Impact of clinical decision support guidelines on therapeutic drug monitoring of gentamicin in newborns

Our institution's gentamicin dosing and therapeutic drug monitoring (TDM) practices for newborns were suspected to be very heterogeneous. Once-daily dosing (ODD) or extended-interval dosing (EID) and trough concentration measurement were recommended. Clinical decision support guidelines were developed and implemented as clinical decision support in the computerized prescriber order entry system. Impact on dosing, TDM practices, and blood sampling were evaluated.A 1-year retrospective historically controlled study before (April 2008-March 2009) and after the implementation of guidelines (January 2010-December 2010) for newborns (30 days of life) receiving gentamicin. Blood concentrations (% of peak concentrations sampled, % of patients with zero or one concentration sampled, % of trough concentrations ≤1 mg/L) and dose regimen (ODD/EID) were compared between groups. Factors potentially associated with gentamicin concentration were analyzed (multivariate analysis).One hundred thirty-two (postguidelines) versus 102 (preguidelines) patients were included (median gestational age: 34.3 versus 35.8 weeks, P0.05). After implementation of the guidelines, an ODD/EID regimen was almost exclusively used (97.7% versus 61.6%, P0.001), the percentage of peak concentrations (0.9% versus 17.2%, P0.001) and the number of blood samples per patient (87.1% having 0 or 1 concentration measured versus 48.0, P0.001) sharply reduced. A significantly higher percentage of trough concentrations were ≤1 mg/L (68.5% versus 33.0%, P0.001). The probability of a trough concentration ≤1 mg/L increased with an ODD/EID regimen (odds ratio, 7.23; 95% confidence interval: 3.48-15.0, P0.001) and in the postguidelines group (odds ratio, 2.02; 95% confidence interval: 1.01-4.02, P = 0.045).Guideline implementation generated a sharp reduction in blood sampling. Clinical benefits of better gentamicin dosing and TDM practices were evident. Cost-effectiveness and clinical benefit of reduced blood sampling should be evaluated.