Pharmacokinetics of oral ibuprofen in premature infants

Patent ductus arteriosus (PDA) is a frequent complication in premature infants. So far, intravenous indomethacin is the standard mode of medical therapy in such patients but carries a risk of frequently occurring side effects. Ibuprofen, another nonsteroidal anti-inflammatory drug, has also been shown to be efficacious in closing ductus with lesser adverse effects after parenteral administration. However, limited data are available on the pharmacokinetics of intravenous ibuprofen in this population. Nonavailability of parenteral preparation and lack of information regarding pharmacokinetic disposition of ibuprofen in this subgroup of the population led the authors to conduct this pharmacokinetic study with oral ibuprofen. Twenty premature infants with a gestational age of 30.45 +/- 0.33 weeks and a birth weight of 1262.5 +/- 55.4 g (values given as mean +/- SEM) admitted to the neonatal unit were enrolled in this study. Ibuprofen was administered in a single oral dose of 10 mg/kg between 4 and 72 hours postnatally, and blood samples were collected through an indwelling vascular catheter at time 0 and 1, 2, 4, 8, 12, and 24 hours. Ibuprofen plasma concentrations were assayed by high-performance liquid chromatography. There was a large interindividual variability observed for plasma concentrations, elimination half-life (t1/2) (15.72 +/- 3.76 h), and area under the plasma concentration-time curve (AUC0-infinity) (402.60 +/- 79.67 micrograms.h/mL) in these babies. Variables such as gestational age, birth weight, and sex did not affect ibuprofen pharmacokinetics significantly (p > 0.05). Moreover, no correlation could be found between elimination half-life and gestational age (r = 0.02). Ibuprofen pharmacokinetics showed a wide variability in premature infants. The results of the present study warrant revising the oral dosage schedule to achieve comparable plasma concentrations of ibuprofen associated with successful closure of ductus, as reported in earlier studies.