Overcoming Membrane Transporters to Improve CNS Drug Delivery - Improving Brain Antioxidants After Traumatic Brain Injury

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.

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