Pharmacokinetics of transdermal fentanyl in the peri-operative period in young children

The pharmacokinetics of transdermal fentanyl were assessed in eight childre n aged 18-60 months, weighing 11-20 kg and monitored postoperatively in the intensive care unit. A patch, delivering 25 mug.h(-1) of fentanyl, was app lied for 72 h from the induction of anaesthesia. Plasma fentanyl concentrat ions were measured over 144 h. Mean (SD) peak concentration of fentanyl was 1.7 (0.66) ng.ml(-1) and time to reach maximal plasma concentration was 18 (11) h. The elimination half-life was 14.5 (6.2) h, and the area under the curve for plasma fentanyl concentration (0-144 h) was 86.8 (27) ng.h.ml(-1 ). Maximal fentanyl concentration was negatively correlated with patient ag e (r = -0.71; p = 0.049) but not with body weight. These results suggest th at the pharmacokinetics of transdermal fentanyl in children are similar to those in adults.