BACKGROUND: Advances in neonatology have contributed to changes in the drug utilisation profile in neonates, both in the number of drugs and the pharmacotherapeutic groups. OBJECTIVE: To analyse drug use in the neonatal care unit of a teaching hospital in Brazil and to evaluate the associations among perinatal, clinical care and drug use data. SETTING: The neonatal care unit of a teaching hospital in Brazil. METHODS: A prospective observational study was conducted. Perinatal, clinical care and pharmacotherapy data were collected from the patients' medical records. Labelling information regarding neonatal use was analysed for prescribed drugs. The data were analysed using univariate descriptive statistics and quasi-Poisson regression. MAIN OUTCOME MEASURE: Frequency of drug use by gestational age. RESULTS: The study included 187 patients; 157 (84.0 %) received drugs. The mean gestational age was 35.8 weeks. The mean number of drugs prescribed per patient was 6.4. The number of drugs used was inversely correlated to gestational age and birth weight. The most commonly prescribed drugs belonged to the following anatomical therapeutic chemical groups: nervous system drugs, anti-infectives for systemic use, and alimentary tract and metabolism drugs. Information regarding neonatal use was given in the labelling of only 20.5 % of the prescribed drugs. Of these, only 9.5 % had information specific for preterm infants. CONCLUSIONS: Drug administration to neonates is frequently and inversely correlated to gestational age and birth weight. Neonates are exposed to different therapeutic classes, reflecting scientific advances in neonatology. In Brazil, the percentage of drugs with neonate-specific labelling information is low. Consequently, there is an evident need for efforts to guarantee effective and safe pharmacotherapy for neonates.