Old Friends With New Faces: Are Sodium Channel Blockers the Future of Adjunct Pain Medication Management?

Unlabelled: Providers are being asked to decrease the emphasis and overutilization of long-term opioid therapy, but many are left without proper guidance on appropriate utilization of nonopioid therapies. Furthermore, therapeutic options are quite limited and many providers lack confidence in distinguishing available alternatives. When first-line therapy has failed in a patient, there is an apparent lack of knowledge on how to proceed with choosing subsequent therapy. To choose among alternative agents, an understanding of pharmacology, pharmacokinetics, and efficacy in targeting various pain conditions is necessary. This article focuses on the use of the carboxamide class of sodium channel blockers (carbamazepine, oxcarbazepine, eslicarbazepine) for adjunct pain medication management including research updates in pharmacology, pharmacokinetics, and current evidence for pain along with promising areas of research. It is an evidence update for clinical use of sodium channel blockers, clarifies misconceptions regarding their use, and highlights emerging research for improved pain targets that justifies additional study. We performed a complete review of the literature using the search terms, "oxcarbazepine," "carbamazepine," and "eslicarbazepine" in conjunction with "pharmacokinetics," "adverse effects," "pharmacology," "voltage-gated sodium channel subtype," "neuropathic pain," "inflammatory pain," "metabolism," "epoxide metabolite formation," "drug interactions," "CYP450 interactions," "pain phenotype," and "chronic pain management." Databases searched included PubMed and Google Scholar. Package inserts were used for drug structure illustration, adverse reactions, and bioavailability. Pharmacology and pharmacokinetic data were taken from randomized controlled trials evaluating this area as well as in vitro published results. For validity, only peer-reviewed literature was included. Evidence for sodium channel blockers in chronic pain management was limited. This review focuses on highlighting the data available for the use of sodium channel blockers for certain pain syndromes as well as underutilized potential. Emerging literature on sodium channel subtypes and their connection to neuropathic, inflammatory, and mechanical pain transmission is elucidated. The authors also scrutinize literature surrounding the pharmacokinetics of oxcarbazepine and eslicarbazepine to provide clearer guidance to the significance of any drug interactions and refute assumptions made on the basis of structural similarity to carbamazepine and its known undesirable drug interactions. Side effect profiles are outlined and compared, emphasizing the differences between agents. Sodium channel blocker doses used in certain pain syndromes are outlined with a call for further research to better understand their place in chronic pain management. Identification of sodium channel subtypes with links to specific pain conditions and the ability to target them hints at the potential for truly individualized therapy. Sodium channel inhibitors are underutilized on the basis of available evidence, and emerging research has identified this area as promising for additional clinical trials to better guide clinical practice.

Perspective: This article provides a review of the pharmacology, evidence for pain management, and pharmacokinetics of oxcarbazepine, carbamazepine, and eslicarbazepine. There is a disparity in evidence using sodium channel blockers for pain and this article highlights the potential that is currently underutilized. The authors believe this will catalyze interest for further studies.