Extended release bupivacaine formulations for postoperative analgesia: an update

Comparison of bupivacaine liposome injectable solution and fentanyl for postoperative analgesia in dogs undergoing limb amputation

OBJECTIVE

The objectives of the study were to compare the clinical efficacy and adverse effects of two analgesic protocols consisting of bupivacaine liposome injectable solution (BLIS) and 0.5% bupivacaine and fentanyl for postsurgical analgesia in dogs undergoing limb amputation.

STUDY DESIGN

Randomized, double-blind, prospective, controlled, intent-to-treat, clinical noninferiority trial.

ANIMALS

Forty client-owned dogs.

METHODS

Dogs undergoing amputation were randomly assigned to either the BLIS or control group. Postoperative pain, sedation, nausea, and amount eaten were assessed using appropriate scales at 6, 12, 18, and 24 h by trained individuals blinded to the treatment protocol. Rescue analgesia was provided for Glasgow composite measure pain scale (short form) (CMPS-SF) scores of 5 or above. Clients were requested to pain score their dogs at home using a visual analogue scale (VAS) for 48 h following discharge.

RESULTS

Forty dogs completed this study (20 control dogs and 20 BLIS dogs). The BLIS and control groups were equivalent for sedation, nausea, amount eaten, and pain, at all time periods except at 6 h (p < .01), when the BLIS group pain score was lower.

CONCLUSION

The BLIS provided equivalent analgesia with fewer adverse effects than fentanyl constant rate infusion (CRI) following limb amputation. Rescue analgesia was provided to five dogs in the BLIS group and four in the control group, and there was no statistical difference. Nausea scores did not differ statistically.

CLINICAL SIGNIFICANCE

As BLIS provides equivalent analgesia, this may allow for decreased reliance on opioids in the immediate postoperative period.

Dose safety and pharmacodynamics of subcutaneous bupivacaine in a novel extended-release microparticle formulation: A phase 1, dose-ascending study in male volunteers

A novel microparticle-based extended-release local anaesthetic containing a bupivacaine/poly-lactic-co-glycolic acid (PLGA; LIQ865A) or plain bupivacaine (LIQ865B) was examined in a first-in-human trial. The objectives were to examine the dose safety/tolerability and pharmacodynamics. Randomized subcutaneous injections of LIQ865A (n = 16) or LIQ865B (n = 12) and diluent, contralaterally, were administered in a dose-ascending manner (150- to 600-mg bupivacaine). Subjects were admitted 24 h post-injection and followed for 30 days post-injection. The risk ratios (RRs; 95% CI) of erythematous reactions for LIQ865A versus diluent was 9.00 (1.81-52.23; P = 0.006) and for LIQ865B versus diluent 2.50 (0.69-9.94; P = 0.37). The RR for the development of hematomas (LIQ865A versus diluent) were 3.25 (1.52-8.16; P = 0.004) and 4.00 (0.72-24.89; P = 0.32) (LIQ865B versus diluent). Subcutaneous indurations persisting for 4-13 weeks were seen in 6/16 subjects receiving LIQ865A. One subject receiving LIQ865A (600-mg bupivacaine) developed intermittent central nervous system (CNS) symptoms of local anaesthetic systemic toxicity (85 min to 51 h post-injection) coinciding with plasma peak bupivacaine concentrations (490-533 ng/ml). Both LIQ865 formulations demonstrated dose-dependent hypoesthesia and hypoalgesia. The duration of analgesia ranged between 37 and 86 h. The overall number of local adverse events, however, prohibits clinical application without further pharmacological modifications.

Population pharmacokinetic-pharmacodynamic model of subcutaneous bupivacaine in a novel extended-release microparticle formulation

The objective of this study was to develop a population pharmacokinetic-pharmacodynamic model of subcutaneously administered bupivacaine in a novel extended-release microparticle formulation for postoperative pain management. Bupivacaine was administered subcutaneously in the lower leg to 28 healthy male subjects in doses from 150 to 600 mg in a phase 1 randomized, placebo-controlled, double-blind, dose-ascending study with two different microparticle formulations, LIQ865A and LIQ865B. Warmth detection threshold was used as a surrogate pharmacodynamic endpoint. Population pharmacokinetic-pharmacodynamic models were fitted to plasma concentration-effect-time data using non-linear mixed-effects modelling. The pharmacokinetics were best described by a two-compartment model with biphasic absorption as two parallel absorption processes: a fast, zero-order process and a slower, first-order process with two transit compartments. The slow absorption process was found to be dose-dependent and rate-limiting for elimination at higher doses. Apparent bupivacaine clearance and the transit rate constant describing the slow absorption process both appeared to decrease with increasing doses following a power function with a shared covariate effect. The pharmacokinetic-pharmacodynamic relationship between plasma concentrations and effect was best described by a linear function. This model gives new insight into the pharmacokinetics and pharmacodynamics of microparticle formulations of bupivacaine and the biphasic absorption seen for several local anaesthetics.

Reduced Opioid Use Among Patients Who Received Liposomal Bupivacaine Brachial Plexus Block for Total Shoulder Arthroplasty

Purpose This retrospective cohort explores the efficacy of regional shoulder blocks using Exparel™ in patients undergoing total shoulder arthroplasty (TSA)/reverse total shoulder arthroplasty (RSA) to reduce total opioid prescription, refills, and length of stay in the acute care setting. Methods Patients who underwent TSA/RSA by a single surgeon in a three-year period were evaluated. Patients in the case group received liposomal bupivacaine 1.3% brachial plexus block while the control group received ropivacaine 0.5% interscalene brachial plexus block. Outcomes of the study included the number of opioids taken, opioids prescribed, and length of hospital stay. Results Thirty-six patients underwent TSA/RSA between January 2017 and March 2020. Patients who received an Exparel brachial plexus block had decreased opioid use within the first 24 hours after surgery compared to the ropivacaine group, 9.00 ± 14.10 and 26.20 ± 24.8 morphine milligram equivalent (MME), respectively (p=0.0213). Patients who received an Exparel brachial plexus block had decreased opioid prescriptions over the entire postoperative follow-up, 411.00 ± 200.74 MME in the case group and 593.07 ± 297.57 MME in the control group (p=0.0314). Lastly, patients who received an Exparel brachial plexus block had a shorter length of hospital stay, 1.28 ± 0.91 days as compared to the control group's 2.15 ± 1.49 days (p=0.0451). Conclusion This study demonstrates a significant reduction in opioid prescribing and use in patients who receive Exparel brachial plexus nerve blocks compared to non-liposomal local anesthetics, as well as a significant reduction in the length of hospital stay. The data suggest that Exparel use may decrease the risks associated with opioid use while providing adequate analgesia in patients undergoing shoulder arthroplasty.

