The invention provides short interfering nucleic acids, either single-stranded or double-stranded, that cause RNAi-induced degradation of mRNA from the Nav1.8 sodium channel gene to pharmaceutical compositions comprising such short interfering nucleic acids recombinant vectors comprising such short interfering nucleic acids a method for inhibiting translation of an mRNA a method for inhibiting expression of a polypeptide a method for blocking the membrane potential in a cell a method for blocking the sodium current in a cell and a method for inhibiting chronic pain.