressed in Xenopus oocytes.

BACKGROUND: Lidocaine has been widely used to relieve acute pain and chronic refractory pain effectively by both systemic and local administration. Numerous studies reported that lidocaine affects several pain signaling pathways as well as voltage-gated sodium channels, suggesting the existence of multiple mechanisms underlying pain relief by lidocaine. Some extracellular adenosine triphosphate (ATP) receptor subunits are thought to play a role in chronic pain mechanisms, but there have been few studies on the effects of lidocaine on ATP receptors. We studied the effects of lidocaine on purinergic P2X3, P2X4, and P2X7 receptors to explore the mechanisms underlying pain-relieving effects of lidocaine. METHODS: We investigated the effects of lidocaine on ATP-induced currents in ATP receptor subunits, P2X3, P2X4, and P2X7 expressed in Xenopus oocytes, by using whole-cell, two-electrode, voltage-clamp techniques. RESULTS: Lidocaine inhibited ATP-induced currents in P2X7, but not in P2X3 or P2X4 subunits, in a concentration-dependent manner. The half maximal inhibitory concentration for lidocaine inhibition was 282 ± 45 µmol/L. By contrast, mepivacaine, ropivacaine, and bupivacaine exerted only limited effects on the P2X7 receptor. Lidocaine inhibited the ATP concentration-response curve for the P2X7 receptor via noncompetitive inhibition. Intracellular and extracellular N-(2,6-dimethylphenylcarbamoylmethyl) triethylammonium bromide (QX-314) and benzocaine suppressed ATP-induced currents in the P2X7 receptor in a concentration-dependent manner. In addition, repetitive ATP treatments at 5-minute intervals in the continuous presence of lidocaine revealed that lidocaine inhibition was use-dependent. Finally, the selective P2X7 receptor antagonists Brilliant Blue G and AZ11645373 did not affect the inhibitory actions of lidocaine on the P2X7 receptor. CONCLUSIONS: Lidocaine selectively inhibited the function of the P2X7 receptor expressed in Xenopus oocytes. This effect may be caused by acting on sites in the ion channel pore both extracellularly and intracellularly. These results help to understand the mechanisms underlying the analgesic effects of lidocaine when it is administered locally at least.

Synovial fluid bupivacaine concentrations following single intra-articular injection in normal and osteoarthritic canine stifles.

Intra-articular bupivacaine helps alleviate pain in animals receiving joint surgery, but its use has become controversial as ex vivo studies have illuminated the potential for chondrotoxicity. Such studies typically involve cell cultures incubated in solutions containing high bupivacaine concentrations for long durations. The aim of this study was to measure the actual synovial fluid bupivacaine concentrations after intra-articular injection. Eight healthy beagles with normal stifles and 22 large and giant-breed dogs with stifle osteoarthritis (OA) were treated with a single intra-articular injection of bupivacaine (1 mg/kg) into a stifle. Joint fluid samples were taken from the treated stifle immediately after injection and 30 min after injection and analyzed for bupivacaine concentrations. Immediately after injection, the median bupivacaine concentrations in normal and OA stifles were 3.6 and 2.5 mg/mL, respectively. Thirty minutes after injection, bupivacaine concentrations in normal and OA stifles were 0.4 and 0.6 mg/mL, respectively. These results provide insight into the pharmacokinetics of bupivacaine after injection into a joint. Given its immediate dilution and rapid drop in synovial fluid concentration, bupivacaine is unlikely to damage chondrocytes when administered as a single intra-articular injection.

Potential avoidance of adverse analgesic effects using a biologically "smart" hydrogel capable of controlled bupivacaine release.

