Concurrent frusemide-theophylline dosing reduces serum vancomycin concentrations in preterm infants

Abstract

Objective: To document serum vancomycin concentrations in preterm infants on concurrent fursemide-theophylline therapy and to observe the effect of this drug combination on serum creatinine concentrations. Method: Ten preterm infants in our Neonatal Intensive Care Unit on regular theophylline treatment for apnoea of prematurity who subsequently received vancomycin and frusemide were studied. Patient age, drug dosages, serum vancomycin and serum creatinine concentrations were recorded. Results: When vancomycin was introduced in those cases established on both frusemide and theophylline, there was a consistent failure to achieve anticipated therapeutic concentrations. Starting frusemide treatment in those infants already receiving vancomycin resulted in falls in serum vancomycin to subtherapeutic concentrations in all but one case. Serum creatinine concentrations in all infants fell by a mean of 24.4% (11.7-43.3%) in the 24 hours following the initiation of frusemide treatment. Two of the ten infants had persistence of coagulase negative staphylococcal sepsis while their vancomycin concentrations were subtherapeutic. Conclusion: Preterm infants receiving both theophylline and frusemide may need a shorter vancomycin dose interval to avoid therapeutic failure.