. Author manuscript; available in PMC: 2010 Jan 5.

Published in final edited form as: Eur J Pharmacol. 2008 Nov 11;602(1):92–100. doi: 10.1016/j.ejphar.2008.11.004

Table 1.

ED50 values in mg/kg (95%CL) for fentanyl and a delta opioid administered alone or as part of a mixture in the assay of schedule-controlled responding. ^abIndicates ED50 confidence limits for fentanyl or delta opioid in mixture do not overlap with ED50 confidence limits for fentanyl or delta opioid alone. ^aED50 in mixture lower than ED50 for drug alone. ^bED50 in mixture higher than drug alone.

	Fentanyl	Delta Opioid
Treatment	ED50 (95%CL)	ED50 (95%CL)

Fentanyl Alone	0.023 (0.012-0.045)
SNC243A Alone		0.35 (0.18-0.68)
5:1 SNC/Fent	0.019 (0.009-0.041)	0.09 (0.04-0.20)
15:1 SNC/Fent	0.018 (0.010-0.033)	0.27 (0.15-0.49)
45:1 SNC/Fent	0.007 (0.004-0.015)	0.34 (0.11-0.17)
Fentanyl Alone	0.019 (0.013-0.027)
MSF61 Alone		>10 mg/kg
30:1 MSF/Fent	0.013 (0.009-0.020)	0.39 (0.26-0.59) ^a
89:1 MSF/Fent	0.010 (0.007-0.012) ^a	0.87 (0.69-1.10) ^a
267:1 MSF/Fent	0.015 (0.010-0.021)	3.93 (2.74-5.64) ^a
Fentanyl Alone	0.019 (0.013-0.027)
Naltrindole Alone		>10 mg/kg
4:1 NTI/Fent	0.007 (0.001-0.014)	0.030 (0.016-0.054) ^a
12:1 NTI/Fent	0.011 (0.007-0.018)	0.134 (0.086-0.210) ^a
36:1 NTI/Fent	>0.056^b	>2.0