ABCB1 and epilepsy: However, in two studies in non-Caucasian subjects, the association was in the reverse direction compared with studies in Caucasian subjects, in that patients with drug-resistant epilepsy were more likely to have the TT genotype compared with those with drug-responsive epilepsy,[31, 32] highlighting the complexity of the possible role of ABCB1 polymorphisms in AED response in different ethnic populations.