Dose-finding study of ibuprofen in patent ductus arteriosus using the continual reassessment method

Intravenous ibuprofen (IBU) has been found to be as effective as indomethacin for the treatment of patent ductus arteriosus (PDA) in preterm infants and has been associated with fewer adverse effects in comparative phase III studies. The dose regimen used (10-5-5 mg/kg/day) was based on limited pharmacokinetic data and no phase II study was available to determine the optimal dose of IBU for this indication. The present study was designed to determine the minimum effective dose regimen (MEDR) of IBU (one course) required to close ductus arteriosus in preterm infants.

A double-blind dose-finding study was conducted using the continual reassessment method, a Bayesian sequential design. Two distinct target closure rates were initially chosen according to postmenstrual age (PMA) at birth: 80% in infants with a PMA of 27-29 weeks, and 50% in infants with a PMA < 27 weeks. Forty neonates (20 in each PMA group) with PDA were treated between days 3 and 5 of life. Four different dose regimens were tested: loading doses of 5, 10, 15 or 20 mg/kg, followed by two doses (1/2 loading dose) at 24-h intervals. Efficacy was evaluated by echocardiography 24 h after the third infusion.

In infants with a PMA of 27-29 weeks, the estimated MEDR was 10-5-5 mg/kg with a final estimated probability of success of 77% (95% credibility interval: 56-92%). The 15-7.5-7.5 mg/kg dose regimen had a better estimated probability of success (88%, 95% credibility interval: 68-97%), but resulted in more minor renal adverse effects. In contrast, in infants with a PMA < 27 weeks, the estimated MEDR was 20-10-10 mg/kg with an estimated probability of success of 54.8% (95% credibility interval: 22-84%), whereas the conventional dose regimen resulted in a low estimated probability of success (30.6%, 95% credibility interval: 13-56%). In these infants, compared with those with a PMA of 27-29 weeks, minor renal adverse effects were more frequent from the 10-5-5 mg/kg/day dose regimen and did not appear to be clearly dose related.

This study confirms that the currently recommended dose regimen (10-5-5 mg/kg) of IBU is associated with a high closure rate (80%) and few adverse effects in premature infants with a PMA of 27-29 weeks. The failure rate was much higher below 27 weeks. A higher dose regimen (20-10-10 mg/kg) might achieve a higher closure rate. However, tolerability and safety of this dose regimen should be assessed in a larger population before considering the use of these doses for ductus arteriosus closure.