During pregnancy, the clearance of pancuronium and vecuronium is increased, resulting in a shorter elimination half-life. The aim of this study was to determine the influence of pregnancy on the disposition in the body of atracurium. Eight ASA (American Society of Anesthesiologists) I pregnant women and 8 ASA I nonpregnant women were included in this study. A dose of 0.3 mgsol;kg was administered to both groups with the exception of 3 pregnant women who received 0.2 mgsol;kg. For pregnant women, atracurium was administered after clamping of the umbilical cord. Venous blood samples were collected at the following times: 0, 1, 2, 3, 5, 7, 10, 15, 20, 30, 45, 60, 80 and 100 minutes. Plasma concentrations of atracurium were measured using a specific HPLC assay. Pharmacokinetic results were similar for both groups: rapid distribution half-life 2.25 plusmn; 0.86vs2.22 plusmn; 0.91 minutes; elimination half-life: 16.3 plusmn; 2.9vs17.8 plusmn; 3.6 minutes; mean residence time 18.2 plusmn; 3.8vs17.6 plusmn; 2.7 minutes; clearance 6.91 plusmn; 1.70vs6.56 plusmn; 1.27 mlsol;minsol;kg; and apparent volume of distribution at steady-state 0.126 plusmn; 0.034vs0.116 plusmn; 0.021 Lsol;kg for pregnant women and nonpregnant women, respectively.We conclude that the disposition of atracurium is not modified by the physiological changes of pregnancy. This is most probably because of the unique mode of elimination of atracurium, i.e. Hofmann elimination and nonspecific ester hydrolysis.
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