Table 2. Antinociceptive Potencies in the Tail-Flick Test in the Rat after sc Administration.

	ED50 (nmol/kg, sc), 95% CLa time after drug administration
compd	0.5 h	1 h	2 h	3 h	relative potencyb morphine = 1
morphine	6053c	7626	13285		1
	(4037−9080)	(5084−11439)	(8856−19929)
9d	137	58.5c	143	437	103
	(85.7−219)	(36.5−93.7)	(86.8−237)	(243−786)
10d	50.8	29.0c	43.3		209
	(32.7−78.7)	(18.8−44.9)	(27.9−67.1)
11	63.5	58.3c	84.0	148	104
	(15.4−262)	(18.0−188)	(31.4−255)	(28.4−775)
12	164	92.3c	124	189	66
	(78.6−341)	(39.5−215)	(53.0−292)	(69.8−514)
13	127	81.1c	87.9	116	75
	(65.0−246)	(46.4−139)	(43.9−176)	(48.5−278)
14	180	143	130c	192	47
	(122−247)	(85.8−238)	(73.4−231)	(90.0−414)
15	365	348c	363	427	17
	(195−687)	(212−570)	(215−615)	(205−692)
16	33.8	26.8c	34.4	56.0	226
	(18.8−60.5)	(14.1−51.0)	(17.7−66.8)	(21.9−143)
17	1388	349c	433	543	17
	(117−16526)	(113−1072)	(172−1084)	(180−1636)
18	1561	183	147c	−e	41
	(199−12223)	(17.7−1877)	(13.9−1554)

^aValues in paranthesis are 95% confidence limits.

^bRelative potencies were calculated at the peak of action.

^cPeak of effect.

^dFrom ref (31).

^e−: no dose−response relationship.