In the U.S., it is estimated that approximately 1.4-2.8 percent of the adult population suffer from pathological gambling and in Europe the number varies by country between 1-3 percent. Pathological gambling was included in the Diagnostic and Statistical Manual of Mental Disorders (DSM) in 1980, but there is no approved drug therapy available for this condition. Psycho-social therapy is currently the main treatment modality for patients suffering from pathological gambling. To the company's knowledge, the now completed study is the first industry sponsored large scale phase II clinical study in this indication. In terms of suitability for pharmacotherapy, pathological gambling has been considered a representative condition within a variety of impulse control disorders (such as kleptomania, compulsive shopping, pyromania).
A University of Minnesote study showed that low-dose (25 mg/day) nalmefene resulted in "a statistically significant reduction in severity of pathological gambling", but higher doses (>50 mg/day) made the side effects too bad.
On the other hand, Somaxon Pharmaceuticals found that there was no significant impact on gambling behavior.