The pharmacokinetics of alfentanil in children.

The pharmacokinetics of alfentanil were studied in 18 children (3 months to 14 yr of age) undergoing surgery. Alfentanil was administered as a 30-s infusion of either 50 or 120 micrograms.kg-1. Pharmacokinetic values were independent of dose. There was no correlation between Vdss (Volume of distribution at a steady state, measured as l.kg-1) and age or weight, and there was a weak correlation between clearance and age (r = 0.51, P less than 0.05). Vdss and elimination t1/2 were not different in infants less than 1 yr of age when compared to older children. The mean value of Vdss was 0.419 (SE .028) l.kg-1) for the whole group, and elimination t1/2 was 76.3 (SE 6.5) min. The clearance rate [TBC = 7.9 (SE 0.41) ml.kg-1.min-1] was within the range of values previously determined in adult studies. From these data, it would appear that, although there may be differences in the disposition kinetics between children aged 3 months to 14 yr and those measured in adults in some studies by other investigators, age-related differences within this group were not demonstrable.