Table 2.
Results from warm-water tail-withdrawal tests.
| # | Drug | %Emax ± SEM | Agonist ED50 mg/kg (95% CI) | Agonist + Antagonist ED50 mg/kg (95% CI) | Fold change (agonist + antagonist / agonist) | Potency ratio to morphine | Potency ratio to fentanyl |
|---|---|---|---|---|---|---|---|
| 1 | Morphine | 94.0 ± 5.98 | 7.82 (5.42–11.0) | 11.6 (5.98–23.8) | 1.48 | 1.00 | 0.01 |
| 2 | Fentanyl | 89.2 ± 10.8 | 0.08 (0.04–0.16) | 0.32 (0.15–0.62) | 3.95 | 97.7 | 1.00 |
| 3 | Beta-methylfentanyl | 100 | 0.74 (0.64)-0.85) | 14.2 (8.27–31.0) | 19.2 | 10.6 | 0.11 |
| 4 | Para-methylfentanyl | 100 | 1.92 (1.48–2.45) | 121 (62.7–345) | 63.1 | 4.07 | 0.04 |
| 5 | Para-methoxyfentanyl | 100 | 0.43 (0.23–0.77) | 9.62 (3.81–38.2) | 22.5 | 18.3 | 0.19 |
| 6 | Fentanyl carbamate | 91.6 ± 3.06 | 5.59 (4.11–7.54) | 12.4 (7.72–20.9) | 2.21 | 1.40 | 0.01 |
| 7 | 3-Furanylfentanyl | 100 | 0.51 (0.36–0.74) | 10.6 (5.29–21.0) | 20.6 | 15.3 | 0.16 |
| 8 | Phenylfentanyl | 48.0 ± 9.24 | 55.2 (33.5–93.0) | 289 (187–515) | 5.23 | 0.14 | 0.0015 |
| 9 | Beta′-phenylfentanyl | 55.9 ± 5.14 | 19.4 (11.0–34.4) | 407 (187–2294) | 21.0 | 0.40 | 0.0041 |
Efficacy estimates are expressed as %Emax (maximum %MPE).
Potency estimates are expressed as ED50 (mg/kg) values for drug alone, ED50 values for drug following a 1 mg/kg, SC naltrexone pretreatment, fold change between (agonist + antagonist)/(agonist) potency, drug potency ratio to morphine, and drug potency ratio to fentanyl.
Data are mean ± SEM or 95% confidence intervals for n = 8 mice per dose.