Background Vancomycin is commonly used in neonatal intensive care for suspected or proven Coagulase Negative Staphylococcus [CoNS] sepsis. Achieving the therapeutic level is important but sub-therapeutic levels are common. There is little data to guide dosage adjustment.

Method A retrospective audit on vancomycin use was undertaken, using standard 24 hourly dose interval in extreme premature babies [< 29weeks]. Finding resulted in a change of dose frequency to 18hrly: a prospective audit was then performed.

Result Of the 27 extreme premature babies on 24 hrly vancomycin, 70% had sub-therapeutic levels; 26% had normal levels. 1 baby [4%] with abnormal renal function had high level.

A subsequent prospective audit of 20 babies [dosed 18 hrly], showed 70% with sub-therapeutic levels, 25% with normal levels; one baby [5%] with abnormal renal function had high level.

The commonest correction for sub-therapeutic levels was to increase the dose by 10%; only 33% of repeat levels were then in normal range. Up to 4 dose increases were required to achieve the therapeutic target.

Conclusion Increasing vancomycin dosing frequency to 18 hrly produced no increase in the number of therapeutic or sub therapeutic levels, but might theoretically result in longer periods of therapeutic drug levels during the course.

On finding the sub-therapeutic levels, there should be flexibility in approach as 10% increase in dose is often ineffective; perhaps, change in frequency should also be considered. More studies are needed to guide the rapid achievement of therapeutic drug levels.