Acute pain remains a tremendous clinical and economic burden, as its prevalence and common narcotic-based treatments are associated with poorer outcomes and higher costs. Multimodal analgesia portends great therapeutic promise, but rarely allows opioid sparing, and new alternatives are necessary. Microparticles (MPs) composed of biodegradable polymers [e.g., poly(lactic-co-glycolic acid) or PLGA] have been applied for controlled drug release and acute pain treatment research. However, foreign particles' presence within inflamed tissue may affect the drug release or targeting, and/or cause a secondary inflammatory reaction. We examined how small alterations in the particulate nature of MPs affect both their uptake into and subsequent activation of macrophages. MPs composed of PLGA and chitosan (PLGA-Chi) loaded with bupivacaine (BP) were engineered at different sizes and their opsonization by J774 macrophages was assessed. Uptake of PLGA-Chi by macrophages was found to be size dependent, but they were not cytotoxic or proinflammatory in effect. Moreover, encapsulation of MPs in a thermoresponsive loading gel (pluronic F-127) effectively prevented opsonization. Finally, MPs displayed sustained, tunable release of BP up to 7 days. These results demonstrate our ability to develop a drug delivery system capable of controlled release of local anesthetics to treat acute/subacute pain while concurrently avoiding enhanced inflammation.

Local anaesthetics: 10 essentials.

This review seeks to address 10 essential questions regarding the clinical use of local anaesthetics. Each local anaesthetic has distinctive physicochemical properties but with the same mode of action; they block voltage-gated sodium channels in the axon. Sodium channel block is brought about by a conformational change and the creation of a positive charge in the channel pore. Different local anaesthetics can reach the local anaesthetic binding site in the axon from the cytoplasmic compartment (classic hydrophilic pathway), or directly via its lipid membrane (hydrophobic pathway), or can enter via large-pore channels (alternative hydrophilic pathway). Beyond the nervous system, local anaesthetics exert beneficial effects on pain and can affect the inflammatory response and the haemostatic system. There are problems with the efficacy of local anaesthetics in the presence of local inflammation, and with significant intravascular toxicity, which can be fatal. But when preventive measures are taken, the incidence of cardiac arrest is low. Intralipid has been proposed to treat systemic local anaesthetic overdose and has been enthusiastically adopted worldwide, even though the mechanism of action is incompletely understood. Intralipid is an aid to the management of local anaesthetic toxicity rather than an antidote and meticulous conduct of regional anaesthesia remains paramount. All local anaesthetics are toxic, in a dose- and time-dependent manner, on virtually all tissues, including nerves and muscles. The question of whether local anaesthetics protect against perioperative tumour progression cannot be answered at this moment, and results from clinical (retrospective) studies are equivocal. Future areas of interest will be the design of new subtype-specific sodium channel blockers, but as we look forward, older local anaesthetics such as 2-chloroprocaine are being reintroduced into the clinical setting. Multimodal perineural analgesia and liposomal bupivacaine may replace catheter techniques for some indications.

Establishment of cytochrome P450 3A4 and glutathione S-transferase A1-transfected human hepatoma cell line and functional analysis.

This study aimed to enhance the drug metabolism function of the human hepatoma cell line C3A and to explore the related significance for patients with severe liver disease. The important liver phase I and phase II drug metabolism enzymes, cytochrome P450 3A4 (CYP 3A4) and glutathione S-transferase A1 (GST A1), were constructed into a double expression vector and then transfected into C3A cells. Furthermore, in order to increase the expression of CYP 3A4 and GST A1, they were optimized according to human optimal codons. Another double-expression vector, pBudCE4.1-optimized CYP 3A4-optimized GST A1, was constructed and then transfected into C3A to establish a stable cell line. The drug metabolism function of C3A was evaluated. Sequence determination and analysis results showed that the recombinant plasmid pBudCE4.1-CYP 3A4-GST A1 met the application standard and its transfection was successful. The expression and activity of CYP 3A4 and GST A1 in unoptimized C3A cells were higher than those in blank C3A cells. Unoptimized C3A had a better drug metabolism function. Although some C3A cells transfected with pBudCE4.1-optimized CYP 3A4-optimized GST A1 survived, they grew slowly, and were therefore not applicable in clinical practice. Unoptimized C3A is superior to blank C3A in drug metabolism, and could be applied in the bioartificial liver support system as a new material.