Background and Importance The aim of pharmacokinetic monitoring is to improve clinical outcomes. A protocol was agreed between the paediatric and the pharmacy services to establish an initial dosage in this population to reach a therapeutic benefit.

Aim and Objectives To evaluate the initial dosage of these antibiotics by carrying out pharmacokinetic monitoring.

Material and Methods Retrospective observational study from May 2020 to May 2022, including patients treated with vancomycin, gentamicin, or amikacin from the paediatrics service aged <1 year. The following variables were collected at Orion Clinic®: data on age(postnatal, gestational), weight, and dosage. The pharmacokinetic results, creatinine, and pharmaceutical recommendation were collected from Gestlab®.The optimal trough intervals established in the protocol for vancomycin, gentamicin, and amikacin were 10-15 mcg/mL, 0.5-1.5 mcg/mL, 2-5 mcg/mL, and the dosage according to postnatal and gestational age were 10-12mg/kg/8h, 2.5-4mg/kg/24h, 15mg/kg/24-48h, respectively.

Results 231 patients were analysed, 50 treated with vancomycin, 169 with gentamicin and 12 with amikacin. The mean weight was 2.58kg, 2.52kg, and 1.79kg for vancomycin, gentamicin, and amikacin, respectively. Regarding gestational age(GA), in the vancomycin group 22 patients <29weeks, 23 between 30-36, and 5 >37 weeks. For gentamicin, the GA was <29 weeks in 25 patients and >29 weeks in 144. The GA in the amikacin group was <30 weeks in 7 patients,between 30-34 weeks in 4, and >35 weeks in 1 patient. For vancomycin, 58% of patients were treated for suspected sepsis, while gentamicin and amikacin were started empirically in 100% of cases. The initial dosing regimen was in line with the protocol in 86%, 94% and 67% patients for vancomycin, gentamicin and amikacin, respectively. After the first monitoring, 30% patients treated with vancomycin were within the target range, 63% in the case of gentamicin, and 33% for amikacin. A second monitoring was performed, after dosage individualisation, in 35, 19 and6 patients, of vancomycin, gentamicin and amikacin, reaching the objective in 49%, 68% and 67%, respectively.

Conclusion and Relevance In most patients, the initial dosage of the three antibiotics was adjusted to the hospital protocol. A high number of patients treated with vancomycin required dose adjustment, in contrast with gentamicin and amikacin. The role of the pharmacist, together with pharmacokinetic monitoring, is appreciated to achieve optimal concentrations.

Conflict of Interest No conflict of interest