Extended Release of Bupivacaine from Temperature-responsive Hydrogels Provides Multi-day Analgesia for Postoperative Pain

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

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

Intensity-adjustable pain management with prolonged duration based on phase-transitional nanoparticles-assisted ultrasound imaging-guided nerve blockade

Background

The lack of a satisfactory strategy for postoperative pain management significantly impairs the quality of life for many patients. However, existing nanoplatforms cannot provide a longer duration of nerve blockage with intensity-adjustable characteristics under imaging guidance for clinical applications.

Results

To overcome this challenge, we proposed a biocompatible nanoplatform that enables high-definition ultrasound imaging-guided, intensity-adjustable, and long-lasting analgesia in a postoperative pain management model in awake mice. The nanoplatform was constructed by incorporating perfluoropentane and levobupivacaine with red blood cell membranes decorated liposomes. The fabricated nanoplatform can achieve gas-producing and can finely escape from immune surveillance in vivo to maximize the anesthetic effect. The analgesia effect was assessed from both motor reactions and pain-related histological markers. The findings demonstrated that the duration of intensity-adjustable analgesia in our platform is more than 20 times longer than free levobupivacaine injection with pain relief for around 3 days straight. Moreover, the pain relief was strengthened by repeatable ultrasound irradiation to effectively manage postoperative pain in an intensity-adjustable manner. No apparent systemic and local tissue injury was detected under different treatments.

Conclusion

Our results suggest that nanoplatform can provide an effective strategy for ultrasound imaging-guided intensity-adjustable pain management with prolonged analgesia duration and show considerable transformation prospects.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01707-z.