Gentamicin serum concentration measurement in children

Gentamicin is often used to treat serious paediatric infections. It has been standard practice in Norway to measure the serum concentration of gentamicin immediately prior to the second or third dose (pre-dose [trough] concentration) to assess the risk of toxicity. The clinical significance of such measurements in children has not previously been evaluated in Norway.

This is a retrospective study of routine pre-dose samples obtained for the measurement of serum gentamicin in paediatric patients aged 1 month to 17 years at four hospitals in Norway. Clinical data were extracted from electronic medical records from two of the hospitals. All children received treatment with intravenous gentamicin at a dose of 7 mg/kg once daily in accordance with Norwegian guidelines.

The most common indications for treatment were febrile urinary tract infection, febrile neutropenia, and suspected or confirmed sepsis. The median (interquartile range) duration of treatment in 353 episodes at two of the hospitals was 4 (3-5) days. Serum gentamicin pre-dose samples were analysed for 1,288 treatment episodes across four hospitals. In 1,223 episodes (95 %), the pre-dose sample showed a serum gentamicin concentration of less than 0.6 mg/L. In 7 episodes (0.5 %), the pre-dose sample showed an elevated gentamicin concentration, defined as greater than 1.0 mg/L.

An in most cases mildly elevated serum gentamicin concentration was found in the pre-dose sample in 7 of 1,288 treatment episodes. Routine measurement of serum gentamicin via a pre-dose sample should in future be reserved for children receiving long-term gentamicin treatment, those with impaired kidney function, or those who are also receiving nephro- or ototoxic drugs.