Elimination of Ritodrine in Mothers Pregnant with Twins and Their Neonatal Twins

- 94 Abstract This study aimed to clarify the individual elimination kinetics of serum ritodrine in women pregnant with twins and their twin neonates. Serum ritodrine concentrations in 10 twin pregnant women and their twin neonates were measured by liquid chro-matography-tandem mass spectrometry ( LC - MS ／ MS ) using 100 m L of serum. The ritodrine elimination half-life in mothers was 5 . 0 ± 2 . 2 ( 3 . 7 - 11 . 1 ) h ［ mean ± SD ( range )] , while the half-lives of ritodrine in the first and second newborns were 9 . 0 ± 8 . 4 ( 4 . 2 - 29 . 6 ) and 7 . 2 ± 4 . 3 ( 4 . 3 - 13 . 2 ) h, respectively. Large individual differences in the half-life of ritodrine were observed in both mothers and their newborns. Since ritodrine remained in newborn serum for 24 - 48 h after birth, newborns need to be carefully monitored for ritodrine-related complications during