Single-shot liposomal bupivacaine in place of rectus sheath catheters to provide non-opiate analgesia after laparotomy: a quality improvement project to reduce the need for ongoing nursing input

Opioid-sparing pain management is an integral component of enhanced recovery after colonic and rectal surgery. In our hospital, rectus sheath catheters (RSCs) are routinely placed during emergency laparotomy for colorectal procedures to allow a postoperative compartmental block of the surgical site with repeated doses of bupivacaine. However, RSCs require a significant amount of clinical nursing time to maintain and 'top-up'. We present a quality improvement project in which we administered single-shot liposomal bupivacaine (LB) intraoperatively as an alternative to bolus doses of conventional bupivacaine delivered through RSCs. Having thereby reduced the demands placed on nursing time through a reduction in the use of RSCs, we sought to establish whether there was any associated change in analgesic efficacy. Patient pain scores, use of patient-controlled analgesia (PCA) and length of stay following surgery were analysed before and after the introduction of LB. No disruption in these outcomes was identified using statistical process control analysis. A direct comparison of results for patients who received LB versus those who received bolus dosing of bupivacaine via RSCs found no significant differences, with a median total PCA dose of 270 mg oral morphine equivalents (OME) for patients who received LB versus 396 mg OME for patients who had RSCs (p=0.54). The median length of stay for patients who received LB was 15.5 days versus 16 days for those who had RSCs (p=0.87). We conclude that LB represents a viable alternative to boluses of conventional bupivacaine via RSCs in promoting enhanced recovery after emergency laparotomy and look to extend its use locally.

Nanocrystals Slow-Releasing Ropivacaine and Doxorubicin to Synergistically Suppress Tumor Recurrence and Relieve Postoperative Pain

Although surgical resection provides a straightforward and effective treatment for most malignant solid tumors, tumor recurrence and acute postoperative pain continue to be two big problems associated with this treatment. To resolve these problems, a nanocrystal composite slow-releasing ropivacaine and doxorubicin was fabricated in this study. Briefly, a self-assembling peptide was used to form nanoparticle complexes with the two drugs, based on which homogeneous nanocrystals were obtained by adjusting the pH. In cultured human melanoma cells, the nanocrystals exhibited improved antitumor activity due to a synergistic effect and enhanced cellular uptake of the two drugs. On the other hand, the nanocrystals could slowly release ropivacaine in vitro and in vivo, generating long-acting analgesia on the rat sciatic nerve block model and incisional pain model. On a nude mouse tumor resection model, the nanocrystals simultaneously suppressed the recurrence of solid tumor and relieved postoperative pain, indicating a potential postoperative treatment for tumor resection patients. This nanocrystal system also suggested a promising and facile strategy for developing multifunctional formulations combining different drugs, which could achieve better therapeutic outcomes in a synergistic and sustained manner.

Sustained release of levobupivacaine from temperature-sensitive injectable hydrogel for long-term local anesthesia in postoperative pain management

Postoperative pain is a major concern for most of the surgical patients, and an inadequate postoperative pain control may cause a series of complications. With an effective pain control and lesser side effects, local anesthetics are preferred for use in postoperative pain management. However, the action duration of current local anesthetics is too short to meet the requirements of postoperative analgesia. In this study, an injectable levobupivacaine (LB)-loaded thermo-sensitive hydrogel system based on biodegradable poly(D,L-lactide)-poly(ethylene glycol)-poly(D,L-lactide) (PLEL) was developed for long-acting local anesthetic, in which the soluble charged cation form of LB (LB HCl) was partly alkalified to the poorly soluble base form (LB base). This hybrid LB loaded PLEL system (hLB/PLEL) is a free flowable liquid at room temperature and changes into a semi-solid hydrogel once injection in response to the physiological temperature. Then, the dissolved LB HCl could release firstly from the hydrogel contributing to a quick work, and the insoluble LB base dissolved and released gradually as the decrease of the pH during the biodegradation of PLEL hydrogel, resulting in a long-term LB release in local. The drug release behavior, pharmacokinetic, and biocompatibility of the thermo-sensitive hLB/PLEL were studied in vitro and in vivo. The anesthetic effects of hLB/PLEL system were evaluated in the rat models of sciatic nerve block, subcutaneous infiltration anesthesia and postoperative pain as well. This hLB/PLEL system generated a significantly prolonged analgesic effect in rat models, which produced approximately 7 times longer duration than 0.75% LB HCl and effectively relieved the spontaneous pain for 3 days. In general, the presented hLB/PLEL system can not only achieve a fast-acting but also sustainably release LB to block the nerve and significantly extend the effect of local analgesia, which means a promising candidate for long-acting postoperative pain management.

Peripheral Regional Anesthesia Using Local Anesthetics: Old Wine in New Bottles?

During the past decade, numerous efforts were undertaken aiming at prolonging the analgesic effect of regional anesthesia. With the development of extended-release formulations and enhanced selectivity for nociceptive sensory neurons, a very promising contribution to the development of pain medications has been achieved. At present, liposomal bupivacaine is the most popular, non-opioid, controlled drug delivery system, but its duration of action, which is still controversially discussed, and its expensiveness have decreased initial enthusiasm. Continuous techniques can be seen as an elegant alternative for providing a prolonged duration of analgesia, but for logistic or anatomical reasons, they are not always the best choice. Therefore, focus has been directed towards the perineural and/or intravenous addition of old and established substances. As for perineural application, most of these so-called 'adjuvants' are used outside their indication, and their pharmacological efficacy is often not or only poorly understood. This review aims to summarize the recent developments for prolonging the duration of regional anesthesia. It will also discuss the potential harmful interactions and side effects of frequently used analgesic mixtures.

Measures to prolong duration of sensory block after regional anaesthesia

PURPOSE OF REVIEW

The duration of single-injection regional anaesthesia is limited due to the inherent pharmacological properties of local anaesthetics. The ideal duration of a regional anaesthesia block lasting for the first 24 h postoperatively can be stated, while a residual analgesic effect thereafter is desirable.The aim of this review is to present current options to prolong the duration of action of single-injection peripheral regional anaesthesia in the ambulatory setting. Secondly, this review outlines and discusses the latest evidence regarding the clinical use of adjuvants and sustained-release local anaesthetics.

