Gene May Predict Effectiveness of Medication for Alcoholism
> 2/8/2008 1:17:49 PM

Medication can be used to treat alcoholism, helping patients to both reduce their alcohol consumption and stave off cravings. These medications, however, are only beneficial for some patients, and researchers continue to study the reasons behind differing rates of effectiveness. A study published in this month's Archives of General Psychiatry shows that by genotyping patients, we may to able to identify those who will find a given drug most helpful. In studying the medication naltrexone, these researchers observed that subjects with a certain variation in the opioid receptor gene (OPRM1) were more successful at abstaining from alcohol than subjects without this variation.

The study used data from 604 alcoholics who had participated in the Combined Pharmacotherapies and Behavioral Interventions for Alcohol Dependence (COMBINE) Study. This large study examined various medications and therapies currently used to treat alcoholism and found naltrexone to be effective alone or in addition to combined behavioral intervention (CBI), which involves cognitive-behavioral and motivational therapies. To further investigate these findings, the researchers assigned subjects to take either naltrexone or a placebo during 16 weeks of treatment. All subjects underwent medical management, structured counseling sessions that emphasized the importance of abstaining from alcohol and taking medication. Half of the subjects were randomly assigned to also receive CBI.

Subjects with a variation in OPRM1, those carrying at least one copy of the Asp40 allele, saw more favorable outcomes than subjects without this variation. 87% of carriers who received naltrexone had fewer days of heavy drinking and more days of abstinence from alcohol, while only 49% of carriers in the placebo group achieved the same results. This effect was not seen among those who did not carry the variation, and about 55% of this group, whether they took naltrexone or a placebo, experienced the same outcome.

While 15-25% of humans carry this variation, prevalence differs depending on ethnicity, and this study did not include a diverse enough sample to adequately determine the influence of race and ethnicity on naltrexone's effectiveness. In an analysis of data only from white participants, the researchers found that carriers of the Asp40 allele who took naltrexone were nearly 6 times as likely as the other experimental groups to reach a favorable outcome. When they expanded the analysis to include data from all participants, regardless of race or ethnicity, carriers taking naltrexone were still 3 times as likely to achieve these results.

Genotype and medication had no significant effect on outcome in the group of subjects receiving CBI, an indication that genotyping may be most beneficial for patients not engaged in therapy. While therapy remains a vital component of treatment for alcoholism, physicians who can predict the effectiveness of a given medication will be able to tailor treatment to meet the specific needs of each patient. Continued research on the factors behind a given drug's effectiveness is necessary and will hopefully yield promising results.

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