Morphine and the other alkaloids found in the opium poppy plant still represent the preferred
therapeutic tools to treat severe pain in first aid protocols, as well as chronic pain. The use of
the opiate alkaloids is accompanied by several unwanted side effects; additionally, some forms of pain
are resistant to standard treatments (e.g. neuropathic pain from cancer). For these reasons, there is currently
renewed interest in the design and assay of modified versions of the potent endogenous opioid
peptides endomorphin-1 and endomorphin-2. This review presents a selection of the strategies directed
at preparing highly stable peptidomimetics of the endomorphins, and of the strategies aimed at improving central
nervous system bioavailability, for which increased in vivo antinociceptive efficacy was clearly demonstrated.
Keywords: Blood brain barrier, Endomorphins, Enzymatic stability, Lipophilicity, Opioid, Peptidomimetic.
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