Introduction & Objective: Gentamicin is an aminoglycoside antibiotic widely used during the neonatal period. It is associated with nephrotoxic effects in neonates, including glomerular impairment and renal tubular dysfunction. Electrolyte balance is very important, especially in the sick premature neonate receiving aminoglycosides. The purpose of this study was early diagnosis of gentamicin nephrotoxicity.

Materials & Methods: This quasi-experimental study was performed on 23 neonates (11 full – term and 12 preterm) with suspected sepsis who were admitted and treated with gentamicin. Blood and urine samples were collected before infusion and on the 3rd day of treatment. Serum and urine concentration of Na, K, creatinine (Cr) and urine concentration of Ca were measured. Then fractional excretion of Na and K were estimated. Ca excretion was estimated as the UCa/UCr ratio. Then the collected data were analyzed using SPSS package.

Results: In all neonates, increase in fractional excretion of Na and UCa/UCr, in the 3rd day of treatment were observed as compared to those of before infusion (P=0.01 and P=0.02 respectively). Serum creatinine levels decreased in all patients. Serum level of electrolytes during therapy was normal.

Conclusion: The results of this study clearly demonstrate an effect of gentamicin infusion on renal sodium and calcium excretion. These results may be of clinical importance especially for sick preterm neonates receiving treatment with gentamicin. These babies are usually salt-losers and are also more susceptible to early onset hypocalcemia. Gentamicin can aggravate these complications.