Plasma (Black Line) and Effect-Site (Red Line) Concentrations Following a Bolus Dose of Fentanyl (A) or Alfentanil (B)

(Reused from Scott JC, Stanski DR. Decreased fentanyl and alfentanil dose requirements with age. A simultaneous pharmacokinetic and pharmacodynamic evaluation. J Pharmacol Exp Ther. 1987;240:159-166.)

Plasma (black line) and effect-site (red line) concentrations following a bolus dose of fentanyl (A) or alfentanil (B).