Nearly one third of the world's adult population suffers with the pain of arthritis. While NSAIDs and COX-2 inhibitors offer the promise of relief, these drugs also bring the risk of adverse effects, from stomach ulcers to heart attack.
Recent studies have suggested the potential of tapping into the body's supply of painkilling peptides as a safe, natural approach to arthritis pain management. Extraneous substances such as morphine can be disadvantageous in arthritis pain therapy due to a large number of adverse side-effects associated with these compounds. In addition, the lack of selectivity of morphine means that precise targeting of u-opioid receptors to control chronic pain has proven to be problematic. What's more, several clinical and experimental studies of m-opioid therapy have shown ambiguous results. The recent discovery of a natural morphine-like compound in joints called endomorphin 1 could circumvent these therapeutic drawbacks due to its greater selectivity for the u-opioid receptor. Endomorphin 1 has the potential, therefore, to be a major painkilling agent in the body with less chance of risk.
Researchers at the University of Calgary set out to determine the effectiveness of endomorphin 1, with a painkilling capacity equal to or greater than morphine – on knee joint pain. Their subjects were male rats with induced arthritis, both acute and chronic. Their findings, featured in the October 2005 issue of Arthritis & Rheumatism, shed light on why u-opioid therapy may not work to control long-term arthritis pain.