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A new study by an international team of scientists claims that morphine and heroin addiction can be blocked while increasing pain relief in opiate dependent patients.

Researchers from the University of Adelaide and University of Colorado discovered the key mechanism in the body's immune system that is responsible for amplifying the addiction to opioid drugs, reported Medical Xpress.

The drug, (+)-naloxone (pronounced: PLUS nal-OX-own) can selectively block the immune-addiction response, study has shown.

The results of the study that has lead to the discovery of new co-formulated drugs which can help people with severe pain, and help heroin addicts kick the habit, were published in the Journal of Neuroscience. 

"Our studies have shown conclusively that we can block addiction via the immune system of the brain, without targeting the brain's wiring," says lead author of the study, Dr Mark Hutchinson, ARC Research Fellow in the University of Adelaide's School of Medical Sciences. 

"Both the central nervous system and the immune system play important roles in creating addiction, but our studies have shown we only need to block the immune response in the brain to prevent cravings for opioid drugs." 

According to Hutchinson the discovery is a paradigm shift on "how we think about drug action in the brain and how we think about drug addiction".

The researchers concentrated their work towards the immune receptor known as Toll-Like receptor 4 (TLR4). 

"Opioid drugs such as morphine and heroin bind to TLR4 in a similar way to the normal immune response to bacteria. The problem is that TLR4 then acts as an amplifier for addiction," Hutchinson says. 

"The drug (+)-naloxone automatically shuts down the addiction. It shuts down the need to take opioids, it cuts out behaviors associated with addiction, and the neurochemistry in the brain changes - dopamine, which is the chemical important for providing that sense of 'reward' from the drug, is no longer produced." 

"This work fundamentally changes what we understand about opioids, reward and addiction. We've suspected for some years that TLR4 may be the key to blocking opioid addiction, but now we have the proof. The drug that we've used to block addiction, (+)-naloxone, is a non-opioid mirror image drug that was created by Dr Kenner Rice in the 1970s. We believe this will prove extremely useful as a co-formulated drug with morphine, so that patients who require relief for severe pain will not become addicted but still receive pain relief. This has the potential to lead to major advances in patient and palliative care," senior author Professor Linda Watkins, from the Center for Neuroscience at the University of Colorado Boulder says.

Opioid drugs such as morphine are known to target opioid receptors in the central nervous system, which block pain signals to the brain and flood it with the "feel-good" chemical dopamine. This reward response is what makes opioids so addictive, says New Scientist.

Morphine is used pain killer but its addictiveness restricts its usage with caution.

According to researchers, a clinical trial may be possible within the next 18 months.