Table 1.

Results from locomotor activity tests.

#	Drug	Maximum effect (distance traveled in cm ± SEM)	Maximum effect as a % of fentanyl’s maximum effect	Estimated dose (mg/kg) required to elicit 100 m of travel
1	Morphine	22,381 ± 3785	64.1 ± 10.8	15.3
2	Fentanyl	34,905 ± 5355	100 ± 15.3	0.23
3	Beta-methylfentanyl	20,165 ± 5413	57.8 ± 15.5	1.74
4	Para-methylfentanyl	1555 ± 632	4.46 ± 1.81	N/A
5	Para-methoxyfentanyl	13,109 ± 4412	37.6 ± 12.6	3.63
6	Fentanyl carbamate	13,107 ± 5250	37.6 ± 15.0	72.3
7	3-Furanylfentanyl	14,375 ± 2638	41.2 ± 7.56	4.09
8	Phenylfentanyl	1498 ± 273	4.29 ± 0.78	N/A
9	Beta′-phenylfentanyl	1660 ± 158	4.76 ± 0.45	N/A

Efficacy estimates are expressed as maximum effect (total distance traveled in cm) and maximum effect as a % of fentanyl’s maximum effect.

Potency estimates are expressed as the dose (mg/kg) required to produce a level of effect equal to 100 m of travel.

The mean maximum effect (distance traveled in cm ± SEM) of all vehicle controls was 1399 ± 62.

Data are mean ± SEM for n = 8–16 mice per dose.

N/A: impossible to estimate based upon the slope of the dose-effect curve.