RECENT FINDINGS

Extended-release formulations of local anaesthetics such as liposomal bupivacaine have been developed to prolong regional anaesthesia up to 96 h. Recent studies, however, show that the actual effects remain far behind expectations and that the efficacy is only marginally better than bupivacaine hydrochloride.Adjuvants to local anaesthetics have been studied extensively with heterogenous results. Dexamethasone and alpha-2 agonists range among the most effective measures to prolong single-injection nerve blocks.Continuous nerve blocks and catheter techniques may prolong regional anaesthesia very effectively, but are less cost-effective regarding block procedure, postoperative care and handling logistical issues especially in ambulatory surgery.

SUMMARY

In conclusion, adjuvants are the recommended measure to prolong regional anaesthesia where needed. With good evidence supporting it, dexamethasone is the most effective adjuvant, followed by dexmedetomidine. Both have few side effects and a favourable safety profile. However, a preferable duration of analgesia lasting for the first 24 h postoperatively is still not reliably achievable.

Combination anesthetic therapy: co-delivery of ropivacaine and meloxicam using transcriptional transactivator peptide modified nanostructured lipid carriers in vitro and in vivo

Combination therapy combining two drugs in one modified drug delivery system is used to achieve synergistic analgesic effect, and bring effective control of pain management, especially postoperative pain management. In the present study, a combination of drug delivery technologies was utilized. Transcriptional transactivator (TAT) peptide modified, transdermal nanocarriers were designed to co-deliver ropivacaine (RVC) and meloxicam (MLX) and anticipated to achieve longer analgesic effect and lower side effect. TAT modified nanostructured lipid carriers (TAT-NLCs) were used to co-deliver RVC and MLX. RVC and MLX co-loaded TAT-NLCs (TAT-NLCs-RVC/MLX) were evaluated through in vitro skin permeation and in vivo treatment studies. NLCs-RVC/MLX showed uniform and spherical morphology, with a size of 133.4 ± 4.6 nm and a zeta potential of 20.6 ± 1.8 mV. The results illustrated the anesthetic pain relief ability of the present constructed system was significantly improved by the TAT modification through the enhanced skin permeation efficiency and the co-delivery of MLX along with RVC that improved pain management by reducing inflammation at the injured area. This study provides an efficient and facile method for preparing TAT-NLCs-RVC/MLX as a promising system to achieve synergistic analgesic effect.

Development and in vivo validation of phospholipid-based depots for the sustained release of bupivacaine

By direct deposition of the drug at the local site of action, injectable depot formulations - intended for treatment of a local disease or for local intervention - are designed to limit the immediate exposure of the active principle at a systemic level and to reduce the frequency of administration. To overcome known drawbacks in the production of some marketed phospholipid-based depots, here we propose to manufacture drug-loaded negatively charged liposomes through conventional technologies and to control their aggregation mixing a solution of divalent cations prior to administration. We identified phosphatidylglycerol (PG) as the most suitable phospholipid for controlled aggregation of the liposomes and to modulate the release of the anesthetic bupivacaine (BUP) from liposomal depots. In vivo imaging of the fluorescently-labelled liposomes showed a significantly higher retention of the PG liposomes at the injection site with respect to zwitterionic ones. In situ mixing of PG liposomes with calcium salts significantly extended the area under the curve of BUP in plasma compared to the non-depot system. Overall, controlling the aggregation of negatively charged liposomes with divalent cations not only modulated the particle clearance from the injection site but also the release in vivo of a small amphipathic drug such as BUP.

Epidural bupivacaine administration after infiltration of liposomal bupivacaine for transversalis fascia plane block: A case report

Extended-release liposomal bupivacaine is frequently used in surgical infiltration for postoperative pain control. The manufacturer recommends against subsequent local anesthetics within 96 hours. We administered epidural bupivacaine one day after local liposomal bupivacaine infiltration for staged hemipelvectomy without symptoms of LAST. Further pharmacokinetic and clinical safety studies are needed.

Use of Opioids in the Early Postoperative Period After Arthroscopic Rotator Cuff Repair: A Systematic Review

Background:

Postoperative treatment plans after orthopaedic procedures frequently include opioids for pain relief.

Purpose:

To evaluate opioid use in the early postoperative phase after arthroscopic rotator cuff repair (ARCR) to develop a procedure-specific understanding of the current role of opioids in pain management for this procedure.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A PubMed search was used to identify eligible studies. Data on patient demographics, visual analog scale pain scores, and opioid use patterns (in morphine milligram equivalents [MMEs]) were collected and assessed. Cumulative MMEs were reported on postoperative day (POD) zero, and mean MMEs were reported on subsequent PODs (days 1, 2, 3, 5, 7, and 14). Metaregression, I² indices, and Cochran Q tests were used to evaluate study variation, heterogeneity, and variance.

Results:

A total of 1487 patients in 22 studies were included in the analysis. An estimated 51% (95% CI, 31%-70%) of patients with nerve blocks (NBs) were opioid-free through POD-0 versus 40% (95% CI, 1.2%-97%) of patients without NBs, which increased to 65% (95% CI, 55%-74%) versus 25% (95% CI, 1.7%-86%) by POD-1. Opioid requirements were highest in the first 72 hours after ARCR. NB use reduced opioid requirement on POD-0 compared with no NB use (15.8 vs 45.0 MMEs, respectively; P < .001) but did not reduce requirements after that. In addition, NB use led to a statistically significant increase in opioid requirements on POD-7 (28.6 vs 9.5 MMEs, respectively; P < .001). Using a model that assumes stable opioid requirements between our time points, weighted mean cumulative opioid consumption was 163 MMEs in the first week and 273 MMEs in the first 2 weeks (150 and 287 MMEs in patients with NB; 180 and 261 MMEs in patients without NB, respectively).

Conclusion:

Opioid use is relatively common in the early postoperative period after ARCR. Pain scores and opioid requirements may spike on POD-1; however, patients should be educated and reassured that they will gradually decrease usage over the initial 2-week postoperative period.

