Serum calcium values in term and late-preterm neonates receiving gentamicin

Since noting an apparent increase in hypocalcemia in neonates receiving gentamicin every 24 h (q 24 h) for >4 days, we have prospectively monitored serum calcium (Ca) values in these patients receiving prolonged gentamicin therapy. This study is a retrospective analysis of those values measured during gentamicin treatment. The study included neonates with gestational age >35 weeks who received >4 days of gentamicin therapy and in whom at least one serum Ca value was measured >47 h after initiation of therapy. Hypocalcemia was defined as a serum Ca level <8 mg/dl (2 mmol/l). Data were analyzed by Student t-test, chi-square test, and Pearson product moment correlation. There were 1,624 neonates that met the study criteria. Ca was <8 mg/dl in 241 (15%). Ca <8 mg/dl was more likely in boys than in girls (16.4% vs 11.8%, P=0.01) and in neonates <37 weeks gestational age (GA) than in those ≤37 weeks GA (23.9% vs 14.1%, P=0.01). A second Ca value was obtained in 883 neonates (54%); 23.2% of neonates with initial Ca <8 mg/dl remained hypocalcemic, and 30% of these were receiving oral Ca supplementation. The second Ca value was <8 mg/dl in eight neonates in whom initial Ca was >8 mg/dl. Hypocalcemia is not uncommon in neonates receiving gentamicin therapy, and it may occur more frequently in boys and late-preterm infants. These data suggest that the monitoring of serum Ca levels should be considered when gentamicin is given >4 days.