Studies have confirmed [39] that excessive glutamate is associated with seizures and that the glutamic acid → N-methyl-D-aspartate (NMDA) receptor → cyclooxygenase-2 (COX-2) → prostaglandin E2 receptor → P-gp pathway is involved in the regulation of P-gp expression in epilepsy (Figure 2). The gene discussed is PTGS2; the disease is epilepsy.