KR-25018: A novel, orally active analgesic with non-narcotic properties
Among the new series of phenylacetamides, one of capsaicin derivatives, KR-25018 was found to have a very potent analgesic activity. Thus, the pharmacological properties of KR-25018 were compared with those of morphine, capsaicin, and nonsteroidal antiinflammatory drugs (NSAIDs). The analgesic activities were evaluated in several animal models, using different stimuli, such as phenylbenzoquinone(PBQ)-induced writhing test, tail-flick test in mice and adjuvant arthritic flexion test in rat. The relationship of pharmacological properties of KR-25018 to that of centrally acting opioids was assessed by the blocking test using naloxone. The analgesic potency of the KR-25018 (MPED50=0.89 p.o. in PBQ-induced writhing test, MPED50 =0.61 s.c. in tail-flick test in mice), with different action mechanism from morphine and NSAIDs, was comparable to that of morphine.
Key wordsCapsaicin KR-25018 Morphine NSAIDs Analgesic activity
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