Development and validation of an assay for quantifying budesonide in dried blood spots collected from extremely low gestational age neonates.

•Dried blood spots (DBS) were used to quantify budesonide with a validated UHPLC-MS/MS assay to a sensitivity of 1 ng/mL.•DBS were analyzed for a multi-center clinical study of extremely low gestational age neonates receiving budesonide.•The advantages and disadvantages of DBS as a blood collection method are discussed.•DBS are a valuable low blood volume sampling technique for obtaining serial blood samples in neonates and other children.