Rising Opioid Overdose Deaths Prompt Need for New Painkillers

Opioid Crisis Statistics

The increasing number of deaths from opioid overdoses has underscored the urgent need for alternative pain management solutions. In Canada in 2017, approximately 17 individuals were hospitalized daily due to opioid-related incidents. Similarly, the United States experiences over 115 daily fatalities linked to opioid overdoses. This crisis, fueled by the misuse of morphine and other opioids, necessitates the development of new painkillers with a lower potential for addiction.

The Global Challenge of Pain Management

Pain management presents a significant challenge worldwide. Individuals suffering from chronic pain often endure distress due to inadequate treatment, which also affects the broader community. Traditional opioids, including morphine, carry the risk of side effects and high potential for abuse. A novel, effective painkiller that can specifically target painful areas in the body may address these ongoing issues.

Enkephalin: A Natural Pain Relief Protein

Mechanism of Action

Enkephalin is a naturally occurring protein in the body that alleviates pain by activating opioid receptors, similarly to morphine. However, while morphine binds to both mu and delta receptors, enkephalin predominantly interacts with the delta receptor, which is associated with a reduced risk of abuse and fewer side effects.

Challenges in Developing Injectable Protein Painkillers

Developing injectable protein-based painkillers poses significant challenges, primarily due to the instability of proteins in the bloodstream. Researchers are currently exploring two strategies: binding proteins to neutral molecules to enhance their stability and utilizing nanoparticle technology.

Recent Research on a New Painkiller

Study Overview

Researchers at the Institut Galien Paris-Sud in France have developed a new painkiller using nanoparticle technology, tested on a rat model of inflammation. Their findings were published in the journal *Science Advances*.

Creation of Enkephalin-Squalene Molecules

The research involved creating three distinct painkiller molecules, each consisting of enkephalin linked to squalene, a stabilizing molecule. Squalene was attached to enkephalin at three different sites to enhance stability in the bloodstream. The enkephalin-squalene compounds were then converted into nanoparticles to protect them from enzymatic degradation.

In Vitro Testing

Initial tests of the enkephalin-squalene molecules were conducted in vitro to assess their ability to detach from the squalene group in serum samples. Results indicated that two of the molecules released enkephalin at varying rates, influenced by the attachment site of the squalene group.

In Vivo Pain Relief Evaluation

Subsequently, the researchers evaluated the pain-relief effects of these molecules in a rat model with inflammation induced by carrageenan. They applied heat to the inflamed paw before and after administering a placebo, morphine, and the enkephalin-squalene molecules, monitoring the rats’ responses.

Findings on Pain Relief Duration and Targeting

Long-Lasting Pain Relief

All rats that received morphine and the enkephalin-squalene molecules experienced reduced pain sensitivity from heat application. Notably, the pain relief from the enkephalin-squalene compound persisted longer than that provided by morphine.

Targeting Inflammation

Following the injection of the enkephalin-squalene molecule, researchers collected tissue samples and employed fluorescence studies to visualize the molecule’s targets. The data indicated that the compound concentrated in the inflamed tissue of the paw rather than in the central nervous system.

Future Directions for Research

In conclusion, the combination of nanoparticle technology and the attachment of squalene to the new painkiller facilitated prolonged pain relief in localized inflamed tissues in rats. The limited penetration of this painkiller into the brain and spinal cord suggests a potential reduction in side effects. Further studies are necessary to explore the impact of varying doses, injection frequencies, and timings on the pain relief efficacy in animal models.

References

Feng J, Lepetre-Mouelhi S, Gautier A, et al. A new painkiller nanomedicine to bypass the blood-brain barrier and the use of morphine. Sci Adv. 2019.
Canadian Mental Health Association. Overdose prevention. https://cmha.ca/documents/overdose-prevention