- For this pilot study, the investigators will diverge slightly from the above WHO definition of mild TBI and exclude patients who report a history of seizures for this investigation. Although no seizures have been reported to the FDA in relationship to pregnenolone use, pregnenolone could theoretically influence seizure threshold if metabolized to its sulfated derivative, which demonstrates negative modulatory actions at GABAA receptors. Since the preliminary data suggest that pregnenolone administration increases the GABAergic neuroactive steroid allopregnanolone five-fold, however, and since allopregnanolone demonstrates marked anticonvulsant activity in a number of animal seizure models, this theoretical risk may be small or non-existent.