Objective To determine the impact on glomerular filtration rate (GFR) and tubular function of drugs prescribed to very preterm infants during the first week of life.

Design Prospective multicentre cohort study of infants aged 27–31 weeks gestation.

Methods GFR was measured on day 2, and then weekly for 1 month, with 12-h urine collection by a standardised kinetic Jaffe method. Infants were classified into two groups according to their GFR on day 7 (‘Low GFR’ and ‘High GFR’) with regard to the median reference GFR for their gestational age. Tubular function was also measured weekly for 1 month. Statistical analysis was performed using logistic regression and a repeated measure analysis.

Results Data from 269 infants were analysed, 183 in the ‘Low GFR’ group and 86 in the ‘High GFR’ group. Perinatal factors did not differ in both groups. Significantly more infants were treated with ibuprofen in the ‘Low GFR’ group than in the ‘High GFR’ group, respectively, n=55 (30.0%) versus n=15 (17.4%), whereas aminoglycosides, glycopeptides and all other drugs commonly prescribed during the first week of life did not show a nephrotoxic effect at usual therapeutic dosage.

Conclusions Among all drugs described as nephrotoxic in very preterm infants, ibuprofen alone proved to be nephrotoxic in this study for a 1-month span follow-up. If GFR is lower than the median reference value on day 7 after ibuprofen infusion, physicians should keep in mind that glomerular clearance of drugs may stay decreased for the first month of life.