PHARMACOEPIDEMIOLOGY AND PRESCRIPTION Off-label use of antimicrobials in neonates in a tertiary children’s hospital Niina Laine 1,2 & Ann Marie Kaukonen 3,4 & Kalle Hoppu 1,5 & Marja Airaksinen 2 & Harri Saxen 1 Received: 20 August 2016 /Accepted: 9 January 2017 # Springer-Verlag Berlin Heidelberg 2017 Abstract Purpose Off-label (OL) use of drugs for hospitalized children is very common. OL use occurs especially in the youngest patients, neonates. This study focused on the OL use of anti- microbials in neonates. To our knowledge, only few studies have focused on the prevalence of OL use of antimicrobials in neonates. Methods We investigated the OL use of antimicrobials in ne- onates in a tertiary children’s hospital. First, we investigated what were the most consumed OL antimicrobials in defined daily doses according to hospital’s registry data from neonatal intensive care unit (NICU) during 2009–2014. Second, we conducted a targeted retrospective study of premature neo- nates (400–2000 g) with blood culture-positive infections and receiving antimicrobial therapy between 2005 and 2014 (N = 282). The data were obtained from the electronic patient records and from the hospital’s electronic infection registry. Statistical analysis was conducted by using a univariate logis- tic regression model fitted for OL usage. Results In NICU, 35% (7/20) of antimicrobials used were OL. Eighteen percent (51/282) of premature neonates with blood culture-positive infections received at least one antimicrobial OL. The most commonly used OL antimicrobials in neonates were meropenem 88% (45/51), rifampicin 18% (9/51), and ciprofloxacin 8% (4/51). The odds for OL use were signifi- cantly higher the smaller the neonate birth weight was. An increase in birth weight was found to statistically significantly decrease the probability of OL usage (odds ratio = 0.85 for 100 g increase in birth weight, p value <0.001). Conclusion More studies in neonates on especially dosing and pharmacokinetics of antimicrobials are urgently needed. Keywords Off-label use . Paediatric . Children . Antimicrobial . Premature neonate . Neonatal intensive care unit (NICU) Introduction For market authorization labelling, data on the safety and ef- ficacy of pharmaceuticals must be submitted to the regulatory authorities by the pharmaceutical companies. Based on the data submitted, a drug can be authorized by the regulatory authorities, and the approved labelling, with information on indication and dosing and in the age groups the drug has been The views expressed in this article are the personal views of the author(s) and may not be understood or quoted as being made on behalf of or reflecting the position of the European Medicines Agency or one of its committees or working parties. Electronic supplementary material The online version of this article (doi:10.1007/s00228-017-2200-z) contains supplementary material, which is available to authorized users. * Niina Laine niina.laine@helsinki.fi Harri Saxen harri.saxen@hus.fi 1 Children’s Hospital, Helsinki University Hospital, Stenbäckinkatu 11, 00029 HUS Helsinki, PL 281, Finland 2 Department of Pharmacology and Pharmacotherapy, Faculty of Pharmacy, University of Helsinki, Viikinkaari 9, 00014 Helsinki, Finland 3 Formulation and Industrial Pharmacy Unit, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland 4 Current address: Finnish Medicines Agency (FIMEA), P.O. Box 55, 00034 Helsinki, Finland 5 Poison Information Centre, Helsinki University Hospital, Helsinki, Finland Eur J Clin Pharmacol DOI 10.1007/s00228-017-2200-z