New Treatment Blocks the Addictive Effects of Opioid Drugs

New Treatment Blocks the Addictive Effects of Opioid Drugs

New Treatment Blocks the Addictive Effects of Opioid Drugs

New Treatment Blocks the Addictive Effects of Opioid DrugsOpioids (also known as narcotics or opiates) are a group of natural and synthetic drugs that produce euphoria and block the sensation of pain by altering normal function in parts of the body that include the brain and spinal cord. Unfortunately, because of specific changes they make in the brain, both legal and illegal opioids are frequent subjects of drug abuse and drug addiction. In 2012, researchers from Australia’s University of Adelaide discovered that a medication—called (+)-naloxone or plus-naloxone—can potentially block the addictive effects of opioid drugs while still permitting the beneficial pain-relieving effects of morphine and other narcotic medications.

Opioid Basics

All natural and synthetic opioid drugs have their origins in the chemical structure of mind-altering substances found in Papaver somniferum, a plant better known as the opium poppy. Three separate opioids—morphine, opium, and codeine—come directly from sap produced by this poppy during a specific stage of its growth cycle. Several other substances—Including heroin, hydrocodone, and oxycodone—come from the chemical manipulation of naturally occurring opioids. In addition, pharmaceutical manufacturers use the chemical blueprint of naturally occurring opioids to make completely synthetic narcotic substances such as meperidine, morphine, fentanyl, and synthetic codeine. While certain opioids are illegal, many others have such value as pain-relievers that doctors prescribe them in a controlled medical setting despite the risks they pose for abuse and addiction.

Inside the brain and spinal cord (also known as the central nervous system), opioids produce their primary euphoric and painkilling effects by accessing sites known as opioid receptors, which provide entry into the interiors of nerve cells called neurons. In the absence of opioids, the body uses these receptors to provide neuron access for a number of substances—including well-known chemicals called endorphins and lesser-known chemicals called dynorphins and enkephalins—that produce natural pain relief and boost mental well-being. In the presence of opioids, the opioid receptors greatly increase the brain’s supplies of a chemical called dopamine, which activates a pleasure/reward pathway inside the brain known as the limbic system. Addiction to opioids typically occurs when users start to rely on and crave the euphoric, rewarding effects associated with high levels of dopamine inside this system.

According to the findings of the researchers from the University of Adelaide, reported in 2012 in the “Journal of Neuroscience,” opioid molecules also attach themselves to specialized receptors in the body called troll-like receptor 4 (TLR4) receptors. Under normal circumstances, these receptors function as part of the immune system by alerting the body to the presence of certain types of invading bacteria. However, when opioids exert their effects, TLR4 receptors essentially function as drug amplifiers that dramatically increase opioids’ power to produce addiction.

Effects of Plus-Naloxone

Plus-naloxone is a non-opioid medication related to naloxone, a drug doctors use in emergency circumstances to reverse the effects of an opioid overdose. When introduced into the body, plus-naloxone effectively shuts down activity in the TLR4 receptors, the authors of the study in the Journal of Neuroscience report. As a result, rats given the medication in laboratory testing experience significantly smaller dopamine increases in their brains when later exposed to the opioid morphine. They also exhibit a greatly reduced response to the rewarding effects of morphine; in turn, this reduced response essentially severs the connection between morphine use and addiction. At the same time, rats given plus-naloxone continue to experience the pain-relieving benefits associated with morphine use. These results mark the first time that any researchers have successfully separated the addictive qualities of an opioid drug from its beneficial drug effects.

Considerations

As noted, the University of Adelaide study was performed on rats, not human beings. This type of animal testing is a common practice used in the earlier stages of drug/medication development as a way to make important assessments before human subjects become involved. The authors of the study note that, before they can consider using human test subjects, they must first make more detailed observations regarding the TLR4 receptors’ role in producing opioid addiction. If they are ultimately successful, their findings may prove valid for a range of legal, therapeutically useful opioids other than morphine. In addition, addiction specialists may be able to add plus-naloxone to the arsenal of treatments available to combat the effects of illegal, therapeutically useless opioids such as heroin and opium. At the earliest, human trials for plus-naloxone would probably begin sometime in 2014.

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