ABSTRACT
A number of technical and clinical conditions reportedly associated with diazepam-related thrombophlebitis were investigated. Diazepam alone and in combination with fentanyl and methohexital was administered intravenously to 519 healthy, predominantly young adult patients undergoing routine oral surgery for removal of third molars. Indirect evidence is provided to show that two slightly different vasculopathies are involved: thrombophlebitis, in which pain and induration are both present but in which there is a slight delay in the time of inception of the condition; and phlebothrombosis, in which the reaction is almost immediate but pain is not significant and induration of the vein is the predominant feature. The overall incidence was 2.3% for thrombophlebitis and 9.8% for phlebothrombosis. There were four significant variables associated with phlebothrombosis: use of tobacco, use of oral contraceptives, multiple injections of diazepam, and pain during injection. The only significant variable associated with thrombophlebitis was the site of injection.