[Thrombolytic agents: efficacy in relation to evolution time and dose]

"In vitro" efficacy of urokinase (UK), streptokinase (SK) and tissue-type plasminogen activator (t-PA) was studied. Lytic action was measured by dry clot weight, 125I counts released from previously incorporated 125I-fibrinogen and fibrin fragment quantification at 1, 3 and 7 days using different doses. t-PA doses between 100 and 0.8 IU/ml were efficient. t-PA (40 IU/ml), SK (200 IU/ml) and UK (200 IU/ml) showed an equivalent activity in 1, 3 and 7 day-old clots. Fibrin fragment (D-D dimer) production was highest when t-PA and UK were used. "In vitro" lytic capacity up to 7 days after clot formation has been proved with the different fibrinolytic agents.