The influence of low molecular weight heparin in combination with dihydroergotamine on experimental thrombosis and haemostasis.

The influence of low molecular weight heparin in combination with dihydroergotamine (DHE) on thrombus formation and primary haemostasis was investigated in rabbit models. Conventional heparin in the dose of 60 units anti Xa activity/kg b. w. effectively prevented thrombus formation but the same dose of a low molecular weight fragment only gave a marginal decrease of the frequency of thrombosis. The thrombus weight was, however, significantly reduced. Doubling the dose of the heparin fragment totally abolished thrombus formation as did the combination of 60 units with DHE. With DHE it was also possible to diminish the low molecular weight heparin dose to 30 units with a good prophylactic effect. There was a small but significant increase of haemostatic plug formation time in all treatment groups except the one with low molecular weight heparin fragment 30 units anti Xa activity combined with DHE. Thus, by combining low molecular weight heparin in a low dose with DHE it is possible to prevent thrombus formation without influencing primary haemostasis in rabbits.