. Author manuscript; available in PMC: 2012 Sep 1.

Published in final edited form as: Behav Pharmacol. 2011 Sep;22(5-6):548–557. doi: 10.1097/FBP.0b013e328349ab0d

Table 4. Relative antinociceptive potency of morphine and ED₅₀ potency ratios for a morphine control group (no chronic treatment) compared to groups following chronic administration of various dose ratios of d:l-methadone as assessed in the WWTW procedure.

Dosing condition	Morphine ED₅₀ mg/kg (95% CL) at 50°	ED₅₀ potency ratio (95% CL)	Morphine ED₅₀ mg/kg (95% CL) at 55°	ED₅₀ potency ratio (95% CL)
Morphine control	1.25 (0.66–2.37)	–	5.13 (4.05–6.51)	–
0:1	6.87^a (5.13–9.19)	4.44 (1.90–10.28)	15.18^a (13.02–17.69)	2.84 (2.14–3.75)
1:1	3.27^a (1.97–5.41)	2.45 (1.04–5.63)	10.05^a (7.98–12.67)	1.94 (1.31–2.84)
3:1	1.31 (0.67–2.56)	1.18 (0.44–3.01)	9.39 (3.65–24.19)	2.05 (0.64–3.88)
6:1	2.00 (1.02–3.93)	1.59 (0.64–4.50)	3.98 (2.55–6.20)	0.83 (0.45–1.52)
10:1	2.12 (1.80–2.49)	1.68 (0.99–3.02)	5.21 (4.43–6.12)	1.04 (0.79–1.39)
6:0	1.09 (0.92–1.29)	0.87 (0.48–1.71)	3.98 (3.43–4.61)	0.81 (0.61–1.08)

CL, confidence limits.

Significantly different from morphine control at P< 0.05.

Table 4. Relative antinociceptive potency of morphine and ED50 potency ratios for a morphine control group (no chronic treatment) compared to groups following chronic administration of various dose ratios of d:l-methadone as assessed in the WWTW procedure.