03 Jun Researchers Introduce New Medications to Treat Drug Addiction, Alcoholism
Researchers unveiled the first opioid-blocking, extended-release injectable suspension naltrexone (XR NTX) at the 2010 American Psychiatric Association (APA) Annual Meeting held from May 22–26, 2010 in New Orleans. The pharmaceutical company Alkermes, Inc. discussed new data on XR NTX gathered from company-sponsored studies that revealed its significant potential for combating alcohol and opioid addiction. Alkermes recently submitted a supplemental New Drug Application (sNDA) to the U.S. Food and Drug Administration (FDA) for approval of XR NTX’s commercial use in the treatment of opioid dependence. Currently, XR NTX is commercially available for the treatment of alcohol dependence as the once-daily pill Vivitrol® by Alkermes since being approved by the FDA in 2006. If the injectable form of XR NTX gains approval, it will become the first non-addictive, non-narcotic drug agent available in a once-monthly prescription.
During the meeting, Director of the National Institute on Drug Abuse (NIDA), Dr. Nora Volkow, encouraged researchers to approach their studies on the treatment for addiction by investigating the underlying brain circuitry that allows the potential for relapse in substance abusers. Four critical investigations at the meeting presented data on the benefits and potential of XR NTX, including suppressing alcohol and heroin cravings. XR NTX helps block opioid receptors in the brain, thereby reducing the craving for alcohol or opioids. XR NTX combats addiction by working on a biological level as it changes brain circuitry and responses to cues, rather than temporarily repressing the need to drink or smoke.
In the study led by McLean Hospital’s Brain Imaging Center, researcher Dr. Scott Lukas and his team used brain imaging to map the effects of XR NTX overtime as alcohol addicts were exposed to vulnerable situations. The investigation included 28 participating alcoholics, of which 15 were given the XR NTX injection while 13 were given a placebo shot. A BOLD (Blood Oxygen Level Dependent) fMRI scan documented the participants’ brain activity as they were exposed to pictures of alcoholic beverages and odors of their preferred alcoholic beverage. While all participants reported feeling immediate cravings for alcohol, only the individuals with the XR NTX reported the cravings subsiding after a few minutes and returning to normal levels. MRI scans taken over a two-week period revealed a disparity among the two groups’ brain activities. Scans of those with the placebo injections showed no variation in brain blood-flow activation after two weeks, and cravings remained peaked. Those with the XR NTX injections showed considerable reductions in brain blood-flow activity in areas that control the reward system, cognition, and emotions. The study concluded that the medication successfully caused lower response to alcohol cues in alcohol-dependent individuals.
In a second study, conducted by St. Petersburg Regional Center for Addictions in Russia, researcher Dr. Evgeny M. Krupitsky and his team concluded that XR NTX injections also reduced cravings in opioid-dependent individuals. After a 24-week investigation that involved 250 participants who had an opioid addiction spanning ten years, the XR NTX injection group showed significant reductions in their cravings, compared to the controlled group that received placebo injections who showed no change in craving levels. The XR NTX group also displayed improvements in such secondary factors as less self-reported opioid use, less physiologic dependence, and better retention. XR NTX helped eliminate addict’s overactive reward system in their brains that had conditioned them to continue their heroin use, and enabled them to sustain abstinence and prevent relapse.
Researchers at the annual meeting also discussed the potential use of other medications in addiction therapy. Modafinil, currently used to treat narcolepsy by preventing sudden sleep attacks, may also facilitate abstinence for cocaine addicts. Bupropion (amfebutamone), an older antidepressant that is already applied to smoking cessation therapy, is now being considered for treating methamphetamine addiction.
Addiction is now understood as a brain disorder, like other mental illnesses, in which dysfunctioning brain circuitry disrupts normal brain communication. When an illicit substance such as opium or alcohol is absorbed into the central nervous system, it causes increased activity in the brain’s neurotransmission of dopamine, known as the ‘reward system,’ creating a sense of euphoria. Substance use causes lasting changes in the brain cells as the brain and body both adjust to accept the presence of the substance in the system. Opium and alcohol can both serve as an agonist to the GABA receptors, making the brain build a dependency on their presence. When there is a lack of the substance in the body system, withdrawal symptoms occur, and dependency worsens. Habitual substance abusers develop tolerances to the substance and must take higher quantities in order to generate the same intoxicating effects. This reaction occurs due to miscommunication among fractured circuits in multiple regions in the brain. Under such neurological conditions, substance abusers become vulnerable to their cravings, which also explains why many experience relapse after undergoing treatment. While the research teams caution that XR NTX may not be an absolute cure to alcoholism or opiate addiction, the benefits of this new injectable give addiction therapists and physicians more options when it comes to treating such complex and multifaceted substance abuse disorders.
Considering the brain’s circuitry in substance abuse disorders helps explain their relation to other mental illnesses such as depression, post-traumatic stress disorder, and schizophrenia—and why these diseases are often comorbid. Dysfunctions occurring in the addict’s brain are analogous to brain patterns that occur in several mental disorders. Addicts display symptoms similar to other mental illnesses such as irritability, mood changes, impulsivity, and compulsivity. If pharmaceutical agents are proving successful in the treatment of certain mental illnesses, they may also have potential in treating addiction disorders. These new studies open the door to growth opportunities in addiction treatment and therapy. The FDA will announce its decision regarding the injectable formulation of XR NTX on October 12, 2010.
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