Understanding analgesic concepts does not need to be complicated. WEX Pharmaceuticals is determined to make pain management both achievable and easily understood, by providing insights into how pain operates and how certain treatments alleviate these conditions. Here, we discuss what sodium channel blockers are, how they work, and the conditions they help to manage.

Sodium channel blockers (SCBs) are a diverse, varied class of medications that are used to treat a wide array of ailments. In some instances, a single SCB can be prescribed to treat two or more disparate conditions. To understand how SCBs have such medical versatility, it is important to understand how sodium channels work, and how SCBs interact with them.

Sodium Channel Blockers (SCBs): Their Function

As mentioned in our previous article about Tetrodotoxin (TTX), sodium channels are integral transmembrane proteins – proteins that span the plasma membranes of various cell types throughout the body – that regulate the flow of sodium ions into certain cells. When action potential is triggered, sodium channels allow the flow of sodium ions into cells, which enables higher level processes, such as the feeling of pain sensations. What SCBs do is hinder these processes at the cellular level by blocking the flow of sodium through these channels, thereby stopping these processes at the source.

As sodium channels are responsible for many bodily processes, SCBs are employed in treating a wide range of medical conditions related to sodium current propagation. Here are some common SCBs and what they are used to treat:

Lidocaine

Lidocaine is a SCB used primarily as an anaesthetic in dentistry, as its numbing capabilities allow for dentists to perform routine dental procedures without the need for opioids or stronger anaesthetics.[1] In addition to this, Lidocaine has been used in the regulating of cardiac arrhythmias (irregular heartbeats), as it has been shown to regulate sinus rhythm back to normal levels.[2]

Phenytoin

Also known under the brand name Dilantin, Phenytoin is an anticonvulsant (anti-seizure medication) that is used to prevent grand mal seizures. By targeting the cerebral cortex, Phenytoin hinders the feedback necessary for maximal seizure activity, thus preventing seizures.[3] As with other SCBs, Phenytoin has shown efficacy in treating multiple medical conditions. Like Lidocaine, Phenytoin has antiarrhythmic properties and can also be used to treat polymorphic ventricular tachycardia, a genetic disorder known to cause arrythmias.[4]

Carbamazepine

Touched upon in our article on CINP was the use of anticonvulsants to treat neuropathic pain. Carbamazepine is such a drug, and is one of the many SCBs (including Lidocaine) used to treat different pain conditions. While primarily an anti-seizure medication, Carbamazepine has shown some mildly positive efficacy in treating both painful diabetic neuropathy and fibromyalgia (a chronic pain syndrome), although this has not reached clinical consensus.[5] There has also been research concerning Carbamazepine’s ability to treat alcohol withdrawal symptoms, which has produced encouraging results.[6]

Drawbacks

Though SCBs have shown impressive versatility in treating a myriad of different ailments, many SCBs have some drawbacks that limit their potential. Lidocaine has in some cases been known to trigger serious allergic reactions, and can sometimes exacerbate cardiac concerns rather than treat them.[7] In addition to this, some SCBs cross the blood-brain barrier, a structure which regulates the passage of molecules between the circulatory and nervous systems. When this occurs, SCBs can cause certain adverse effects in addition to their intended functions, such as drowsiness and respiratory depression.[8]

SCBs play a vital role in medicine. From treating pain conditions, to preventing seizures, to stabilizing heartbeats, they have improved the lives of many patients. Further study into their efficacy, and how best to apply SCBs so that their benefits sufficiently outweigh their potential negatives, is important to ensure the best medical outcomes for patients taking these medications. Fortunately, there has been promising new research into certain SCBs that do not have some of these drawbacks, including one that does not cross the blood-brain barrier: Tetrodotoxin (TTX). Next week, we will discuss TTX, how it differs from other SCBs, and these practical applications.

[1] Bahar, E., & Yoon, H. (2021). Lidocaine: A local anesthetic, its adverse effects and management. Medicina, 57(8), 782. https://doi.org/10.3390/medicina57080782

[2] Daraz, Y. M., & Abdelghffar, O. H. (2022). Lidocaine infusion: An antiarrhythmic with neurologic toxicities. Cureus. https://doi.org/10.7759/cureus.23310

[3] Yaari, Y., Selzer, M. E., & Pincus, J. H. (1986). Phenytoin: Mechanisms of its anticonvulsant action. Annals of Neurology, 20(2), 171–184. https://doi.org/10.1002/ana.410200202

[4] Yager, N., Wang, K., Keshwani, N., & Torosoff, M. (2015). Phenytoin as an effective treatment for polymorphic ventricular tachycardia due to QT prolongation in a patient with multiple drug intolerances. BMJ Case Reports. https://doi.org/10.1136/bcr-2015-209521

[5] Wiffen, P. J., Derry, S., Moore, R. A., & Kalso, E. A. (2014). Carbamazepine for chronic neuropathic pain and fibromyalgia in adults. Cochrane Database of Systematic Reviews, 2019(5). https://doi.org/10.1002/14651858.cd005451.pub3

[6] Barrons, R., & Roberts, N. (2009). The role of Carbamazepine and Oxcarbazepine in alcohol withdrawal syndrome. Journal of Clinical Pharmacy and Therapeutics, 35(2), 153–167. https://doi.org/10.1111/j.1365-2710.2009.01098.x

[7] Daraz, Y. M., & Abdelghffar, O. H. (2022). Lidocaine infusion: An antiarrhythmic with neurologic toxicities. Cureus. https://doi.org/10.7759/cureus.23310

[8] Dokken, K. (2024, March 2). Sodium channel blocker toxicity. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK534844/