. 2004 Dec 13;144(6):875–884. doi: 10.1038/sj.bjp.0706045

Table 2.

Theoretical Z_add and experimental Z_mix ED₅₀ antinociceptive values obtained from the three drug combinations (s.c.) in the hot plate and tail flick assays

	Hot plate assay			Tail flick assay
Drug combination	Z_add	Z_mix	n	Z_add	Z_mix	n
CP55,940+dexmedetomidine	0.598	0.223^*	52	0.266	0.324	38
CP55,940+morphine	15.3	7.54^*	57	5.91	3.31^*	45
Dexmedetomidine+morphine	14.7	16.7	65	5.66	6.97	41

n: number of mice. Each combination was a 1 : 1 fixed ratio of the respective ED₅₀ of drug A : ED₅₀ of drug B. Z_add: theoretical dose required for a purely additive interaction; Z_mix: experimental value determined from the combination dose–response curve (see Methods).

Statistically significant synergistic or supra-additive interaction (P<0.05).