LAS VEGAS—Neuropathic pain is a tremendous burden on the individual and society and represents a complex mixture of peripheral and central mechanisms, said Sean Mackey, MD, PhD, Redlich Professor and Chief, Pain Medicine Division, Stanford University School of Medicine, Stanford, California.
Excluding low-back pain, painful diabetic neuropathy, postherpetic neuralgia (PHN), cancer-associated neuropathy, and spinal cord injuries account for the majority of cases of neuropathic pain in the United States.
The deleterious effects of neuropathic pain include negative emotions (such as depression, anxiety, and anger), poor sleep, immune impairment, decreased quality of life, and existential suffering, which may lead patients to want to actively end their life, he said.
For these reasons, multidisciplinary treatment approaches for the management of neuropathic pain are the most effective. These include self-management, pharmacologic, psychological, physical/occupational therapy, procedural treatments (eg, trigger point injections, nerve blockage, and spinal drug delivery systems), and complementary and alternative medicine. Collectively, these reflect the biopsychosocial perspective of pain.
Dr. Mackey reviewed the pharmacologic approach to treatment of neuropathic pain, focusing on tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors (SNRIs), anticonvulsants, and over-the-counter products.
Efficacy has been established in a number of small crossover, placebo-controlled trials for the use of tricyclic antidepressants—amitriptyline, clomipramine, desipramine, and nortriptyline—in neuropathic pain, he said. He urged caution especially when using desipramine in patients with a family history of dysrhythmias or sudden cardiac death and noted that of all the tricyclic antidepressants, desipramine overdose is more likely to result in death. In addition, while nortriptyline may be safer, it has more adverse events (AEs), including weight gain and sedation.
The SNRI duloxetine has been shown to decrease diabetic peripheral neuropathic pain (the most common AE is nausea), while anticonvulsants for neuropathic pain include gabapentin for painful diabetic neuropathy and PHN (the most common AEs are dizziness and somnolence); pregabalin for PHN; and low-dose naltrexone (compounded locally) for patients with fibromyalgia. In fact, treating microglia with naltrexone may represent a new therapeutic approach, he said.
Dr. Mackey said a crossover study in 56 patients with neuropathic pain who received 6-week blocks of treatment with gabapentin, nortriptyline, and gabapentin plus nortriptyline found the combination was superior to either agent alone in reducing mean daily pain scores.