[Liposomal bupivacaine-No breakthrough in postoperative pain management]

One of the main limitations concerning the use of local anesthetics is due to their restricted duration of action. In recent years, liposomal formulations with prolonged release kinetics have been developed to extend the pharmacological duration of action of the 1‑stage peripheral regional anesthesia (single-shot procedure) and thus bring about a longer duration of action. The focus here is particularly on achieving postoperative freedom from pain for at least 24 h (or even better 48 h) and thus early mobilization of patients using on-demand medication causing (at most) minor local sensory blockade without causing motor impairments (at least that is the ideal). Therefore, methods of utilizing slow-release drugs as seen in liposomal carrier systems have experienced increasing scientific attention in the last few years. A common modern pharmacological example with a theoretically significantly longer duration of action is liposomal bupivacaine, an amide local anesthetic. Due to a multivesicular liposome structure, the retarded release of the active component bupivacaine HCl leads to a theoretical pharmacological effectiveness of up to 72 h. Previous studies consistently showed a safety profile comparable to conventional bupivacaine HCl. Liposomal bupivacaine has been approved by the U.S. Food and Drug Administration (FDA) under the trade name Exparel© (Pacira Pharmaceuticals, Parsippany, NJ, USA) since 2011; however, its use is currently limited to local wound infiltration, transverse abdominis plane (TAP) blocks, and interscalene nerve blocks of the brachial plexus. In 2020, the European Medicines Agency (EMA) also approved the use of liposomal bupivacaine for blockade of the brachial plexus or the femoral nerve and as a field block or for wound infiltration to treat postoperative pain. So far, studies on the clinical effectiveness of liposomal bupivacaine have been very heterogeneous and there have been no conclusive meta-analyses with sufficient rigor or significance. Recent systematic reviews and meta-analyses, combining the results of clinical studies regarding the analgesic efficiency of liposomal bupivacaine in different fields of application, consistently refuted any benefit of clinical relevance provided by the liposomal formulation. There is currently sufficient evidence to now end the ongoing debate around liposomal bupivacaine. The aim of this work is to give the reader a current, evidence-based overview of this substance.

Interscalene Brachial Plexus Block with Liposomal Bupivacaine versus Standard Bupivacaine with Perineural Dexamethasone: A Noninferiority Trial

BACKGROUND

The interscalene nerve block provides analgesia for shoulder surgery. To extend block duration, provide adequate analgesia, and minimize opioid consumption, the use of adjuvants such as dexamethasone as well as the application of perineural liposomal bupivacaine have been proposed. This randomized, double-blinded, noninferiority trial hypothesized that perineural liposomal bupivacaine is noninferior to standard bupivacaine with perineural dexamethasone in respect to average pain scores in the first 72 h after surgery.

METHODS

A total of 112 patients undergoing ambulatory shoulder surgery were randomized into two groups. The liposomal bupivacaine group received a 15-ml premixed admixture of 10 ml of 133 mg liposomal bupivacaine and 5 ml of 0.5% bupivacaine (n = 55), while the bupivacaine with dexamethasone group received an admixture of 15 ml of 0.5% standard bupivacaine with 4 mg dexamethasone (n = 56), respectively. The primary outcome was the average numerical rating scale pain scores at rest over 72 h. The mean difference between the two groups was compared against a noninferiority margin of 1.3. Secondary outcomes were analgesic block duration, motor and sensory resolution, opioid consumption, numerical rating scale pain scores at rest and movement on postoperative days 1 to 4 and again on postoperative day 7, patient satisfaction, readiness for postanesthesia care unit discharge, and adverse events.

RESULTS

A liposomal bupivacaine group average numerical rating scale pain score over 72 h was not inferior to the bupivacaine with dexamethasone group (mean [SD], 2.4 [1.9] vs. 3.4 [1.9]; mean difference [95% CI], -1.1 [-1.8, -0.4]; P < 0.001 for noninferiority). There was no significant difference in duration of analgesia between the groups (26 [20, 42] h vs. 27 [20, 39] h; P = 0.851). Motor and sensory resolutions were similar in both groups: 27 (21, 48) h versus 27 (19, 40) h (P = 0.436) and 27 [21, 44] h versus 31 (20, 42) h (P = 0.862), respectively. There was no difference in opioid consumption, readiness for postanesthesia care unit discharge, or adverse events.

CONCLUSIONS

Interscalene nerve blocks with perineural liposomal bupivacaine provided effective analgesia similar to the perineural standard bupivacaine with dexamethasone. The results show that bupivacaine with dexamethasone can be used interchangeably with liposomal bupivacaine for analgesia after shoulder surgery.

EDITOR’S PERSPECTIVE

Bupivacaine for Root Canal Treatment – Practitioner Behaviors and Patient Perspectives: Survey Studies

Introduction and Objectives

Local anesthesia is essential in dentistry in providing intraoperative analgesia and anesthesia. However, knowledge related to its use for management of post-operative pain is limited. Perioperative pain management is especially important for root canal treatment (ie, endodontic therapy), performed by endodontists. In this study, we sought to better understand endodontists’ attitudes regarding the use of long-lasting anesthetic, namely 0.5% bupivacaine HCl with 1:200,000 epinephrine, for the management of post-endodontic pain. Additionally, we aimed to understand the perspectives of dental patients about receiving longer lasting anesthesia for endodontic therapy and to determine factors that affect their anesthetic preferences within the orofacial region.

Methods

An email invitation to participate in an anonymous online survey was sent to members of the American Association of Endodontists. Also, 82 patients attending an in-person visit to an endodontic clinic were recruited to the study.

Results

Data from 474 endodontic practitioners and 82 patients included in analysis. Among practitioners, the majority reported to either never (33.31%) or rarely (34.84%) using bupivacaine. Most chose “I don’t think I need it” (47%) and “patient discomfort because of longer duration of soft tissue anesthesia” (30.81%) as reasons for not preferring the use of bupivacaine. Of the practitioners who reported at least rare use, most chose bupivacaine for post-operative pain management (78.02%). Conversely, 52% of patients reported that they were likely/most likely to request long-lasting anesthetics for post-operative pain control.

Conclusion

Bupivacaine is rarely used as a post-operative pain management strategy for endodontic therapy. Specifically, bupivacaine is not preferred not because of adverse events, toxicity, or slow onset concerns, but rather, because of longer duration of soft tissue anesthesia. However, our data suggest that patients may be willing to receive long-lasting anesthesia. Further patient-centered research should investigate the use of long-lasting anesthetic agents for management of post-endodontic pain.

Emerging drugs for the treatment of postsurgical pain

INTRODUCTION

Postoperative pain is a distressful experience and remains to be a significant concern after surgery. Current agents either fail to prevent or minimize postoperative pain or cause a series of adverse effects, addiction, or abuse. Opioids have been the gold standard in the treatment of postoperative pain despite their well-described adverse effects. Many new agents with different mechanisms of action have been recently introduced to address this issue.

AREAS COVERED

This current review summarizes the list of new and emerging drugs investigated for their efficacy in controlling the postoperative pain and decreasing the need for rescue opioid use, adverse effect profile, abuse, and addiction potential.

