PD 168568 is a dopamine D4 receptor antagonist (Ki = 8.8 nM). It is selective for dopamine D4 over D2 receptors (Ki = 1,842 nM). PD 168568 (3 mg/kg) reverses amphetamine-induced hyperlocomotion in rats. It also inhibits the growth of glioblastoma neural stem cells when used at concentrations of 25 and 50 µM.