NEW ORLEANS—Outpatient IV infusions of lidocaine failed to reliably confer long-term analgesic benefits in patients with chronic neuropathic pain syndromes, a new analysis concluded.

“Although IV lidocaine administration for chronic neuropathic pain management has recently gained significant attention, studies show conflicting results,” said Anke Wang, MD, a resident at the NYU Langone School of Medicine, in New York City. “Some studies found that lidocaine is effective in breaking the pain cycle, while others concluded limited benefit after the completion of the infusion.”

Given the conflicting results, Wang and her colleagues attempted to determine a general consensus on the utility of IV lidocaine administration for the management of chronic neuropathic pain. They searched the PubMed and EMBASE databases from inception through November 2021 for relevant studies examining the efficacy of IV lidocaine in the management of neuropathic pain. Only original research published in English was considered; letters to the editor, systematic reviews/meta-analyses, case reports and case series were excluded. Full-text reviews were performed independently by two reviewers.

“There is no universal definition of short-term pain or long-term pain relief,” Wang said in an interview with Pain Medicine News. “For short-term pain relief, we wanted to capture a time point greater than 5 half-lives to ensure clearance of the medication from the body. Given lidocaine’s half-life of 60 to 120 minutes, we considered pain relief up to and including 24 hours after the infusion as short-term pain relief.

“Pain relief lasting more than 24 hours was then classified as long-term pain relief,” she said. “Many studies continued to assess patients’ pain scores for weeks to months after the infusion.”

Reporting at the 2022 annual meeting of the American Society of Anesthesiologists (abstract A2092), Wang noted that data were extracted from 37 studies (including 24 randomized controlled studies), comprising 1,454 patients. The most commonly used pain relief measures were the Visual Analogue Scale, Numeric Pain Rating Scale and Brief Pain Inventory.

The researchers found that lidocaine provided effective short-term pain relief in 32 of the 37 studies (86.5%). In contrast, only eight studies (21.6%) showed sustained pain relief following the infusion. When examining the data on a patient-level basis, the researchers found that 1,058 of 1,178 patients (89.8%) reported pain improvement in the acute setting. By comparison, 330 of 1,140 patients (28.9%) reported long-term pain improvement. Although the included studies examined a variety of neuropathic pain syndromes—including fibromyalgia, trigeminal neuralgia, post-herpetic neuralgia and traumatic neuropathy—no consensus was found on the effectiveness of IV lidocaine for treating any of these individual conditions.

“IV lidocaine appears to provide patients some pain relief on the day of the infusion,” Wang said. “However, only a small minority of patients appear to receive sustained benefits after a single infusion. Most patients will likely require repeated infusions. Unfortunately, there is currently no method of predicting who may have improvements in their pain that extend beyond the completion of the infusion.”

It may also be that higher plasma concentrations of lidocaine are required to achieve long-term analgesic effect, the researchers said. Indeed, many of the studies included in the meta-analysis observed that decreases in patient pain depended on the plasma concentration of lidocaine. On the other hand, increased plasma concentrations of lidocaine also increase the risk for side effects, including changes in blood pressure, heart rate, anxiety and headache.

Perhaps not surprisingly, the researchers said that given these results, they would not recommend routine use of IV lidocaine for management of neuropathic pain. Instead, they recommended other analgesics with more robust evidence supporting their long-term efficacy, including duloxetine, gabapentin and pregabalin.

“Even though IV lidocaine wouldn’t be my first choice for management of neuropathic pain, it has shown promise for use in the intraoperative and acute care settings,” Wang said. “Some patients in the ICU may also benefit from a lidocaine infusion.”

Naum Shaparin, MD, MBA, the director of the Multidisciplinary Pain Program at Montefiore Medical Center, in New York City, said that despite the findings, he believes IV lidocaine still has a place in the treatment of chronic neuropathic pain, although only under specific conditions.

“In a modern setting, when lidocaine is titrated to effect, it may help some people,” Shaparin said. “On the other hand, there are so many other therapeutic options available for neuropathic pain that IV lidocaine infusion has really been relegated to a third-, fourth- or fifth-line option. We never want to remove things from our bag of tricks, but this one is fairly low in terms of priority.

“I think most clinicians would likely start treatment for these patients with gabapentinoids,” he said, “though we also have SNRIs [serotonin–norepinephrine reuptake inhibitors] and tricyclic antidepressants. And then on top of that, we also have interventional treatments such as sympathetic nerve blocks and spinal cord stimulation.

“In fact, many young pain providers have likely never even used IV lidocaine for neuropathic pain,” Shaparin noted.

He recognized that there may still be a subset of neuropathic pain patients who might benefit from IV lidocaine.

“Not everybody is a candidate for spinal cord stimulation and not everybody is a candidate for other types of pharmacotherapy,” he said.

—Michael Vlessides

Shaparin and Wang reported no relevant financial disclosures. The abstract was chosen to be a featured abstract at the meeting.