Effects of an oral antidiabetic drug on the fibrinolytic system of blood in insulin-treated diabetic patients.

Selected variables of the fibrinolytic system were assessed in 23 men with insulin-treated diabetes with no measurable pancreatic beta-cell function. Gliclazide, a second-generation sulphonylurea drug, was administered to the patients over a period of 6 months in daily doses of 160 mg or 240 mg, and blood samples were obtained before, during, and after treatment. Determined by global assays, the drug did not significantly change plasminogen activator activities in euglobulins. Measurements of specific components of the system of fibrinolysis showed a marginal increase during administration of gliclazide of tissue-type plasminogen-activator antigen and prekallikrein activity in plasma, whereas the activities in euglobulins of the intrinsic plasminogen proactivators remained nearly the same during the study. Levels in plasma and euglobulin of C1-inactivator antigen and in plasma of factor XII antigen and t-PA inhibition capacity remained constant throughout the study. There were no changes of the increase in concentration of t-PA activity and t-PA antigen following venous occlusion. The metabolic state remained the same during the whole study. It is concluded that gliclazide induces small, but significant, non-insulin-dependent extrametabolic effects on the extrinsic (t-PA) and intrinsic (prekallikrein) system of fibrinolysis. Whether these changes are of physiological importance remains to be demonstrated.