EXPERT OPINION

Opioids have unrivaled analgesic efficacy. However adverse effects of opioids led to the search for better options. In mild pain most of the emerging drugs have been shown to control postoperative pain and decrease the use of rescue opioid, however fail to control pain after major surgeries causing severe pain. Specific agents such as Oliceridine, new local anesthetics, etc., are effective in controlling severe pain and hold a promise to replace opioids in the near future.

Bupivacaine liposome use reduces length of post-anesthesia care unit stay and postoperative narcotic use following robotic inguinal herniorrhaphy

In the current opioid crisis, multimodal analgesic protocols should be considered to reduce or eliminate narcotic usage in the postoperative period. We assess the impact of bupivacaine liposome used along with a standard analgesia protocol following robotic inguinal hernia repair. A retrospective review of a prospectively maintained data including robotic inguinal hernia repairs (IHR) by two surgeons in the United States was performed. Within a multimodal analgesic protocol, local anesthetic was administered intraoperatively. One group received a mix of bupivacaine and bupivacaine liposome (BL), and one received standard bupivacaine (SB). Recovery room and home opiate doses were recorded. Primary outcomes included length of stay (LOS) and postoperative medication requirements. Statistical analysis was performed using Chi-square or Fisher's exact test and Mann-Whitney U test as appropriate. 122 robotic IHRs were included; 55 received BL and 67 received SB. Hospital LOS (hours) was reduced in the BL group (2.8 ± 1.1 vs 3.5 ± 1.2; p = 0.0003). There was no significant difference in recovery room parenteral MME requirements between the groups; however, BL group had less oral MME requirements (5.0 ± 6.5 MME vs. 8.1 ± 6.9 MME, p = 0.02). The BL group had a higher rate of zero opiate doses at home (44% vs 5%, p = 0.0005). Of those that did require opiates at home, there was a significant reduction in number of narcotic pills used by the BL compared to the SB group (median 1 vs 5, respectively; p < 0.0001). Intraoperative administration of BL as part of a pain management protocol may decrease length of hospital stay, and reduce or eliminate the need for narcotic analgesic use at home.

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.

HTX-011 effectively reduces postoperative pain intensity and opioid use in the elderly

Aim: HTX-011 (ZYNRELEF™) is an extended-release, dual-acting local anesthetic containing bupivacaine and meloxicam. In bunionectomy and herniorrhaphy studies, HTX-011 resulted in less postoperative pain and less opioid consumption versus bupivacaine HCl. Here we evaluate HTX-011 in patients aged ≥65 years. Materials & methods: Patients received placebo, bupivacaine HCl or HTX-011 following surgery. End points included pain intensity, total opioid consumption, opioid-free patients and safety. Results: HTX-011-treated patients reported lower postoperative pain through 72 h versus bupivacaine HCl and placebo. Elderly patients administered HTX-011 used fewer opioids versus bupivacaine HCl, and a greater proportion remained opioid-free through 72 h. HTX-011 was well tolerated with a safety profile similar to bupivacaine HCl and placebo. Conclusion: HTX-011 maintained effectiveness and was well tolerated in elderly patients. Clinical Trial Registration: NCT03295721 and NCT03237481.

Evaluation of Liposomal Bupivacaine at Split Thickness Skin Graft Donor Sites Through a Randomized, Controlled Trial

Split thickness skin grafts (STSG) are commonly required in reconstructive surgery but may cause significant pain. The goal of this investigator-initiated trial is to evaluate the effect of liposomal bupivacaine on donor site pain and opioid consumption. A parallel, randomized, controlled trial of adult acute burn patients with <20% total body surface area burns (TBSA) was conducted to evaluate the efficacy of liposomal bupivacaine at STSG donor sites. The control group received standard subcutaneous infiltration of dilute lidocaine solution at the STSG donor site, and the experimental group received dilute liposomal bupivacaine infiltration in a similar fashion. Donor site pain scores and opioid consumption in morphine equivalents (MEE) were evaluated. A total of 25 patients were enrolled in each group. There were no statistical differences in demographic variables, and TBSA was 4.0% in both groups (p=.94). There were no statistical differences in pain scores at any time point postoperatively (mean control range 3.1/10-4.9/10, experimental range 3.3/10-4.3/10, p=.12-.96). There were no statistical differences in opioid consumption at 24, 48, or 72 hours postoperatively between the groups (mean control MEE range 49.3-71.1, experimental MEE range 63.6-75.8, p=.34-.85). The average length of stay was 7.7 days in both groups (p=.88). No adverse events occurred in either group. There is no statistical benefit to the use of liposomal bupivacaine for infiltration at STSG donor sites compared to standard of care with respect to pain control, opioid use, or length of stay when evaluated in a randomized, controlled fashion.

Liposomal bupivacaine infiltration in the surgical site for analgesia after rotator cuff repair: a randomized, double-blinded, placebo-controlled trial

INTRODUCTION

Arthroscopic rotator cuff repair is among the most painful of orthopedic surgeries. Liposomal bupivacaine is Food and Drug Administration approved for administration into surgical sites to provide postsurgical analgesia and has been used to address postoperative pain after many types of surgery, including total shoulder arthroplasty. However, its efficacy for pain control after rotator cuff repair is unclear.

METHODS

In this randomized, double-blind, placebo-controlled trial, we compared liposomal bupivacaine with an equivalent volume of saline injected into the subacromial space and arthroscopy portal sites in patients undergoing rotator cuff repair under the interscalene block with sedation. The primary outcome measure was numeric rating pain score at the time of block resolution, as reported during the follow-up phone call on postoperative day 1. Secondary outcomes included mean pain scores at rest as well as oral morphine equivalent requirements on postoperative days 1, 2, and 3. This study provides Level 1 evidence.

RESULTS

There were no statistically significant differences in the primary outcome of numeric rating pain scores on resolution of the interscalene nerve block, nor in those reported on postoperative day 1 or 2. There was a minor but statistically significant difference in mean resting pain scores on day 3, though opioid consumption and patient satisfaction score did not differ between groups. In those instructed to perform passive range-of-motion exercises, there was no difference in reported mean pain scores among the groups.

DISCUSSION

In this study of patients undergoing arthroscopic rotator cuff repair, we found no statistically significant difference in mean pain scores on interscalene block resolution, a result consistent with a number of studies investigating liposomal bupivacaine for total shoulder arthroplasty. A modest reduction in pain was evident only on day 3, and there was no impact on perioperative opioid requirements, opioid-related side effects, or pain with motion. Liposomal bupivacaine, when injected into the subacromial space and the tissues around the arthroscopy port sites, provided minimal improvement in pain control in this patient population.

