Morphine antagonist actions

Pharmacology Nalbuphine is a potent analgesic with narcotic agonist and antagonist actions. Its analgesic potency is essentially equivalent to that of morphine on a milligram basis. 

Blane G.F. and Boura A.L. Analgesic and other actions of morphine antagonists, Naunyn Schmiedebergs Arch. Exp. Pathol. Pharmakol. 1968, 259, 154-155. 

A considerable extension of the duration of activity together with a strongly reduced toxicity has been found (79) for a preparation with morphine-antagonistic activity [7 7 the place of its action being localized also in the central nervous system. Hie possibility of cleavage is in this case attributed to the activated ester, bound between the polymeric chain and the active substance. Besides the above-mentioned derivative of acrylic acid a derivative of vinyl carbamate has also been applied. 

Unfortunately, in a series such as this, antagonists have not yet been discovered with the potency to match agonists. Diprenorphine is about 100 x nalorphine as a morphine antagonist, and it exhibits no antinociceptive properties in the MW test. 339 However, in the GPI assay, some agonist actions were... 

Morphine-3-glucuronide (261) and the corresponding 3-sulfate had no MHP, sc, or ic activity, and morphine-3-phosphate and morphine-6-phosphate were similar to morphine in their responses. These activities were reflected in increased agonist potencies (MW, 3 x nalorphine) seen for nalorphine-6-glucuronide and -6-sulfate, with a maintenance of antagonist actions. 

Butorphanol is a narcotic agonist with analgesic action hve times more potent than morphine, and a narcotic antagonist with antagonist action 1/40 that of naloxone. Butorphanol... 

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