Background and importance Peak (maximum plasma concentration)/MIC >8–15 is a pharmacokinetic (PK)/pharmacodynamic (PD) parameter that best correlates with the effectiveness of aminoglycosides. A peak between 8 and 15 mg/L is necessary to achieve this. In neonates, doses of 3–5 mg/kg/day for the first week and 7.5 mg/kg/day from the second to the fourth week of life are recommended.

Aim and objectives To evaluate the degree of adequacy of the initial dose with current recommendations and whether therapeutic drug monitoring (TDM) allows optimisation of treatment.

Material and methods A retrospective study was conducted from 1 January 2016 to 29 February 2020, in a general university hospital. Patients 0–35 days old treated with gentamicin and with plasma concentrations (Cp) were reviewed. The descriptive analysis was performed with the SPSSV.24 programme.

Results 47 patients with a median age of 3 days (0–33) were studied, 33 male. 26 (55.3%) were <1 week old. 34 (72.3%) were admitted for neonatal sepsis and 7 (14.9%) for urinary infection. Gentamicin was used in combination with ampicillin in 45 cases (95.7%) and empirically in 34 (72.3%). The initially prescribed dose was 4 mg/kg/day in 36 (77%) and 5 mg/kg/day in 8 (17%), with no differences in weeks of life. Cp were extracted with a median of 2 days (1–4) after the start, the median peak was 7.5 mg/L (3.5–21.6) and 29 (62%) had a peak <8 mg/L. The trough was <0.2 mg/L in 26 patients and of those that were quantified, the median was 0.4 mg/L (0.2–1.3), and was higher than 1 mg/L in only one case. It was recommended to increase the dose in 26 (55.3%) and reduce it in 4 (8.5%) patients, with 90% acceptance. A second Cp determination was requested in 16 (34%) cases with a median peak of 9 mg/L (6–12) and trough levels always <0.5 mg/L. It was recommended to increase the dose in 5 cases with an acceptance of 94%.

Conclusion and relevance The dose prescribed was lower than recommended in neonates >1 week old. Cp allowed detection and correction of deviations from the recommended peak or trough levels in 64% of cases, mainly due to low peak levels, with high acceptance of TDM. Plasma determination and TDM of gentamicin continues to be an essential tool to achieve the recommended PK/PD profile.

Conflict of interest No conflict of interest