Orgaran (Org 10172) or heparin for preventing venous thrombosis after elective surgery for malignant disease? A double-blind, randomised, multicentre comparison. ANZ-Organon Investigators' Group.

This double-blind, randomised, multicentre trial in 513 patients having elective surgery for intra-abdominal or intrathoracic malignancy compared the efficacy and safety of venous thrombosis (VT) prophylaxis using 750 anti-factor Xa units of Orgaran (a mixture of low molecular weight heparinoids) given subcutaneously (sc) twice-daily with that of twice-daily injections of 5,000 units standard heparin. The main study endpoints were the development of postoperative VT detected by 125I-fibrinogen leg scanning, and the onset of clinically significant venous thromboembolism or bleeding. "Intent to treat" analysis showed a statistically non-significant trend towards less VT during Orgaran prophylaxis (10.4%) than after heparin (14.9%) and there was no difference in bleeding complications between the two study groups. Results remained similar if only patients who completed the intended course of therapy ("compliant patients") were analysed. Other trials have shown that Orgaran prevents VT after hip surgery and stroke. We now show it is also safe and effective in patients having major surgery for cancer.

Comparison of the effect of a conventional heparin and a low molecular weight heparinoid on platelet function.

In a study comparing the in vitro effects of heparin and a low molecular weight heparinoid (Organon 10172) on aggregation of platelets from normal subjects, we have demonstrated that whereas heparin markedly enhances platelet aggregation induced by other aggregators and inhibits the anti-aggregatory effect of epoprostenol (prostacyclin, PGI2), heparinoid does not produce such effects. The use of heparinoid may thus have a significant advantage over that of heparin in situations where enhanced platelet aggregation is the main factor leading to thrombosis or where heparin treatment is followed by thrombocytopaenia.