Dixyrazine, a phenothiazine derivative, can prevent brain oedema induced by intracarotid injection of protamine sulphate. In Vivo: Pretreatment with Dixyrazine 10 mg/kg completely prevents the brain oedema and significantly reduces the albumin increase in cerebrospinal fluid (CSF)^[1]. The phenothiazine Dixyrazine (5 mg/kg i.v.) has minimal, transient hypotensive effects but significantly reduces the leakage of ¹²⁶I labelled serum albumin in conscious rats subjected to acute hypertension provoked by i.v. Adrenaline or Bicuculline. The diameters of pial arteries and veins are continuously measured with a multichannel videoangiometer through a closed cranial window in anesthetized rats before and after i.v. injection of Dixyrazine (5 mg/kg). Dixyrazine, 5 mg /kg, induces a slight transitory decrease in blood pressure (10-20 mm Hg). Maximum MAP is slightly but not significantly lower in Dixyrazine-treated rats^[2].