Blockers of Skeletal Muscle Nav1.4 Channels: From Therapy of Myotonic Syndrome to Molecular Determinants of Pharmacological Action and Back

The voltage-gated sodium channels represent an important target for drug discovery since a large number of physiological processes are regulated by these channels. In several excitability disorders, including epilepsy, cardiac arrhythmias, chronic pain, and non-dystrophic myotonia, blockers of voltage-gated sodium channels are clinically used. Myotonia is a skeletal muscle condition characterized by the over-excitability of the sarcolemma, resulting in delayed relaxation after contraction and muscle stiffness. The therapeutic management of this disorder relies on mexiletine and other sodium channel blockers, which are not selective for the Na(v)1.4 skeletal muscle sodium channel isoform. Hence, the importance of deepening the knowledge of molecular requirements for developing more potent and use-dependent drugs acting on Na(v)1.4. Here, we review the available treatment options for non-dystrophic myotonia and the structure-activity relationship studies performed in our laboratory with a focus on new compounds with potential antimyotonic activity.

Automated summary

Voltage-gated sodium channels are an important target for drug discovery and are involved in various physiological processes. Blockers of these channels are clinically used in several excitability disorders, including myotonia. However, current treatments are not selective for the specific sodium channel isoform involved in myotonia, highlighting the need for developing more potent and use-dependent drugs.