Chronic pain, including cancer-related pain and neuropathic pain, remains difficult to treat despite many years of extensive preclinical research. Currently, there is a rather short list of medications that can be effectively used to treat chronic pain. One of the clinical issues related to drug therapy is that side effects often develop at or below a drug's therapeutic level. For example, the n-type calcium channel blocker ziconotide was approved for the treatment of severe pain, but its side effects …