In 2001 Suck Won Kim, M.D., a professor of psychiatry at the University of
Minnesota, published results of a trial exploring the possible value of
treating pathological gambling with the opiate antagonist naltrexone.
Naltrexone was found to be superior to a placebo in countering symptoms of the
disorder. However, the medication caused liver enzyme problems in subjects who
took over-the-counter pain medications at the same time.
Subsequently, Kim helped other pathological-gambling investigators design a
study to learn whether the opiate antagonist nalmefene, which is related to
naltrexone but purportedly safer, might also counter symptoms of pathological
gambling. "Results are quite promising," lead investigator Jon
Grant, M.D., J.D., an associate professor of psychiatry at the University of
Minnesota, recently said (Psychiatric News, March 18, 2005).
The results of this study are published in the February American
Journal of Psychiatry.
The study took place at 15 outpatient treatment centers throughout the
United States. Subjects were recruited via newspaper ads and medical
referrals. The researchers ended up with 207 individuals who met criteria for
a DSM-IV pathological gambling disorder.
The 207 subjects were then randomized to receive, over a 16-week period, 25
mg daily of nalmefene, 50 mg daily of nalmefene, 100 mg daily of nalmefene, or
The primary outcome measure was the Yale-Brown Obsessive-Compulsive Scale
Modified for Pathological Gambling, which is used to rate gambling thoughts,
urges, and behaviors within the previous week. Subjects were assessed with it
throughout the study. For overall treatment response, subjects with a Clinical
Global Improvement score of "much improved" or "very much
improved" at the last available evaluation point were considered
Fifty-nine percent of the 25 mg nalmefene group; 48 percent of the 50 mg
nalmefene group; 42 percent of the 100 mg nalmefene group, and 34 percent of
the placebo group were found to be responders (see chart).
Why the 100 mg and 50 mg nalmefene groups did not respond as well as the 25
mg nalmefene group is not clear. However, it may be because these higher doses
caused more intolerable side effects.
So it looks as if nalmefene can reduce gambling symptoms in a number of
pathological gamblers and that the ideal dose for doing so might be 25 mg a
day, since this dose appeared to be quite effective while producing few
However, optimal dosing and titration can be determined only from further
research, Grant and his colleagues pointed out in their report. The same is
true for determining the optimal length of treatment.
"It is possible that a longer course of therapy could result in
continued and even greater reduction in gambling symptoms," they
Grant and his colleagues are currently conducting another study of
nalmefene in pathological gamblers, he told Psychiatric News. This
one is taking place at 20 different sites. Because it has obtained rights to
nalmefene, Somaxon Pharmaceuticals in San Diego is also launching several
trials of nalmefene to treat pathological gambling, Grant said.
Meanwhile, the results achieved from the just-published study illustrate
that "psychiatry is finally gaining rational treatments for its
illnesses, treatments based on demonstrated brain mechanisms," Carol
Tamminga, M.D., and Eric Nestler, M.D., Ph.D., wrote in an accompanying
editorial. They are professors of psychiatry and neuroscience at the
University of Texas Southwestern Medical
In other words, they explained, the study was based on the hypothesis that
pathological gambling is an addiction disorder and that a drug known to
counter addiction could thwart pathological gambling as well.
"Multicenter Investigation of the Opioid Antagonist Nalmefene
in the Treatment of Pathological Gambling" is posted at<http://ajp.psychiatryonline>
under the February issue. ▪