Role of voltage-gated sodium channel blockers in the treatment of chronic pain: Potential uses in clinical practice based on available evidence

Carbamazepine conquers spinal GAP43 deficiency and sciatic Nav1.5 upregulation in diabetic mice: novel mechanisms in alleviating allodynia and hyperalgesia

This work tested the role of carbamazepine in alleviating alloxan-induced diabetic neuropathy and the enhancement of spinal plasticity. Mice were randomized into four groups: normal, control, carbamazepine (25-mg/kg) and carbamazepine (50-mg/kg). Nine weeks after induction of diabetes, symptoms of neuropathy were confirmed and carbamazepine (or vehicle) was given every other day for five weeks. After completing the treatment period, mice were sacrificed and the pathologic features in the spinal cord and the sciatic nerves were determined. The spinal cords were evaluated for synaptic plasticity (growth associated protein-43, GAP43), microglia cell expression (by CD11b) and astrocyte expression (glial fibrillary acidic protein, GFAP). Further, sciatic nerve expression of Nav1.5 was measured. Results revealed that carbamazepine 50 mg/kg prolonged the withdrawal threshold of von-Frey filaments and increased the hot plate jumping time. Carbamazepine improved the histopathologic pictures of the sciatic nerves and spinal cords. Spinal cord of carbamazepine-treated groups had enhanced expression of GAP43 but lower content of CD11b and GFAP. Furthermore, specimens from the sciatic nerve indicated low expression of Nav1.5. In conclusion, this work provided evidence, for the first time, that the preventive effect of carbamazepine against diabetic neuropathy involves correction of spinal neuronal plasticity and glia cell expression.

[Update in the pharmacological treatment of neuropathic pain]

We provide an updated review of the pharmacological treatment of neuropathic pain, with emphasis on the latest evidence-based recommendations. Drugs proposed as first line include tricyclic antidepressants (particularly amitriptyline), serotonin-noradrenaline reuptake inhibitors (particularly duloxetine), pregabalin and gabapentin. Second-line treatments include 5% lidocaine medicated plasters and capsaicin 8% patches, only for peripheral neuropathic pain and tramadol; whereas potent opioids and botulinum toxin A (for peripheral neuropathic pain) are considered third-line treatments. Future perspectives include the development of new drugs and a more personalised therapeutic approach, which is made possible by recent progress in the assessment and understanding of neuropathic pain.

Emerging therapies in clinical development and new contributions for neuropathic pain

Neuropathic pain is very challenging to manage because of the heterogeneity of aetiologies, symptoms, and underlying mechanisms. Conventional oral therapies have been limited by negative factors such as systemic side effects, drug-drug interactions, slow onset of action, the need for titration, multiple daily dosing, as well as the potential risk of addiction, dependence, withdrawal symptoms and abuse. Therefore, new therapeutic perspectives are justified. New drugs that act on different therapeutic targets are currently in preclinical development or in their first phases of clinical development. In this review, focus will be directed specifically on new pharmacological treatments for neuropathic pain for which clinical data are already available, including older and known drugs with new data on their anti-neuropathic activity.