Effect of a new vasodilator (flunarizine) on the cerebral circulation

In order to clarify the effects of flunarizine, a newly-synthesized derivative of piperazine on cerebral circulation and metabolism, cerebrocortical oxygen tension, carbon dioxide tension and cerebrocortical blood flow were continuously recorded, along with a simultaneous monitoring of arterial blood pressure in 11 cats. Maximal changes in cerebrocortical oxygen tension induced by intravenous administration of flunarizine (0.6-1.0 mg/kg) were compared with those of papaverine hydrochloride (1 mg/kg). Flunarizine caused increases in cerebrocortical oxygen tension as well as cerebrocortical blood flow and a decrease in cerebrocortical carbon dioxide tension despite a fall in blood pressure, indicating an increase of cerebral blood flow presumably due to cerebral vasodilatation. Since the increase of cerebrocortical oxygen tension induced by flunarizine was comparable to that induced by papaverine, it was concluded that flunarizine appears to be a potent vasodilator of cerebral vessels.