A,F,S, or M indicates which opioids are significantly different from that opioid for that parameter.
* Indicates P < 0.05 compaired with other opioids. A = alfentanil; AUC = area under concentration–time curve; Conc. = concentration; F = fentanyl; M = morphine; MRT = mean residence time; S = sufentanil; Terminal elim. t1/2= terminal elimination half life; UM = unmeasureable; Vd = volume of distribution.