Background and objectives:

Antimicrobial consumption is frequently measured using the daily defined dose (DDD) system assigned by WHO to every antimicrobial drug. DDD is the presumptive average maintenance daily dose of a drug used for its main indication in adults. The fact that the existing DDDs are derived from adult doses could compromise the validity of this tool in studies involving paediatric patients. Since drug doses in children are most frequently based on body weight (BW), the calculation of paediatric DDDs should take into account the mean BW of children admitted to a paediatric unit. Our objective was to develop a method for the calculation of paediatric and neonatal DDDs, for common antimicrobial drugs used in a tertiary hospital.

Methods:

We calculated the mean BW of 229 children consecutively admitted to the paediatric wards of our hospital. We then calculated the paediatric DDD for a given antimicrobial with the equation: ped DDD = mean BW (kg) × dose (mg/kg), where dose (mg/kg) is the average or usual recommended paediatric dose of the drug, according to approved textbooks or formularies. For neonatal DDDs, we multiplied the mean BW of 255 infants consecutively admitted to the neonatal unit [(birth weight + discharge weight) / 2] with the average or usual recommended neonatal dose of the drug. We used ceftriaxone to apply our proposed paediatric and neonatal DDD system.

Results:

The mean BW of the paediatric patients was 18.42 kg (95% CI: 16.48–20.35 kg) and that of the hospitalised neonates was 2.57 kg (95% CI: 2.48–2.66 kg). Based on our method, with an average paediatric dose of 75 mg/kg and a neonatal dose of 50 mg/kg of ceftriaxone, the paediatric DDD was found to be 1.4 g and the neonatal DDD 0.13 g. By employing the DDD assigned to ceftriaxone by WHO (2 g), the consumption of this drug during 2002 in three different departments of our hospital (adult, paediatric, neonatal) was 5.11, 2.87 and 1.09 DDDs per 100 bed-days, respectively. By using, however, the adjusted DDD system for the paediatric and neonatal wards, the consumption was found to be 5.11, 4.11 and 16.83 DDDs per 100 bed-days, respectively.

Conclusion:

The development of paediatric and neonatal DDDs with this BW-based approach, using collective data from different hospital departments and countries, could greatly facilitate antibiotic consumption studies involving paediatric or neonatal units.