Background and objective: ibuprofen is rapidly emerging as a new promising drug for treatment of patent ductus arteriosus in preterm infants with possibly less renal side effects as compared to indomethacin. Our aim was to investigate possible changes in pharmacokinetic parameters of ibuprofen in preterm infants with patent ductus arteriosus.

Patients and methods: pharmacokinetics were investigated on day 3 and day 5 in 10 preterm infants (GA: 28.4 ± 1.7 wks, BW: 1120± 410 g, mean ± SD) after a 15-minute i.v. ibuprofen infusion(10-5-5 mg/kg) on 3 consecutive days. Serum concentrations were determined by HPLC-assay.

Results: ibuprofen pharmacokinetics followed a two-compartment open model Peak serum concentrations 1hr after the first and third infusion were 35.6 ± 10.1 and 31.0 ± 10.3 mg/L. Total body clearance (8.7± 5.6 vs 13.8 ± 8.1 mL/hr, p<0.05) and elimination rate constant (0.043 ± 0.028 vs 0.082 ± 0.037, p<0.05) increased significantly, whereas the apparent volume of distribution (0.23 ± 0.14 vs 0.16 ± 0.03 L/kg) and the serum half life (22.1 ± 11.4 vs 11.5 ± 9.2 hr, p<0.05) decreased between day 3 and day 5 after birth during ibuprofen treatment (paired t-test).

Conclusion: these results are a new observation and indicate that the pharmacokinetics of ibuprofen show significant changes between day 3 and day 5 after birth in preterm infants with patent ductus arteriosus, caused by ibuprofen treatment and/or closure of the duct.