gms | German Medical Science

Background: Providing optimal pain therapy is a major concern in neonatal intensive care units (NICUs). Metamizole is an established therapeutic option in Germany. However, its use is controversial worldwide due to rare but serious risks of serious adverse effects such as agranulocytosis. Furthermore, intravenous metamizole is only approved for use in children aged 3 months and older. In Germany, there is little data on metamizole use at NICUs. Therefore, we aimed to study the use and dosage of metamizole in neonates and infants under 2 years of age in our NICU.

Materials and Methods: A retrospective database analysis was performed using routine medication data from patients under the age of 2 years treated in our local NICU between 2013 and 2022. We characterized 7010 inpatient stays of 6555 different patients with medication and analysed the metamizole use. The population was divided into three age groups, neonates <28 days (6076 inpatient stays), infants ≥28 days – <3 months (416 inpatient stays) and infants ≥3 months – <2 years (518 inpatient stays) and the frequency of metamizole exposure determined. Based on the dosing information available from routine data we calculated the mean weight-based daily metamizole dose stratified by age group. Additionally, we calculated the number of neonates receiving multiple doses of metamizole.

Results: Overall, metamizole exposure rate was 14.6% (1025/7010 inpatient stays). Of 6076 neonatal admissions, 10.3% (624) received metamizole. The corresponding exposure rates were 42.3% (176/416) for infants between 28 days and 3 months and 43.4% (225/518) for infants between 3 months and 2 years. The mean single dose of metamizole was similar across age groups with 11.1 mg/kg for neonates and 11.3 mg/kg and 11.9 mg/kg for infants between 28 days and 3 months and infants between 3 months and 2 years, respectively. Multiple doses of metamizole were administered in almost 59% of cases less than 28 days old.

Conclusion: Metamizole is frequently used in the NICU including in neonates. A multicentre study is needed to validate these finding and exclude local effects. Furthermore, because there are few evidence-based (dosing) recommendations for neonates and infants, further pharmacokinetic and safety data are needed to ensure safe and effective therapy when using this drug in this vulnerable population.