Sinomenine is an alkaloid found in the root of the climbing plant Sinomenium acutum which is native to Japan and China. It is traditionally used in herbal medicine in these countries, as a treatment for rheumatism and arthritis.However, its analgesic action against other kinds of pain is limited. Sinomenine is a morphinan derivative, related to opioids such as levorphanol and the non-opioid cough suppressant dextromethorphan. Its anti-rheumatic effects are thought to be primarily mediated via release of histamine, but other effects such as inhibition of prostaglandin, leukotriene and nitric oxide synthesis may also be involved. Sinomenine is a unique plant alkaloid, as it potently releases histamine in association with degranulation of tissue mast cells in mammalian tissues. This action occurs preferentially in the skin and joint capsules.
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