Why do oxycodone make you itch

This leads to powerful pain relief, although scientists do not know exactly why. Louis showed that only one opioid receptor isoform is responsible for itching—and it is not involved in pain. Mice bred to have fewer of these particular receptors did not scratch themselves when given an opioid, but they did exhibit the telltale mouse signs of pain relief, such as less flinching when researchers flicked their tails. Now that scientists know that pain relief and itching can be decoupled, they will try to make itch-free opioid drugs a reality.

Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. The opiate-associated itch is so common that even women who get epidurals for labor pain often complain of itching.

For many years, scientists have scratched their own heads about why drugs that so effectively suppress pain also induce itch. Louis have shown they can control opioid-induced itching without interfering with a drug's ability to relieve pain. The discovery raises tantalizing possibilities for new treatments to eliminate itch in cancer and surgery patients as well as others who rely on opioids to relieve chronic and severe pain.

By identifying and blocking a specific variant of the opioid receptor in the spinal cord, Zhou-Feng Chen, PhD, director of Washington University's Center for the Study of Itch, a newly established multidisciplinary center aimed at translating basic itch research into novel treatments, and his colleagues have demonstrated for the first time that it is possible to inhibit itch without dulling morphine's pain-killing effects.

When we blocked MOR1D, mice that got morphine no longer needed to scratch, and they still received the same level of pain relief. In previous studies, Chen, a professor of anesthesiology, of psychiatry and of developmental biology, had identified an itch-specific receptor in the spinal cord called GRPR gastrin-releasing peptide receptor. His studies also have shown that neurons containing GRPR specifically transmit itch but do not carry pain information.

In a surprising twist, first author Xian-Yu Liu, PhD, a postdoctoral researcher in Chen's lab, found that a major variant of the opioid receptor called MOR1 exclusively mediates morphine's analgesic effects in the spinal cord. When he blocked MOR1D, the mice no longer scratched. When he blocked MOR1, the animals no longer received the drug's pain-killing benefits, but they continued to scratch. It only transmits itch.

In mice treated with morphine, the investigators were able to eliminate itching without affecting pain relief. Because humans have similar morphine receptors in the brain and the spinal cord, the researchers believe this new finding may someday make it possible to treat itching in those patients who take opioid drugs to relieve pain.

One of the very peculiar, interesting side effects is itching. Opioid-induced itching while suppressing pain sensation has been one of the mysteries for a long, long time. We found that this isoform is specifically required for relaying morphine-induced itch.