The analgesic efficacy of liposomal bupivacaine compared with bupivacaine hydrochloride for the prevention of postoperative pain: a systematic review and meta-analysis with trial sequential analysis

BACKGROUND/IMPORTANCE

Liposomal bupivacaine (LB) is a prolonged release formulation of conventional bupivacaine designed for prolonging local or peripheral regional single injection anesthesia. To this day, the benefit of the new substance on relevant end points is discussed controversial.

OBJECTIVE

The objective was to determine whether there is a difference in postoperative pain scores and morphine consumption between patients treated with LB and bupivacaine hydrochloride in a systematic review and meta-analysis.

EVIDENCE REVIEW

Randomized controlled trials (RCT) were identified in Embase, CENTRAL, MEDLINE and Web of Science up to May 2020. Risk of bias was assessed using Cochrane methodology. Primary end points were the mean pain score difference and the relative morphine equivalent (MEQ) consumption expressed as the ratio of means (ROM) 24 and 72 hours postoperatively.

FINDINGS

23 RCTs including 1867 patients were eligible for meta-analysis. The mean pain score difference at 24 hours postoperatively was significantly lower in the LB group, at -0.37 (95% CI -0.56 to -0.19). The relative MEQ consumption after 24 hours was also significantly lower in the LB group, at 0.85 (0.82 to 0.89). At 72 hours, the pain score difference was not significant at -0.25 (-0.71 to 0.20) and the MEQ ratio was 0.85 (0.77 to 0.95).

CONCLUSION

The beneficial effect on pain scores and opioid consumption was small but not clinically relevant, despite statistical significance. The effect was stable among all studies, indicating that it is independent of the application modality.

Low concentration of Bupivacaine ameliorates painful diabetic neuropathy by mediating miR-23a/PDE4B axis in microglia

Bupivacaine (Bup) has a certain research basis in pain-related diseases, but it has not been studied in painful diabetic neuropathy. In this study, we investigated the role of Bupivacaine in painful diabetic neuropathy. Mouse model with painful diabetic neuropathy was established, and then treated with different concentrations of Bupivacaine. The blood glucose level in the tail vein and the changes in body weight was measured. The mechanical allodynia, thermal hyperalgesia and thermal allodynia was assessed by pain behavioral tests. Microglia were treated with high glucose (HG) and different concentrations of Bupivacaine. The levels of inflammatory cytokines were detected by using Enzyme-linked immunosorbent assays. Dual luciferase reporter assay explored the relationship between miR-23a and phosphodiesterase 4 B (PDE4B). The results displayed that Bupivacaine ameliorated the mechanical allodynia, thermal hyperalgesia, and thermal allodynia in mice with painful diabetic neuropathy, and is more effective at low concentration. Moreover, low concentration of Bupivacaine inhibited inflammation and promoted miR-23a expression in mice with painful diabetic neuropathy and in microglia induced by HIGH GLUCOSE. Overexpression of miR-23a reduced the levels of inflammatory cytokines by down-regulating PDE4B expression. Knockdown of miR-23a reversed the inhibition effect of Bupivacaine on microglial inflammation. These results revealed that low concentration of Bupivacaine inhibited microglial inflammation through down-regulating PDE4B via miR-23a, thereby attenuated painful diabetic neuropathy.

Procedure-specific and patient-specific pain management for ambulatory surgery with emphasis on the opioid crisis

PURPOSE OF REVIEW

Postoperative pain is frequent while, on the other hand, there is a grooving general concern on using effective opioid pain killers in view of the opioid crisis and significant incidence of opioid abuse. The present review aims at describing nonopioid measures in order to optimize and tailor perioperative pain management in ambulatory surgery.

RECENT FINDINGS

Postoperative pain should be addressed both preoperatively, intraoperatively and postoperatively. The management should basically be multimodal, nonopioid and procedure-specific. Opioids should only be used when needed on top of multimodal nonopioid prophylaxis, and then limited to a few days at maximum, unless strict control is applied. The individual patient should be screened preoperatively for any risk factors for severe postoperative pain and/or any abuse potential.

SUMMARY

Basic multimodal analgesia should start preoperatively or peroperatively and include paracetamol, cyclo-oxygenase (COX)-2 specific inhibitor or conventional nonsteroidal anti-inflammatory drug (NSAID) and in most cases dexamethasone and local anaesthetic wound infiltration. If any of these basic analgesics are contraindicated or there is an extra risk of severe postoperative pain, further measures may be considered: nerve-blocks or interfascial plane blocks, gabapentinnoids, clonidine, intravenous lidocaine infusion or ketamine infusion. In the abuse-prone patient, a preferably nonopioid perioperative approach should be aimed at.

Intracellular G-actin targeting of peripheral sensory neurons by the multifunctional engineered protein C2C confers relief from inflammatory pain

The engineered multifunctional protein C2C was tested for control of sensory neuron activity by targeted G-actin modification. C2C consists of the heptameric oligomer, C2II-CI, and the monomeric ribosylase, C2I. C2C treatment of sensory neurons and SH-SY5Y cells in vitro remodeled actin and reduced calcium influx in a reversible manner. C2C prepared using fluorescently labeled C2I showed selective in vitro C2I delivery to primary sensory neurons but not motor neurons. Delivery was dependent on presence of both C2C subunits and blocked by receptor competition. Immunohistochemistry of mice treated subcutaneously with C2C showed colocalization of subunit C2I with CGRP-positive sensory neurons and fibers but not with ChAT-positive motor neurons and fibers. The significance of sensory neuron targeting was pursued subsequently by testing C2C activity in the formalin inflammatory mouse pain model. Subcutaneous C2C administration reduced pain-like behaviors by 90% relative to untreated controls 6 h post treatment and similarly to the opioid buprenorphene. C2C effects were dose dependent, equally potent in female and male animals and did not change gross motor function. One dose was effective in 2 h and lasted 1 week. Administration of C2I without C2II-CI did not reduce pain-like behavior indicating its intracellular delivery was required for behavioral effect.

Neurotoxicity of bupivacaine and liposome bupivacaine after sciatic nerve block in healthy and streptozotocin-induced diabetic mice

Background

Long-acting local anaesthetics (e.g. bupivacaine hydrochloride) or sustained-release formulations of bupivacaine (e.g. liposomal bupivacaine) may be neurotoxic when applied in the setting of diabetic neuropathy. The aim of the study was to assess neurotoxicity of bupivacaine and liposome bupivacaine in streptozotocin (STZ) - induced diabetic mice after sciatic nerve block. We used the reduction in fibre density and decreased myelination assessed by G-ratio (defined as axon diameter divided by large fibre diameter) as indicators of local anaesthetic neurotoxicity.

