Investigation of Naltrexone for Pathological Gambling

Inclusion Criteria:

1. Men or women over age 18
2. Current DSM-IV PG Diagnosis as determined by a score of ≥ 5A criteria and B criterion present on the SCI-PG and a score ≥ 5 on the SOGS
3. Gambling behavior within 2 weeks prior to enrollment
4. For women, stable use of a medically accepted form of contraception and negative results on urine pregnancy test at study onset
5. Currently entering, enrolled, or interested in treatment for PG

Exclusion Criteria:

1. Gambling that does not meet DSM-IV criteria for PG
2. Unstable medical illness or clinically significant abnormalities on laboratory tests, EKG, or physical examination at screen
3. Past or current acute hepatitis or liver failure
4. History of renal impairment
5. Current or recent (within one week) treatment with an opioid agonist/opioid analgesic or current opioid withdrawal
6. Opiate agonist maintenance therapy (e.g. methadone)
7. Known sensitivity to opioid antagonists
8. Current pregnancy or lactation, or inadequate contraception in women of childbearing potential
9. A need for medication with unfavorable interactions with naltrexone
10. Clinically significant suicidality
11. Lifetime history of dementia, schizophrenia, or any psychotic disorder determined by SCID
12. Clinically significant cognitive impairment
13. Previous treatment with naltrexone or nalmefene
14. Treatment with investigational medication or depot neuroleptics within 3 months
15. Lack of proficiency in written and spoken English
16. Unable to travel to study sites for appointments