PGD is a prominent and growing social problem. Unfortunately, there is no established drug treatment for this disorder. Preliminary investigations demonstrate that naltrexone in doses up to 250 mg/day is well tolerated and safe during an 11-week period and may be a viable treatment option for PGD patients with severe urges. The implications of this study extend from PGD to other impulse control disorders, including compulsive shopping, kleptomania, and possibly alcoholism.

Participants are randomly assigned to receive either naltrexone or placebo for 16 weeks. The responses of men and women are compared to determine whether efficacy is distributed in a male:female ratio analogous to that of the PGD population in the United States. A Clinical Global Impression and a Gambling Symptom Scale are used to assess participants.

Inclusion Criteria:

• DSM-IV criteria for Pathological Gambling Disorder
• Moderate or severe gambling urge assessed by the Gambling Symptom Assessment Scale
• No psychiatric drug use for 2 weeks or more
• Score >= 5 on The South Oaks Gambling Screen
• Hamilton Depression Rating Scale and Anxiety Rating score < 26. An increase (up to 10 points) of the scores is allowed unless the subject shows the risks of suicide.
• Completion of complete blood count, urinalysis, liver and thyroid function tests, and pregnancy tests, with no evidence of significant lab abnormalities
• Reliable birth control in women of child-bearing potential