Urokinase Pulmonary Embolism Trial

To the Editor.— A 12-hour infusion of urokinase was shown to accelerate the resolution rate of pulmonary thromboemboli more than did a similar infusion of heparin (214:2163, 1970). However, "... urokinase regimen did not usually achieve complete thrombolysis...." The lack of dramatic thrombolysis may well be ascribed to the short duration of the urokinase infusion. In a study of treatment of acute thrombophlebitis of the deep iliac, femoral, and leg veins with streptokinase, Widmer¹et al showed that it was necessary to infuse the agent for as long as three to seven days in a majority of the patients treated. The conclusions of that study were based exclusively on phlebography, rather than upon unreliable clinical signs only. Discontinuation of the streptokinase infusion was effected only after complete thrombus resolution had been found on phlebography, after laboratory tests had shown a considerable decrease in the activity of the fibrinolytic system,