. 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 2.

Predicted Zadd and experimentally determined Zmix values (95%CL) for mixtures of fentanyl and a delta opioid in the assay of schedule-controlled responding. ^abIndicates Zmix confidence limits do not overlap with Zadd confidence limits. ^aZmix lower than Zadd (superadditivity). ^bZmix higher than Zadd (subadditivity).

Mixture	Zadd (95%CL)	Zmix (95%CL)

5:1 SNC243A/Fentanyl	0.11 (0.06-0.20)	0.11 (0.05-0.25)
15:1 SNC243A/Fentanyl	0.19 (0.10-0.36)	0.29 (0.16-0.53)
45:1 SNC243A/Fentanyl	0.27 (0.14-0.52)	0.34 (0.18-0.67)
30:1 MSF61/Fentanyl	0.58 (0.40-0.84)	0.41 (0.27-0.61)
89:1 MSF61/Fentanyl	1.67 (1.15-2.42)	0.88 (0.70-1.11) ^a
267:1 MSF61/Fentanyl	4.96 (3.42-7.19)	3.95 (2.75-5.67)
4:1 NTI/Fentanyl	0.09 (0.06-0.14)	0.04 (0.02-0.07)
12:1 NTI/Fentanyl	0.24 (0.17-0.35)	0.15 (0.09-0.23)
36:1 NTI/Fentanyl	0.69 (0.47-1.0)	>2.1^b