Pain continues to be a major health problem with tremendous financial, social and psychological costs. Conservative estimates put the cost of pain to the US economy well into the hundreds of billions of dollars per year as a result of associated medical expenses and lost wages with a significant minority of Americans suffering from persistent or recurrent pain syndromes throughout the most productive years of their lives. Just one pain syndrome, migraine headache, directly impacts 20% of the adult population. Yet, there remain few if any effective therapies devoid of serious side effects that are currently available to treat pain, particularly persistent or recurrent pain associated with syndromes
