S(+)‐ibuprofen (S‐IBU) and R(−)‐ibuprofen (R‐IBU) concentrations were measured in 16 neonates with patent ductus arteriosus during a cycle of therapy (three intravenous doses of 10–5–5 mg kg⁻¹ at 24‐h intervals), at the end of the first infusion and 6, 24, 48, and 72 h later. Data were analyzed with a PK model that included enantiomer elimination rate constants and the R‐ to S‐IBU conversion rate constant. The T½ of S‐IBU in the newborn was much longer than in adults (41.8 vs. ≈2 h), whereas the T½ of R‐IBU appeared to be the same (2.3 h). The mean fraction of R‐ to S‐IBU conversion was much the same as in adults (0.41 vs. ≈0.60). S‐IBU concentrations measured 6 h after the first dose were higher than at the end of the infusion in 10 out of 16 cases, and in five cases, they remained higher even after 24 h. This behavior is unprecedented and may be attributable to a rapid R‐to‐S conversion overlapping with a slow S‐IBU elimination rate. In 13 of the 16 neonates, S‐IBU concentrations at 48 and/or 72 h were lower than expected, probably due to the rapid postnatal maturation of the newborn's liver metabolism.

中文翻译：

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动脉导管未闭早产儿的布洛芬对映体：S(+)-布洛芬意外药代动力学特征的初步数据

小号（+） -布洛芬（小号-iBu）和- [R （- ） -异丁苯丙酸（[R -iBu）的浓度在16个新生儿动脉导管未闭治疗的周期（3个静脉内剂量的10-5-5毫克公斤期间测量^-1间隔 24 小时），在第一次输注结束时以及 6、24、48 和 72 小时后。使用包括对映异构体消除速率常数和R - 至S -IBU 转化速率常数的 PK 模型分析数据。新生儿S ‐IBU的T ½比成人长得多（41.8 对 ≈2 小时），而R ‐IBU的T ½似乎相同（2.3 小时）。的平均分数R - 到S -IBU 的转换与成人大致相同（0.41 对 ≈0.60）。16 例中有 10 例在第一次给药后 6 小时测得的S- IBU 浓度高于输注结束时的浓度，在 5 例中，即使在 24 小时后仍保持较高水平。这种行为是史无前例的，可能归因于快速的R到S转换与缓慢的S- IBU 消除率重叠。在 16 名新生儿中，有 13 名在 48 和/或 72 小时时的S- IBU 浓度低于预期，可能是由于新生儿肝脏代谢在出生后迅速成熟。