The Use of Long-Acting Liposomal Bupivacaine (Exparel) for Postoperative Pain Control Following Enucleation or Evisceration

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.

Liposomal Bupivacaine Suspension for Pain Control Following Ocular Evisceration Surgery

PURPOSE

To determine the effectiveness of retrobulbar liposomal bupivacaine for controlling postoperative pain following evisceration, compared with 0.75% bupivacaine.

METHODS

Randomized controlled trial, in which the postoperative pain scores from 24 patients who had retrobulbar liposomal bupivacaine after an evisceration were compared with the pain scores from 24 patients eviscerated using 0.75% bupivacaine.

RESULTS

Patients who received liposomal bupivacaine reported significantly less pain at 24 hours (2.0 out of 10, p = 0.01) and 48 hours (2.2 out of 10, p = 0.01) after surgery than patients who received 0.75% bupivacaine (5.7, and 5.0, respectively). The postoperative pain scores at 1 hour and at 7 days did not significantly differ between the 2 groups. Significantly, fewer patients who received liposomal bupivacaine (0%) than patients who received 0.75% bupivacaine (16.7%) returned emergently during the postoperative period for uncontrolled pain (p ≤ 0.001).

CONCLUSIONS

Retrobulbar liposomal bupivacaine is more effective than 0.75% bupivacaine for controlling pain during the first 2 days after evisceration and should be considered for patients undergoing this procedure.

Incidence and Risk Factors of Moderate to Severe Postoperative Pain Following the Placement of Primary and Secondary Orbital Implants: A Prospective Observational Study

PURPOSE

To prospectively explore the incidence and risk factors of moderate to severe pain after primary and secondary orbital implantation following evisceration or enucleation surgery.

METHODS

One hundred eighteen patients under general anesthesia for orbital implantation were enrolled in this study. In 91 patients, primary orbital implantation followed evisceration, and in 27 patients, the implantation was secondary after previous evisceration or enucleation surgery. Medical interventions for all participants were followed by standardized surgical, anesthetic, and analgesic protocols. Postoperative pain (POP) intensity was quantified by an 11-point numerical rating scale within 72 hours after the surgery, numerical rating scale ≥4 was considered moderate to severe POP. Multivariate logistic regression was utilized to identify the risk factors related to the development of POP.

RESULTS

Thirty-five patients (29.7%) displayed moderate to severe POP, particularly within 6 to 24 hours after surgery, which peaked at 24 hours. Of these patients, 26 patients who were unable to tolerate the pain received additional doses of analgesics during in-hospital stay. Logistic regression model revealed that preoperative anxiety (odds ratios = 4.890; p = 0.002), congenital microphthalmia (odds ratios = 14.602; p = 0.038), and surgical time longer than 60 minutes (odds ratios = 5.586; p = 0.001) were significantly associated with moderate to severe POP after orbital implantation.

CONCLUSIONS

Orbital implantation after evisceration or enucleation surgery is likely to cause moderate to severe pain intensity in the early postoperative period. Preoperative anxiety, prolonged surgical time, and congenital microphthalmia were the risk factors.

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.

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).