The purpose of this study is to develop repetitive transcranial magnetic stimulation (rTMS) as a potential treatment for pain in individuals on prescription opioid medication. Repetitive TMS is a non-invasive technique that uses magnetic pulses to temporarily stimulate specific brain areas in awake people (without the need for surgery, anesthetic, or other invasive procedures). This study will test whether 10 days of rTMS over the prefrontal cortex can produce a reduction in perception of pain and the desire to use opiates. TMS has been approved by the FDA as an investigational tool as well a therapy for depression.