We studied the pharmacokinetics after caudal block of ropivacaine (2 mg ml(
-1), 1 ml kg(-1)) performed in 20 children aged 1-8 yr undergoing subumbili
cal surgery, in this open, noncomparative, multicentre study. Venous blood
samples were collected up to 12-36 h. The mean (SD) peak plasma concentrati
on, 0.47 (0.16) mg litre(-1), was achieved after 12-249 min. The free fract
ion was 5% and the highest individual peak plasma concentration of free rop
ivacaine was 0.04 mg litre(-1). Clearance was 7.4 (1.9) ml min(-1) kg(-1) a
nd the terminal half-life 3.2 (0.8) h. Thus, the free plasma concentrations
of ropivacaine were well below those associated with toxic symptoms in adu
lts and the capacity to eliminate ropivacaine seems to be well developed in
this age group. In this open study of 20 patients, ropivacaine was well to
lerated and provided satisfactory postoperative pain relief without observa
ble motor block.