ABCB1 and epilepsy: The adjacent nonepileptic tissue from the same patients did not show elevated expression of the transporter.[24] In 2003, Siddiqui et al.[25] 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.