Difference in Ritodrine Pharmacokinetics between Singleton and Twin Pregnancies

抄録

Aim: To determine the pharmacokinetics of ritodrine in singleton and twin pregnancies.
Methods: We treated 105 pregnant women (with singletons, n=67; with twins, n=38) with continuous infusion of ritodrine and then measured steady-state serum ritodrine concentrations using HPLC.
Results: Ritodrine clearance (mean ± SD) was significantly lower in women who delivered twins than in those who delivered singletons (1.59 ± 0.30 vs. 1.75 ± 0.43 L/h/kg; p<0.001). Serum ritodrine concentration did not differ significantly between women who delivered preterm singletons and those who delivered preterm twins (97.5 ± 61.1 vs. 89.6 ± 50.4 ng/mL; p=NS), but was significantly higher in women who delivered twins at term than in those who delivered singletons at term (85.8 ± 39.7 vs. 65.7 ± 38.7 ng/mL; p<0.001).
Conclusion: Ritodrine clearance was lower in twin pregnancies than in singleton pregnancies. The dose of ritodrine administered to maintain pregnancy should be controlled taking into account singleton or twin pregnancy.
(Jpn J Clin Pharmacol Ther 2013; 44(5): 389-394)