Histopathology of veins after intravenous lorazepam and RO 21-3981

A previously established rat model has been utilized to demonstrate that an acute inflammatory response occurs after high intravenous doses of lorazepam. This occurs only with high concentrations of drug equivalent to 20 times the normal clinical dosage in man. In contract, water soluble RO 21-3981 produces no vascular pathology in any dosage evaluated. It appears that propylene glycol may play a role in the pathogenesis of the intravascular injury observed.