Background and importance Absence of a standardised method to measure antimicrobial consumption in the neonatal population

Aim and objectives Establish a conversion factor that makes possible to relate the defined daily dose (DDD) of the adult population and the DDD of the neonatal population.

Materials and methods National, multicentre and retrospective study. It had the participation of 10 third-second level hospitals and a multidisciplinary team: hospital pharmacists, paediatricians, neonatologists and infectious disease experts.

First, after selecting the antimicrobials for study based on the literature and routine clinical practice, the Delphi methodology was used to agree on the recommended dose for its most common indication in the neonatal population. Two rounds of consultation with the group of experts were carried out. For those antimicrobials whose dose was not agreed upon, the dose established in Pediamecum was selected.

The weight and gestational age of the neonates (<1 month) admitted to 6 hospitals during 2018 were collected through the admission records or own records of the pharmacy or neonatology services of these hospitals. The mean, median, standard deviation and maximum and minimum of each of the variables were calculated.

Subsequently, the DDD in grams of each antimicrobial were calculated.

Finally, the conversion factor was obtained by comparing the DDD designed for neonates (DDDn) with the DDD validated by the WHO for adults (DDDa).

For the analysis of the results, the statistical package IBM SPSS Statistics version 19 was used.

Results 4820 neonates were selected. The mean weight was 2687 g(6080–440).

The conversion factor (DDDn/DDDa) of the parenterally administered antimicrobials were: amikacin (0.04), amoxicillin (0.03), amoxicillin-clavulanate (0.09), ampicillin (0.04), liposomal amphotericin B (0.38), azithromycin (0.05), aztreonam (0.06), cefazolin (0.04), cefepime (0.07), cefotaxime (0.07), ceftazidime (0.07), ceftriaxone (0.07), ciprofloxacin(0.05), erythromycin(0.13), fluconazole(0.08), gentamicin (0.04), imipenem-cilastatin (0.07), linezolid (0.07), meropenem (0.04), metronidazole (0.03), micafungin (0.05), penicillin G sodium (0.03), piperacillin-tazobactam (0.04), teicoplanin (0.04), and vancomycin (0.04)

Those obtained from oral antimicrobials were: amoxicillin (0.05), amoxicillin-clavulanate (0.08), azithromycin (0.09), cefadrozil (0.04), cefixime (0.05), ciprofloxacin (0.05), clindamycin (0.03), cloxacillin (0.07), erythromycin (0.13), fluconazole (0.08), Fosfomycin (0.09), itraconazole (0.04), linezolid (0.07), metronidazole (0.04) and vancomycin (0.05).

Conclusion and relevance Analysing the demographic characteristics of the neonatal population, the DDD of the antimicrobial group can be standardised, this allows establishing a conversion factor with respect to the adult DDD. A new study to confirm the validity of designed neonatal DDD and hence the conversion factor between neonatal DDD and adult DDD is underway.