Results

Diabetic mice had higher plasma levels of glucose (P < 0.001) and significant differences in the tail flick and plantar test thermal latencies compared to healthy controls (P < 0.001). In both diabetic and nondiabetic mice, sciatic nerve block with 0.25% bupivacaine HCl resulted in a significantly greater G-ratio and an axon diameter compared to nerves treated with 1.3% liposome bupivacaine or saline (0.9% sodium chloride) (P < 0.01). Moreover, sciatic nerve block with 0.25% bupivacaine HCl resulted in lower fibre density and higher large fibre and axon diameters compared to the control (untreated) sciatic nerves in both STZ-induced diabetic (P < 0.05) and nondiabetic mice (P < 0.01). No evidence of acute or chronic inflammation was observed in any of the treatment groups.

Conclusions

In our exploratory study the sciatic nerve block with bupivacaine HCl (7 mg/kg), but not liposome bupivacaine (35 mg/kg) or saline, resulted in histomorphometric indices of neurotoxicity. Histologic findings were similar in diabetic and healthy control mice.

CaproGlu: Multifunctional tissue adhesive platform

Driven by the clinical need for a strong tissue adhesive with elastomeric material properties, a departure from legacy crosslinking chemistries was sought as a multipurpose platform for tissue mending. A fresh approach to bonding wet substrates has yielded a synthetic biomaterial that overcomes the drawbacks of free-radical and nature-inspired bioadhesives. A food-grade liquid polycaprolactone grafted with carbene precursors yields CaproGlu. The first-of-its-kind low-viscosity prepolymer is VOC-free and requires no photoinitiators. Grafted diazirine end-groups form carbene diradicals upon low energy UVA (365 nm) activation that immediately crosslink tissue surfaces; no pre-heating or animal-derived components are required. The hydrophobic polymeric environment enables metastable functional groups not possible in formulations requiring solvents or water. Activated diazirine within CaproGlu is uniquely capable of crosslinking all amino acids, even on wet tissue substrates. CaproGlu undergoes rapid liquid-to-biorubber transition within seconds of UVA exposure-features not found in any other bioadhesive. The exceptional shelf stability of CaproGlu allows gamma sterilization with no change in material properties. CaproGlu wet adhesiveness is challenged against current unmet clinical needs: anastomosis of spliced blood vessels, anesthetic muscle patches, and human platelet-mediating coatings. The versatility of CaproGlu enables both organic and inorganic composites for future bioadhesive platforms.

Local Anesthetic Toxicity in the Geriatric Population

This article provides a concise overview of local anesthetic systemic toxicity, its history, mechanisms, risk factors, prevention, clinical presentation, and treatment, with a special emphasis on issues specific to the geriatric population. The authors used MEDLINE, Scopus, and Google Scholar to search for original research articles (human and animal studies), registries data, case reports, review articles, and pertinent online publications using the combinations of the following search terms: local anesthetics, local anesthetic systemic toxicity, intralipid, lipid emulsion, Exparel, ultrasound-guidance, regional anesthesia, lidocaine, bupivacaine, ropivacaine, cocaine, procaine, tetracaine, levobupivacaine, liposomal bupivacaine, lignocaine. Local anesthetic systemic toxicity continues to occur despite the use of putatively less cardiotoxic formulations of local anesthetics and more common use of ultrasound guidance. The elderly appear to be at a disproportionately increased risk for toxicity owing to the presence of relevant comorbidities and decreased muscle mass. Examination of recent case reports involving patients over the age of 65 years demonstrates that inadvertent overdosing is responsible for some cases of local anesthetic systemic toxicity. Elderly patients are at increased risk of local anesthetic systemic toxicity. When considering use of local anesthetics in older patients, special attention should be paid to the presence of systemic disease and muscle wasting. The safety of regional anesthesia and multi-modal analgesia among these at-risk patients will be improved by educating physicians and staff to recognize and manage local anesthetic systemic toxicity.

Lipid-based nanoparticle formulations for small molecules and RNA drugs

Introduction: Liposomes and lipid-based nanoparticles (LNPs) effectively deliver cargo molecules to specific tissues, cells, and cellular compartments. Patients benefit from these nanoparticle formulations by altered pharmacokinetic properties, higher efficacy, or reduced side effects. While liposomes are an established delivery option for small molecules, Onpattro® (Sanofi Genzyme, Cambridge, MA) is the first commercially available LNP formulation of a small interfering ribonucleic acid (siRNA). Areas covered: This review article summarizes key features of liposomal formulations for small molecule drugs and LNP formulations for RNA therapeutics. We describe liposomal formulations that are commercially available or in late-stage clinical development and the most promising LNP formulations for ASOs, siRNAs, saRNA, and mRNA therapeutics. Expert opinion: Similar to liposomes, LNPs for RNA therapeutics have matured but still possess a niche application status. RNA therapeutics, however, bear an immense hope for difficult to treat diseases and fuel the imagination for further applications of RNA drugs. LNPs face similar challenges as liposomes including limitations in biodistribution, the risk to provoke immune responses, and other toxicities. However, since properties of RNA molecules within the same group are very similar, the entire class of therapeutic molecules would benefit from improvements in a few key parameters of the delivery technology.

[Stocktaking of local anesthetics 2020]

For decades local anesthetics have proven to be safe and effective drugs in the clinical practice, crucially promoting the enormous achievements in regional anesthesia. Meanwhile, it is a well-known fact that local anesthetics are much more than just "simple" sodium channel blockers. They also interact with numerous other ion channels and subcellular structures, enhancing nerve blockade and resulting in systemic "alternative" effects, which can sometimes even be clinically used. By the simultaneous administration of various adjuvants (e.g., opioids, corticosteroids and α₂-receptor agonists) attempts are made to prolong the time of action of local anesthetics after a single administration in order to achieve the best possible improvement in postoperative analgesia. In this context, ultralong-acting local anesthetics, such as liposomal bupivacaine, which at least theoretically can provide a sensory nerve block for several days, have been developed and clinically introduced. The coming years will show whether these approaches will develop into genuine alternatives to the personnel and cost-intensive continuous nerve blockades.Local anesthetic-induced systemic toxicity is meanwhile rare but still a potentially life-threatening event, frequently resulting from accidental intravascular injection or extensive systemic resorption. Consequently, slow and fractional application of these agents with intermittent aspiration helps to prevent toxic sequelae. If toxic symptoms occur, however, the intravenous infusion of 20% lipid solutions in addition to basic treatment measures can enhance the success of treatment.

