Development of 5-Substituted N-Methylmorphinan-6-ones as Potent Opioid Analgesics with Improved Side-Effect Profile

Table 4

Comparison of antinociceptive potencies of 14-methoxymetopon (13) and its 14-phenylpropoxy substituted analogues 20 and 21, with morphine and etorphine.

	ED50 (μg/kg)^a
	Hot-plate test	Tail-flick test	PPQ writhing test
20	2.6	4.4	1.7
21	0.10	0.08	0.16
13	30	30	9.0
Morphine	850	1,920	400
Etorphine	1.0	2.0	0.40

^aDetermined in mice after s.c. administration [22].