Peptide of between 5 and 8 amino acids capable of decreasing the activity and/or signal of at least one type of sodium channel; its acceptable isomers, salts, solvates and/or mixtures thereof, wherein the peptide comprises the sequence of formula: R 1 -AA1-AA2-AA3-AA4-AA5-AA6-R 2 (R 1 -SEQ ID NO: 7-R 2) wherein the peptide is selected from: - R 1 -Arg-Trp-Gln-Lys-Asn-Gln-R 2; - R 1 -Lys-Arg-Arg-Tyr-Tyr-Cys-R 2; or - R 1 -Lys-His-Arg-Ser-Tyr-R 2 - R 1 -Lys-Asp-Arg-Val-Tyr-R 2; - R 1 -Ile-Glu-Pro-Tyr-Tyr-Val-R 2; or - R 1 -Lys-Lys-His-Phe-Trp-Ala-R 2 R 1 is selected from H, substituted or unsubstituted non-cyclic aliphatic, substituted or unsubstituted alicyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted heteroarylalkyl, substituted or unsubstituted aryl, substituted or unsubstituted aralkyl and R 5 -CO-, wherein R 5 is selected from the group formed by substituted or unsubstituted C 1 -C 24 alkyl radical, substituted or unsubstituted C 2 -C 24 alkenyl, substituted or unsubstituted C 2 -C 24 alkynyl, substituted or unsubstituted C 3 -C 24 cycloalkyl, substituted or unsubstituted C 5 -C 24 cycloalkenyl, substituted or unsubstituted C 8 -C 24 cycloalkynyl, substituted or unsubstituted C 6 -C 30 aryl, substituted or unsubstituted C 7 -C 24 aralkyl, substituted or unsubstituted heterocyclyl ring of 3 to 10 members, and substituted or unsubstituted heteroarylalkyl of 2 to 24 carbon atoms and 1 to 3 atoms other than carbon and an alkyl chain of 1 to 6 carbon atoms; and R 2 is selected from H, -NR 3 R 4 -, -OR 3 and -SR 3, wherein R 3 and R 4 are independently selected from H, substituted or unsubstituted non-cyclic aliphatic group, substituted or unsubstituted alicyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted heteroarylalkyl, substituted or unsubstituted aryl, and substituted or unsubstituted aralkyl; alternatively, R 1 and R 2 are absent and AA1 is directly bound to the last amino acid of the peptide. wherein the peptide is selected from: - R 1 -Arg-Trp-Gln-Lys-Asn-Gln-R 2; - R 1 -Lys-Arg-Arg-Tyr-Tyr-Cys-R 2; or - R 1 -Lys-His-Arg-Ser-Tyr-R 2 - R 1 -Lys-Asp-Arg-Val-Tyr-R 2; - R 1 -Ile-Glu-Pro-Tyr-Tyr-Val-R 2; or - R 1 -Lys-Lys-His-Phe-Trp-Ala-R 2 - R 1 -Arg-Trp-Gln-Lys-Asn-Gln-R 2; - R 1 -Lys-Arg-Arg-Tyr-Tyr-Cys-R 2; or - R 1 -Lys-His-Arg-Ser-Tyr-R 2 - R 1 -Lys-Asp-Arg-Val-Tyr-R 2; - R 1 -Ile-Glu-Pro-Tyr-Tyr-Val-R 2; or - R 1 -Lys-Lys-His-Phe-Trp-Ala-R 2 R 1 is selected from H, substituted or unsubstituted non-cyclic aliphatic, substituted or unsubstituted alicyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted heteroarylalkyl, substituted or unsubstituted aryl, substituted or unsubstituted aralkyl and R 5 -CO-, wherein R 5 is selected from the group formed by substituted or unsubstituted C 1 -C 24 alkyl radical, substituted or unsubstituted C 2 -C 24 alkenyl, substituted or unsubstituted C 2 -C 24 alkynyl, substituted or unsubstituted C 3 -C 24 cycloalkyl, substituted or unsubstituted C 5 -C 24 cycloalkenyl, substituted or unsubstituted C 8 -C 24 cycloalkynyl, substituted or unsubstituted C 6 -C 30 aryl, substituted or unsubstituted C 7 -C 24 aralkyl, substituted or unsubstituted heterocyclyl ring of 3 to 10 members, and substituted or unsubstituted heteroarylalkyl of 2 to 24 carbon atoms and 1 to 3 atoms other than carbon and an alkyl chain of 1 to 6 carbon atoms; and R 2 is selected from H, -NR 3 R 4 -, -OR 3 and -SR 3, wherein R 3 and R 4 are independently selected from H, substituted or unsubstituted non-cyclic aliphatic group, substituted or unsubstituted alicyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted heteroarylalkyl, substituted or unsubstituted aryl, and substituted or unsubstituted aralkyl; alternatively, R 1 and R 2 are absent and AA1 is directly bound to the last amino acid of the peptide.