Effect of patent ductus arteriosus on gentamicin pharmacokinetics in very low birth weight (less than 1,500 g) babies.

The effect of patent ductus arteriosus (PDA) and its therapy on the pharmacokinetic disposition of gentamicin in very low birth weight neonates was studied. Twenty-four neonates weighing less than 1,500 g with PDA were compared to 16 patients without PDA. Patients with PDA had significantly greater apparent volumes of distribution (0.64 +/- 0.20 vs. 0.41 +/- 0.08 l/kg; p less than 0.001) and serum half-life (8.49 +/- 2.69 vs. 6.23 +/- 1.92 h; p less than 0.01). The total body clearance was not significantly different between the two groups (56 +/- 20 ml/kg/h with PDA vs. 50 +/- 24 ml/kg/h without PDA). In addition, 7 patients were studied before and after PDA closure. The apparent volume of distribution fell in every case (p = 0.02). A statistically significant effect on clearance and half-life was not found. These findings suggest that PDA increases extracellular fluid volume, but does not affect glomerular filtration rate adversely. Additionally, serum gentamicin concentrations must be reevaluated after PDA closure in premature neonates.