Figure 11-17 Time to reach brain concentration after simultaneous bolus applications of fentanyl, sufentanil, and alfentanil. The fraction of peak brain concentration results from the amount of drug extracted from arterial blood (arterial-jugular bulb concentration difference, integrated over time) plotted as a fraction of the cumulative absorption. Data are presented as the median (solid lines) and 50th and 95th percentiles (dotted lines) from individual patients. (From Metz C, Gobel L, Gruber M, et al: Pharmacokinetics of human cerebral opioid extraction: A comparative study on sufentanil, fentanyl, and alfentanil in a patient after severe head injury. Anesthesiology 92:1559–1567, 2000.)