Overcoming Membrane Transporters to Improve CNS Drug Delivery - Improving Brain Antioxidants After Traumatic Brain Injury (Pro-NAC)

The overall purpose of this research study is to investigate the safety of pharmacological therapies that may potentially improve pediatric outcomes after traumatic brain injury. Traumatic brain injuries are the leading cause of death and disability among children and young adults.

Hypothesis: Combinational therapy with a membrane transporter and antioxidant are safe after TBI and can overcome barriers to the brain and synergistically improve bioavailability and efficacy the antioxidant content of the body and CNS after TBI.

Specific Aim: Define the capacity of the combination of probenecid and NAC to safely and synergistically preserve levels of GSH and reduce oxidative stress in children with severe TBI. We will enroll 20 children age 2 to less than 18 years old (less than 216 months) after severe TBI in a randomized, controlled study of administration of the combinational therapy and test if the administration of these drugs is safe and if antioxidant reserve can be preserved within the serum and CSF.

Probenecid (at the same dose that is used as an adjunct to antibiotic therapy) and NAC (at the same dose that is used for acetaminophen-induced liver disease), or vehicles will be given for 3 days. The primary outcomes of the study will be the safety of drug administration and the CSF and serum levels anti-oxidant reserve (AOR), with the presumption that maintaining anti-oxidant levels within the brain may prove neuroprotective. Other secondary outcomes (CSF and serum probenecid, NAC, GSH and phenytoin concentrations) will also be tested. Adverse events occuring during treatment with these drugs after TBI will be monitored by a local Data Safety Monitoring Board.

• Drug: Probenecid and N-acetyl cysteine
  After obtaining written parental consent, patients will be randomized by the use of a blind envelope system to one of the following: to receive probenecid (initial: 25 mg/kg/dose; maintenance: 10mg/kg/dose 4 x per day for 11 doses) and NAC (initial: 140mg/kg/dose; maintenance: 70mg/kg/dose 6 x per day for 17 doses) or the placebo via nasogastric (NG) or orogastric (OG) tube for 3 days or to receive placebos.
• Drug: Placebo
  After obtaining written parental consent, patients will be randomized by the use of a blind envelope system to one of the following: to receive probenecid (initial: 25 mg/kg/dose; maintenance: 10mg/kg/dose 4 x per day for 11 doses) and NAC (initial: 140mg/kg/dose; maintenance: 70mg/kg/dose 6 x per day for 17 doses) or the placebo via nasogastric (NG) or orogastric (OG) tube for 3 days. Placebo contents include equal volumes and dosing regimens of lactose powder (for opacity) suspended in Ora-Plus and normal saline.
  Other Name: Ora Plus

• Experimental: Drug
  Probenecid and N-acetyl cysteine will be administered at standard doses for the first 4 days after TBI.
  Intervention: Drug: Probenecid and N-acetyl cysteine
• Placebo Comparator: Placebo
  Placebos will be prepared for the two experimental drugs and administered at identical time periods.
  Intervention: Drug: Placebo

Inclusion Criteria:

• Children (age 2 - 18 y) with severe TBI (GCS < or = 8) with an externalized ventricular drain placed for measurement of intracranial pressure

Exclusion Criteria:

1. Brain dead on admission to ICU
2. Pregnancy
3. Contraindications to enteral medications

4. Contraindications to probenecid:

   • status epilepticus
   • blood dyscrasias
   • under 2 years-of-age
   • coadministration of salicylates
   • renal dysfunction or urate kidney stones
   • hypersensitivity to probenecid
5. Contraindications to N-acetylcysteine: hypersensitivity to N-acetylcysteine
6. Family unwilling to consent

• National Institutes of Health (NIH)
• National Institute of Neurological Disorders and Stroke (NINDS)