Fig 3. Serum and cerebrospinal fluid (CSF) N-acetylcysteine (NAC) and probenecid concentrations during study period.

NAC (A) and probenecid (B) concentrations measured using ultra-high performance liquid chromatography-mass spectrometry (MS)/MS are shown for the placebo (red circles) and probenecid + NAC (Pro-NAC; open blue squares) groups. Data are mean and SEM; sample sizes noted in parentheses (n); LOQ = lower limit of quantification for the assay. Hashed lines represent drug administration times. ¹Sample attrition due to patient death, premature withdrawal from study due to adverse event (rash), inability to continue enteric administration of study drugs after removal of nasogastric tube, and/or removal of or inability to obtain CSF from externalized ventricular drain.