Morphine, pharmacological action substitutes

A number of in vivo pharmacological studies reported that amino acid substitution in position 6 of 14-O-methyloxymorphone (48) afforded derivatives 55-60 that produce potent antinociceptive actions via peripheral mechanisms after s.c. administration in different pain models such as acute nociception i.e. tail-flick test [68], inflammatory pain i.e. formalin test [68] and carrageenan-induced hindpaw inflammation [75] and visceral pain i.e. acetic acid-induced writhing test [93]. In the tail-flick test in the rat, the 6-amino acid derivatives were 19- to 209-fold more potent than morphine (Table 7) and showed similar potency to fentanyl after s.c... 

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