For those of you who have used lidocaine patches, how long till you know if they're going to help? My son's been using them for two days and hasn't found them particularly helpful. He gets more relief from the heating pad, but they said not to use the heating pad with the patch on.

The doctor's office said to give it a few days, but it seems like something topical would have pretty immediate results if it was going to help.

Thanks.