However, because brain concentration of pioglitazone is limited by P-glycoprotein, a drug efflux transporter, and (+)-pioglitazone is more resistant to this efflux transporter and accumulates in higher concentrations in the brain tissue than (−)-pioglitazone does [8], this stereoselectivity on brain penetration of pioglitazone may help develop more efficient compound of pioglitazone to be used as a preventive or therapeutic agent for dementia. The gene discussed is ABCB1; the disease is dementia.