This research is part of a set of studies whose purpose is to test whether tramadol can be
used for the treatment of opioid addiction. Tramadol is already available in the United
States as a pain medicine marketed as Ultram. It has effects similar to morphine, and it may
also have effects similar to other drugs like stimulants. The doses of tramadol used in this
study are higher than those generally used for the treatment of pain. To be in this study a
participant must be a user of opioids (drugs like heroin) and stimulants (drugs like
cocaine), but cannot be addicted to either. The person must be between 21-55 years old, and
generally healthy. Up to 12 people will take part in this study.