The invention features a method for inhibiting one or more voltage-gated ionchannels in a cell by contacting the cell with (i) a first compound that activatesa channel-forming receptor that is present on nociceptors and/or pruriceptorsand (ii) a second compound that inhibits one or more voltage-gated ion channelswhen applied to the internal face of the channels but does not substantially inhibitsaid channels when applied to the external face of the channels, wherein the secondcompound is capable of entering nociceptors or pruriceptors through the channel-formingreceptor when the receptor is activated. The invention also features a quarternaryamine derivative or other permanently or transiently charged derivative ofa compound that inhibits one or more voltage-gated ion channels when appliedto the internal face of the channels but does not substantially inhibit said channelswhen applied to the external face of the channels.
