Stanford (Calif.) University School of Medicine researchers studied the cause of opioid side effects, according to Medical Xpress.
The researchers sought to identify the source of two opioid side effects — "a growing tolerance and a paradoxical increased sensitivity to pain," according to Medical Xpress. As a result of these side effects, patients often take higher doses of opioids to experience pain relief. In turn, patients up their addiction risk and respiratory failure.
Nature Medicine published the study.
Here are five insights:
1. In mouse models, the researchers discovered opioids' impact on peripheral pain neurons in the body (not in the spinal cord or brain), may result in tolerance and increased pain sensitivity.
2. The study also refuted the theory that microglia (non-neuronal in the spinal cord and brain) cause opioids' side effects. The researchers argue microglia do not possess the gene necessary for forming the receptors that cause the side effects.
3. The researchers used a drug to block opioids' effects on the periphery. This drug successfully eradicated the side effects without disturbing opioids ability to reduce pain.
4. Researchers used FDA-approved methylnaltrexone bromide to block the side effects, which is already in use to reduce constipation.
5. Researchers noted future clinical trials are necessary to test their theory in humans.