In neonatology unit 40 to 80% of the drugs are used as off-label or unlicensed, particularly in Neonatal Intensive Care Unit (NICU), where it has been described that in a single patient up to 60 parenteral drugs can be administered. The course of a drug inside the organism can be defined in 4 different phases: absorption, distribution, metabolism, elimination; for each of these phases the newborn infant has different characteristics than child and adult. In the last years much more attention has been put in pharmacological research specific for the neonatal age and a good trial design should take into account the following points: (1) to define the pediatric disease in terms of natural history, prevalence, severity, treatment and impact of the new drug; (2) to avoid the "try and error" method based on the adult dose corrected for weight or age; (3) to use adapted methodologies (pharmacokinetics); (4) to avoid small clinical trials (limited number of patients), the use of Randomized Controlled Trials rather than observational studies; (5) to consider ethics providing clear information and reducing pain and stress to the baby and its family.