: To test the a priori hypothesis that amantadine reduces irritability ( primary hypothesis ) and aggression ( secondary hypothesis ) among individuals greater than 6 months post-TBI METHODS : : A total of 76 individuals greater than 6 months post-TBI referred for irritability management were enrolled in a parallel-group , randomized , double-blind , placebo-controlled trial of amantadine ( n = 38 ) versus placebo ( n = 38 ) .