Background: Chronic pain remains a major clinical challenge, which is often resistant to conventional treatments. Spinal cord stimulation has been used for decades to manage refractory pain, traditionally relying on open-loop systems with fixed-output stimulation. However, these systems fail to account for physiological variability, leading to inconsistent pain relief. Closed-loop spinal cord stimulation represents a significant advancement by utilizing evoked compound action potentials to continuously modulate stimulation intensity in real-time, ensuring more stable and effective pain management. Methods: A comprehensive literature review was conducted using PubMed and ClinicalTrials.gov to identify and synthesize relevant published and ongoing studies with a focus on open-loop spinal cord stimulation for managing lower back pain. Results: Clinical trials, including the Avalon and Evoke studies, have demonstrated that closed-loop spinal cord stimulation provides superior pain relief, functional improvement, and reduced opioid dependence compared to traditional open-loop systems. Patients receiving closed-loop stimulation reported significantly higher rates of sustained pain reduction, improved quality of life, and fewer complications related to overstimulation. Emerging studies suggest its potential for conditions beyond back pain, such as neuropathic pain, cancer-related pain, and Raynaud’s phenomenon. Furthermore, cost-effectiveness analyses indicate that closed-loop spinal cord stimulation is a more economically viable treatment option compared to conventional medical management and open-loop systems. Conclusions: Closed-loop spinal cord stimulation represents a transformative development in neuromodulation, offering personalized and adaptive pain management that is distinct from open-loop spinal cord stimulation. Further research is warranted to explore its long-term durability, broader applications, and integration with emerging technologies in pain management.

Although traditional opioids such as morphine and oxycodone are commonly used in the management of acute postoperative pain, novel opioids may play a role as alternatives that provide potent pain relief while minimizing adverse effects. In this review, we discuss the mechanisms of action, findings from preclinical studies and clinical trials, and potential advantages of several novel opioids. The more established include oliceridine (biased ligand activity to activate analgesia and downregulate opioid-related adverse events), tapentadol (mu-opioid agonist and norepinephrine reuptake inhibitor), and cebranopadol (mu-opioid agonist with nociceptin opioid peptide activity)—all of which have demonstrated success in the clinical setting when compared to traditional opioids. On the other hand, dinalbuphine sebacate (DNS; semi-synthetic mu partial antagonist and kappa agonist), dual enkephalinase inhibitors (STR-324, PL37, and PL265), and endomorphin-1 analog (CYT-1010) have shown good efficacy in preclinical studies with future plans for clinical trials. Rather than relying solely on mu-opioid receptor agonism to relieve pain and risk opioid-related adverse events (ORAEs), novel opioids make use of alternative mechanisms of action to treat pain while maintaining a safer side-effect profile, such as lower incidence of nausea, vomiting, sedation, and respiratory depression as well as reduced abuse potential.