11 Sep Genetics Plays Role in Who Benefits Most From Naltrexone
Naltrexone is a medication originally developed to disrupt the brain’s sensitivity to the intoxicating effects of opioid drugs and medications. The medication is also FDA-approved for the treatment of alcoholism, and doctors across the U.S. prescribe it to patients affected by this form of addiction. However, not all people affected by alcoholism respond to naltrexone treatment equally well. In a study review published in May 2014 in the journal Addiction, a team of American researchers explored the factors that can potentially increase or decrease the effectiveness of naltrexone-based alcoholism treatment.
Alcoholism (also called alcohol addiction or alcohol dependence) is a common term used to signify the presence of a physical reliance on the daily intake of a baseline amount of alcohol, as well as the presence of symptoms that either reinforce or reflect a physical reliance on drinking. These symptoms include such things as a repeating craving for additional alcohol consumption, a corresponding inability to set effective limits on alcohol consumption, a declining vulnerability to alcohol’s intoxicating effects, the sacrifice of other life priorities for drinking-related concerns and the appearance of a potentially dangerous syndrome called alcohol withdrawal when an established pattern of heavy drinking is halted or abruptly cut down. The American Psychiatric Association (which sets the commonly accepted criteria for diagnosing substance problems in the U.S.) considers alcoholism to be one aspect of alcohol use disorder, a recently established diagnosis that also applies to non-dependent alcohol abuse.
Alcohol functions as a source of addiction because it can reach the brain and trigger lasting alterations in the chemical environment of a brain area known as the pleasure center. Just like opioid drugs and medications, alcohol gains the required brain access by activating sites called opioid receptors, which appear on the surfaces of key nerve cells. When it enters the bloodstream, naltrexone travels to the opioid receptors and establishes a barrier that helps stop alcohol and opioids from reaching the brain. The medication comes in two basic forms: an oral tablet (sold as ReVia) and an injection (sold as Vivitrol). The tablet produces a short-term barrier effect that only lasts for a few hours. However, the injection gradually releases naltrexone into the bloodstream and provides a continuing barrier effect that remains active for about 30 days. In the context of alcoholism, specific benefits of ReVia or Vivitrol use include a reduction in the pleasure produced by drinking and a reduction in the intensity of the cravings that promote continued alcohol intake.
Which Factors Have an Impact?
In the study review published in Addiction, researchers from the University of North Carolina at Chapel Hill and RTI International used an analysis of 20 previous studies to determine if any specific factors make it more or less likely that naltrexone will produce desirable alcoholism treatment results in a given individual. All of the studies under consideration were conducted between 1990 and early 2012. Specific factors examined included the demographic backgrounds of people receiving the medication (age, gender, education, income, racial/ethnic background, etc.), as well as various details of genetics and biology. The researchers examined each potential factor in detail and weighed its potential influence on the effectiveness of naltrexone.
At the end of their analysis, the researchers concluded that there is varying evidence to support the impact of several factors on the usefulness of naltrexone. The most significant evidence indicates an increased treatment benefit for people who have a history of serious alcohol-related issues in their family bloodlines, as well as for people who have a specific gene variation that alters the level of brain access provided by the opioid receptors. Other factors with some supporting evidence as a positive or negative influence on the alcohol-related effectiveness of naltrexone include having relatively severe alcohol cravings, being male and the level of alcohol intake maintained before seeking treatment.
The study’s authors note that researchers are still learning how to identify alcoholism patients who have a positive response to naltrexone treatment. In addition, they note that there is some concern about the overall quality of the previously published studies that examined the factors capable of altering the medication’s effectiveness. Although current evidence provides some support for the role of genetic susceptibility and alcohol-related family background, the authors believe that the research community still does not have enough information to help doctors decide which alcoholism-affected individuals will benefit least and most from naltrexone use.
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