P124
ONCE DAILY GENTAMICIN DOSES IN NEWBORN INFANTS
Singh GR, Sheffield S, Whitehall JS
NICU, Kirwan Hospital for Women Thuringowa, Qld 4817
Gentamicin is the most commonly used aminoglycoside and is selected as initial antibiotic therapy in most
NICUs all over the world. Traditionally, Gentamicin has been given in 2-3 divided doses but in recent years
there has been increasing evidence that a single daily dose regime leads to less toxicity while retaining equal
efficacy.
The aim of this study was to compare the peak and trough levels while using the traditional multiple dose
regime versus a single daily dose regime which uses a loading dose for preterm babies of less than 34 weeks
gestation..
A cohort of babies admitted to the NICU at Kirwan from January to October 1997 were studied.
A change in the gentamicin policy was instituted in April 1997. The new policy incorporated a
loading dose of 5mg/kg followed by 3.5mg/kg every 24 hours (30-34 weeks) or every 36 hours
(<30 weeks) and a single daily dose of 4mg/kg for those above 34 weeks. Trough and peak
gentamicin levels were obtained for all babies pre and post the third dose.
On the traditional regime 76.3% of all babies had trough levels of > 2mg/dl, of which 48.5% had very high
levels; while on the new regime 13.6% (18/57) had toxic trough levels; and only 14% had very high values. The
difference between trough levels between the old and the new regime was statistically significant (p<0.0001).
On the old regime 81.6% (31/38) had achieved adequate peak levels. On the new regime peak concentrations
were achieved in 94.5 % (52/55). This difference was also statistically significant (p<0.05). Factors which could
influence renal function such as creatinine levels and the concomitant use of other drugs were also studied
although numbers were too small for statistical analysis.
The attainment of early therapeutic peak gentamicin levels is associated with better outcomes in patients with
severe sepsis. A loading dose given to preterm babies allows them to achieve adequate therapeutic levels despite
their large volumes of distribution. The longer dosage intervals allow time for clearance of the drug by their
relatively immature kidneys.
In conclusion, changing to the new Gentamicin regime reduced the percentage of high trough levels
significantly, clearly minimising the risk of toxicity, while allowing adequate peak values to be achieved quickly
in most babies.