Methadone has been an effective and inexpensive therapy in the management of chronic pain and opioid dependence. However it has been associated with sudden, unexpected deaths. Two mechanisms have been suggested, increased drug concentration in the blood, and a change in the heart rhythm. This study will look at blood samples for drug levels and genetic components and EKG's (a noninvasive test which reveals heart rhythm). There will be no intervention.

Inclusion Criteria:

• must be 18 years of age or older; eligible for methadone treatment as judged by Discovery House criteria
• must sign informed consent for methadone treatment prior to being approached for this study
• must sign a written informed consent for this study
• is willing and has a means to return for all scheduled follow-up visits

Exclusion Criteria:

• pregnancy, participation in any other clinical trial involving investigational or marketed products with 30 days prior to entry into this study; current use of an inducer/inhibitor of known enzymes involved with methadone metabolism
• use of methadone in the 30 days prior to study enrollment; concomitant use of QT prolonging drugs
• considered by the treatment physician to be ineligible for methadone treatment; hepatic function panel indicates chronic liver disease.

Subjects initiating methadone treatment for opioid addiction who meet elibitility criteria.

All-cause mortality, serious, and other (not including serious) adverse events were not monitored/assessed.

The principal limitations are small sample size and the limited number of genetic variants tested. Also, study endpoints were not examined beyond 21 days of treatment; thus the durability of study findings over longer time periods is not known.