Phase I randomized clinical trial of N-acetylcysteine in combination with an adjuvant probenecid for treatment of severe traumatic brain injury in children

Abstract

Background: There are no therapies shown to improve outcome after severe traumatic brain injury (TBI) in humans, a leading cause of morbidity and mortality. We sought to verify brain exposure of the systemically administered antioxidant N-acetylcysteine (NAC) and the synergistic adjuvant probenecid, and identify adverse effects of this drug combination after severe TBI in children.

Methods: IRB-approved, randomized, double-blind, placebo controlled Phase I study in children 2 to 18 years-of-age admitted to a Pediatric Intensive Care Unit after severe TBI (Glasgow Coma Scale [GCS] score ≤8) requiring an externalized ventricular drain for measurement of intracranial pressure (ICP). Patients were recruited from November 2011-August 2013. Fourteen patients (n = 7/group) were randomly assigned after obtaining informed consent to receive probenecid (25 mg/kg load, then 10 mg/kg/dose q6h×11 doses) and NAC (140 mg/kg load, then 70 mg/kg/dose q4h×17 doses), or placebos via naso/orogastric tube. Serum and CSF samples were drawn pre-bolus and 1-96 h after randomization and drug concentrations were measured via UPLC-MS/MS. Glasgow Outcome Scale (GOS) score was assessed at 3 months.

Results: There were no adverse events attributable to drug treatment. One patient in the placebo group was withdrawn due to adverse effects. In the treatment group, NAC concentrations ranged from 16,977.3±2,212.3 to 16,786.1±3,285.3 in serum and from 269.3±113.0 to 467.9±262.7 ng/mL in CSF, at 24 to 72 h post-bolus, respectively; and probenecid concentrations ranged from 75.4.3±10.0 to 52.9±25.8 in serum and 5.4±1.0 to 4.6±2.1 μg/mL in CSF, at 24 to 72 h post-bolus, respectively (mean±SEM). Temperature, mean arterial pressure, ICP, use of ICP-directed therapies, surveillance serum brain injury biomarkers, and GOS at 3 months were not different between groups.

Conclusions: Treatment resulted in detectable concentrations of NAC and probenecid in CSF and was not associated with undesirable effects after TBI in children.

Trial registration: ClinicalTrials.gov NCT01322009.

Fig 1. CONSORT flow diagram.

*in one patient support was withdrawn due to poor neurological prognosis; one patient developed a diffuse rash after administration of study drugs and further administration was discontinued; in one patient the nasogastric tube was removed after extubation and discontinuation of mechanical ventilation, and was not replaced as per study protocol preventing further administration of study drugs.

Fig 2. Serum brain injury biomarkers neuron specific enolase (NSE) and glial fibrillary acidic protein (GFAP) during study period.

Individual NSE corrected for the degree of hemolysis (A) and GFAP (B) values for patients in the placebo (red circles) and probenecid + NAC (Pro-NAC; open blue squares) groups during the study period. There were no differences between groups for NSE (P = 0.441) or GFAP (P = 0.596). Time 0 is in reference to drug administration. Both groups started with seven patients/group. Sample attrition due to patient death, discontinuation of continuous monitoring, or insufficient quantity of serum available to perform the assay.

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.

Fig 4. Mean arterial pressure (MAP), intracranial pressure (ICP), and cerebral perfusion pressure (CPP) during study period.

MAP (A), ICP (B), and CPP (C) in the placebo (red circles) and probenecid + NAC (Pro-NAC; open blue squares) groups during the study period. Time 0 refers to pediatric intensive care unit admission. Median time [range] to first drug dose for the placebo group was 20.5 [14.6–26.0] h and for the Pro-NAC group was 16.5 [8.8–22.0] h. Data are mean and SD; Both groups started with seven patients/group. Sample attrition due to patient death or discontinuation of continuous monitoring.