Effect of furosemide on plasma fibrinolytic activity and urokinase excretion.

Plasma fibrinolytic activity, as measured by the fibrin-plate method, is enhanced after a single intravenous administration of 40 mg of furosemide. This effect becomes evident within 30 min and a peak response is attained 6 h after i.v. administration. On successive administration of furosemide, the fibrinolytic effect persists and the second peak becomes manifest again after 6 h. Following the parenteral administration of furosemide there is an initial decrease of urinary urokinase excretion which returns to a normal level after 3 to 6 h. Possible mechanisms which may explain the enhanced fibrinolytic activity after furosemide administration are discussed.