ED50 values of different mu opioid agonists for decreasing minute volume in the presence of 5% CO2 during the baseline and the single-dose phases2-a
| Drug | Base Line | Single Dosing |
|---|---|---|
| Fentanyl | 0.020 ± 0.012 | 0.011 ± 0.001 |
| Nalbuphine | 0.961 ± 0.215 | 0.847 ± 0.313 |
| Butorphanol | 0.056 ± 0.018 | 0.035 ± 0.010 |
| Ethylketazocine | 0.015 ± 0.001 | 0.014 ± 0.003 |
↵2-a Values given are group means ± S.E. in milligrams per kilogram and were determined from linear regression of individual dose-response curves.