The Role of Exparel Plus Meloxicam for Postoperative Pain Management

PURPOSE OF REVIEW

Acute postoperative pain reduction is a major target against the opioid crisis. While opioids have traditionally been the mainstay for postoperative analgesia, current practice has focused on a multimodal approach to pain control, including ultrasound-guided blocks with longer acting local anesthetic agents.

RECENT FINDINGS

Non-steroidal anti-inflammatory drugs (NSAIDs), such as meloxicam, are an important class of medications utilized to manage pain in the perioperative period. An additional treatment used in perioperative or postoperative pain relief is Exparel, a bupivacaine (sodium channel blocker) liposomal injectable suspension with a 3-4-day duration of action. The long-acting mechanism and formulation of Exparel consistently has demonstrated decreased opioid use and pain scores in patients undergoing many different surgical procedures. A concern is that pH negatively alters the efficacy of bupivacaine, as in cases of inflamed tissue and acidic fluid pH. For this reason, a combination medication with both meloxicam and bupivacaine has been developed, which normalizes pH and has anti-inflammatory and anti-pain conduction properties. Clinical studies demonstrate that this combination agent can be extremely beneficial in treating postoperative pain. This manuscript summarizes the newest developments with regard to liposomal bupivacaine and the non-steroidal meloxicam, their roles in effective treatment of postoperative pain, contraindications, special considerations of using these medications, and future considerations. HTX-011 pairs up a new extended-release formulation of the local anesthetic bupivacaine with meloxicam, a well-established non-steroidal anti-inflammatory drug (NSAID).

Advances of Nano-Structured Extended-Release Local Anesthetics

Extended-release local anesthetics (LAs) have drawn increasing attention with their promising role in improving analgesia and reducing adverse events of LAs. Nano-structured carriers such as liposomes and polymersomes optimally meet the demands of/for extended-release, and have been utilized in drug delivery over decades and showed satisfactory results with extended-release. Based on mature technology of liposomes, EXPAREL, the first approved liposomal LA loaded with bupivacaine, has seen its success in an extended-release form. At the same time, polymersomes has advances over liposomes with complementary profiles, which inspires the emergence of hybrid carriers. This article summarized the recent research successes on nano-structured extended-release LAs, of which liposomal and polymeric are mainstream systems. Furthermore, with continual optimization, drug delivery systems carry properties beyond simple transportation, such as specificity and responsiveness. In the near future, we may achieve targeted delivery and controlled-release properties to satisfy various analgesic requirements.

A Review of Regional Anesthesia in Infants

Regional anesthesia provides effective anesthesia and pain relief in infants with age-specific data attesting to safety and efficacy. Regional anesthesia decreases exposure to opioids and general anesthetic agents and associated adverse drug effects, suppresses the stress response, and provides better hemodynamic stability compared to general anesthesia. Regional anesthesia can prevent long-term behavioral responses to pain. As a result, the overall number and variety of nerve blocks being used in infants is increasing. While neuraxial blocks are the most common blocks performed in infants, the introduction of ultrasound imaging and a better safety profile has advanced the use of peripheral nerve blocks. Infant-specific pharmacokinetic and pharmacodynamic data of local anesthetic medications are reviewed including risk factors for the accumulation of high serum levels of unbound, pharmacologically active drug. Bupivacaine accumulates with continuous infusion and 2-chloroprocaine can be used as an alternative. Local anesthetic systemic toxicity has the highest incidence in infants less than 6 months of age and is associated with bolus dosing and penile nerve blocks. Local anesthetic toxicity is treated by securing the airway, suppression of seizure activity and implementation of cardiopulmonary resuscitation. Administration of intralipid (intravenous lipid emulsion) is initiated at the first sign of toxicity. A high level of expertise in regional anesthesia is needed when treating infants due to their unique development.

Formulation and optimisation of novel transfersomes for sustained release of local anaesthetic

Objective

To investigate the effect of formulation parameters on the preparation of transfersomes as sustained-release delivery systems for lidocaine and to develop and validate a new high-performance liquid chromatography (HPLC) method for analysis.

Method

Taguchi design of experiment (DOE) was used to optimise lidocaine-loaded transfersomes in terms of phospholipid, edge activator (EA) and phospholipid : EA ratio. Transfersomes were characterised for size, polydispersity index (PDI), charge and entrapment efficiency (%EE). A HPLC method for lidocaine quantification was optimised and validated using a mobile phase of 30%v/v PBS (0.01 m) : 70%v/v Acetonitrile at a flow rate of 1 ml/min, detected at 255 nm with retention time of 2.84 min. The release of lidocaine from selected samples was assessed in vitro.

Key findings

Transfersomes were 200 nm in size, with PDI ~ 0.3. HPLC method was valid for linearity (0.1–2 mg/ml, R2 0.9999), accuracy, intermediate precision and repeatability according to ICH guidelines. The %EE was between 44% and 56% and dependent on the formulation parameters. Taguchi DOE showed the effect of factors was in the rank order : lipid : EA ratio ˃ EA type ˃ lipid type. Optimised transfersomes sustained the release of lidocaine over 24 h.

Conclusion

Sustained-release, lidocaine-loaded transfersomes were successfully formulated and optimised using a DOE approach, and a new HPLC method for lidocaine analysis was developed and validated.

Mastectomy is no longer an indication for postoperative opioid prescription at discharge

BACKGROUND

A 10-step protocol employing multimodal analgesia was implemented in patients undergoing mastectomy to decrease the quantity of opioids prescribed at discharge.

METHODS

Patients who received the Enhanced Recovery After Surgery (ERAS) protocol were compared to a control group. Inpatient and discharge prescription of opioids were compared using oral morphine equivalents (OMEs), along with postoperative pain scores.

RESULTS

Between 2017 and 2018, fifty-seven patients were eligible for inclusion: 20 patients received ERAS and 37 received usual care (UC). The ERAS group received a mean of 2.4 (0-13) inpatient OMEs and the UC group received 13.7 (0-80) (p = 0.002). The ERAS group received 2.0 (0-40) OMEs at discharge and the UC group received 59.8 (0-120) (p < 0.001). Postoperative pain scores were significantly lower in the patients who received the ERAS protocol.

CONCLUSIONS

Patients who received the ERAS protocol required less postoperative opioids and reported lower pain scores when compared to a control group.