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Changes in urinary 6β-hydroxycortisol/cortisol ratio after birth in human neonates

  • PHARMACOKINETICS AND DISPOSITION
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Abstract

Objective: Urinary 6β-hydroxycortisol/cortisol (6β-OHF/C) ratio was measured in human neonates to assess the CYP3A enzyme activity.

Methods: Urinary 6β-OHF/C ratio was determined on the day of birth in 94 neonates including those born prematurely. In addition, changes in the ratios after birth were also determined in 81 neonates.

Results: On the day of birth, a significant positive correlation was found between urinary 6β-OHF/C ratios and gestational age (r=0.476) and birth weight (r=0.283). There was no gender difference in the urinary 6β-OHF/C ratios in human neonates. Furthermore, delivery modes such as cesarean section and vaginal delivery did not appear to affect the urinary 6β-OHF/C ratio. The mean ratio of urinary 6β-OHF/C observed in 39 mature neonates (more than 37 weeks of gestational age) was higher than that observed in adults (16.5 vs 9.9). Within 5 days after birth, the ratio rapidly decreased to less than that in adults. In contrast, the mean ratio of urinary 6β-OHF/C observed in 42 premature neonates (under 37 weeks of gestational age) was significantly lower than that observed in mature neonates (5.3 vs 16.5) and was virtually unchanged during the 14-days after birth. Therefore, no significant difference was observed in the mean ratio of urinary 6β-OHF/C between mature and premature neonates at 5 days after birth.

Conclusion: From these results, it was concluded that on the day of birth, mature neonates might possess a higher activity of CYP3A enzyme compared with premature neonates, and that the CYP3A enzyme activity in mature neonates might be promptly changed at an early stage after birth.

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Received: 18 March 1997 / Accepted in revised form: 16 September 1997

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Nakamura, H., Hirai, M., Ohmori, S. et al. Changes in urinary 6β-hydroxycortisol/cortisol ratio after birth in human neonates. E J Clin Pharmacol 53, 343–346 (1998). https://doi.org/10.1007/s002280050390

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  • DOI: https://doi.org/10.1007/s002280050390

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