Background In our hospital, most neonatal inpatients had subtherapeutic serum concentrations of vancomycin in the first therapeutic drug monitoring assessment.

Purpose To evaluate NEOFAX recommendations and to establish a new dosage protocol for vancomycin in neonates to obtain vancomycin serum concentrations of 10–15 µg/mL at the first therapeutic drug monitoring session.

Material and methods A retrospective analysis over a 25 month period from January 2014 to February 2016 was conducted. Hospitalised neonates treated with vancomycin of gestational ages 23–41 weeks were included in the study. The dosage regimen established was based in the manual drug neonatology NEOFAX, which has established the vancomycin dosage as 10 mg/kg, and varying the therapeutic range in relation to gestational age and postnatal age, every 18 hours, 12 hours, 8 hours or 6 hours. To develop a new dosage protocol, we estimated the appropriate dosage for obtaining serum vancomycin trough concentrations between 7.5 and 15 µg/mL using the pharmacokinetics programme PKS.

Results We reviewed the first determination of vancomycin in 43 patients; 60.5% (n=26) were preterm gestational age ≤29 weeks. Of these, 84.6% (n=22) had a postnatal age ≤14 days. 67.4% of all patients had a vancomycin trough concentration before the third dose <7.5 µg/mL, 79% <10 µg/mL, 14% between 10 µg/mL and 15 µg/Ml, and 7% >15 µg/mL.

After the pharmacokinetic study, the pharmacy service and the paediatric department decided to change the dosage protocol and keep track of new patients to evaluate the protocol. For the new protocol we modify the dosing interval established every 18 or 12 hours to every 12 or 8 hours, respectively, and increased the dosage by kg body weight to 12 mg/kg in regimens where the interval was set every 8 or 6 hours. We estimated that 74.4% of serum concentrations of the study patients would have a value between 7.5 and 15 µg/mL.

Conclusion Most of our patients had not attained a correct vancomycin serum concentration at the first determination using the NEOFAX dosage recommendations. Therefore, we have estimated and designed a new dosage protocol to achieve correct vancomycin serum concentrations from the beginning of treatment.

No conflict of interest