NE-19550: a novel, orally active anti-inflammatory analgesic

NE-19550, N-(3-methoxy-4-hydroxybenzyl)oleamide, is a capsaicin analogue that has been shown to possess oral activity in the 55 degrees C rat hot-plate and mouse phenylquinone abdominal constriction analgesia tests. The compound also displayed anti-inflammatory activity orally in the carrageenan-inflamed rat-paw test and topically in the croton oil-inflamed mouse-ear test. NE-19550 activity in the thermal analgesia assay was not blocked by the opioid antagonist naloxone, and no inhibition of prostanoid synthesis in rat platelets or tissues was seen following a high analgesic and anti-inflammatory oral dose (300 mg/kg). A wide variety of known neuronal antagonists (adrenergic, serotonergic, dopaminergic, cholinergic, GABA-ergic, histaminergic) were found not to inhibit NE-19550 analgesia, further indicating a lack of involvement of known drug receptors mediating analgesic responses. Analgesic doses of NE-19550 were also found to lack the acute toxicity and thermoregulatory desensitization characteristics of the parent natural product capsaicin. It appears to represent a new class of potent-acting, non-narcotic, anti-inflammatory analgesic agents.