Ibuprofen, the active ingredient in Nurofen and Advil, is a commonly used drug in children. There is very limited data about Ibuprofen concentrations in the cerebro spinal fluid (CSF). The objective of the current study is to describe concentrations of ibuprofen in the CSF of infants and children after administration of ibuprofen. We will study infants presenting to the Emergency Department (ED) with fever who received ibuprofen. A complete sepsis workup including sampling of blood and CSF is conducted in cases of suspected meningitis. We will measure ibuprofen in the blood and CSF obtained during the sepsis workup. A better understanding of the pharmacokinetics of ibuprofen and its penetration into the CSF will unable us to suggest more accurate dosing guidelines, and to better predict the effects of this commonly used drug.