Nasal Spray May Provide Opioid Pain Relief Without Dependency

By Paul Gaita 02/08/18

Experiments on mice indicated that the animals experienced pain relief but displayed no signs of tolerance.

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nasal spray

Scientists in the United Kingdom say they have developed a nasal spray that delivers a natural pain-relieving opioid without the debilitating side effects, including dependency.

The spray features millions of nano-particles containing a class of opioids found in the body called enkephalins, which in tests involving rats produced pain relief without developing a craving for the opioids, which scientists believe could reduce issues of dependency and overdose. Should tests on humans prove positive, the study authors and other medical professionals hope that the spray could provide a safe, fast-acting alternative for prescription pain medication like morphine or fentanyl, said to be among the root causes of the global opioid epidemic.

Scientists have hoped that natural opioids like enkephalins could provide pain relief, especially in cases involving severe or breakthrough pain like bone cancer, which is often treated with synthetic opioids. But pain treatment based on enkephalin faces two significant hurdles after being introduced to the body: they break down quickly after being injected into the bloodstream, and they cannot cross the blood-brain barrier, a semi-permeable membrane which filters out substances in the blood which it perceives to be injurious to the brain.

But scientists at University College London circumvented these issues by encasing the enkephalin in soluble polymer nanoparticles, which protected the natural opioids while passing through the blood-brain barrier. Once absorbed into the area of the brain that deals with pain perception, the particles dissolved at a slow but steady rate, delivering consistent relief, and passed the polymer casing through the body.

The results of their tests on laboratory mice and rats, which was published in the January 2018 edition of the Journal of Controlled Release, showed that by injecting the enkephalin, known as NM0127, directly into the brains of test subjects, the animals experienced pain relief but displayed no signs of tolerance.

Previous tests on mice also showed that subjects that were tolerant to morphine also received the pain relief benefits. Additionally, the tests involving rats found that none of the animals sought out the drug as a reward, which appeared to indicate that NM0127 did not produce cravings.

The scientists concluded that more tests would be required to definitively determine if the natural opioid was free of tolerance or dependency issues before testing can begin on human subjects. If those tests—which will involve delivery of the opioid through a nasal spray to see if it reduces the pain of immersing an arm in ice-cold water—prove successful, the scientists next hope to apply the spray to bone cancer patients who experience sudden breakthrough pain.

Lesley Colvin, a professor of pain medicine at Western General Hospital in Edinburgh, Scotland, says that the time required for prescription painkillers like fentanyl to take effect—which is usually about 10 to 20 minutes—would necessitate a more fast-acting approach in cases involving breakthrough pain.

"There is a need for something with a very fast onset when pain is there," she noted to the Guardian. "That would be a huge advantage."

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Paul Gaita lives in Los Angeles. He has contributed to the Los Angeles Times, Variety, LA Weekly, Amazon.com and The Los Angeles Beat, among many other publications and websites. 

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