There is considerable evidence that the quantity or quality of plasma
lipids influences platelet function tests, and
clofibrate reduces high plasma
lipids and alters some platelet tests.
Clofibrate was accordingly given to patients with
vascular disease who were at risk of
thrombosis. The
heparin thrombin clotting time (HTCT), initially short and thus possibly reflecting increased activation, was regularly returned to normal after about a month's delay. The
fibrinogen was also normalized but the initially abnormal anti-thrombic activity became more abnormal.
ICI 55,897, an analogue of
clofibrate, also normalized the HTCT and the
fibrinogen and had no adverse effect on the anti-
thrombin levels. This compound has no effect on plasma
lipids. If it can be shown that the correction of abnormal tests conveys clinical benefit these findings suggest that
ICI 55,897 might clinically be more beneficial than
clofibrate. However, direct comparison of
clofibrate and
ICI 55,897 suggests that
clofibrate is more effective in normalizing the HTCT. The mechanism underlying these
drug-induced changes are unknown but they cannot be directly related to
lipid changes.