ABCB1 and epilepsy: In 2003, Siddiqui et al.[28] reported the C3435T polymorphism in the ABCB1 gene as being associated with resistance to multiple AEDs, and leading to the suggestion, for the first time, that drug resistance in epilepsy might be genetically determined.[28] The study was a retrospective case–control study that compared the frequencies of the ABCB1 C3435T variant in 115 AED responders, with 200 AED-resistant patients and 200 nonepileptic controls.