Hello, sintrom and clexane are considered equally efficient in preventing thrombosis. Sintrom is usually preferred mostly because clexane is much more expensive. Clexane is easier to use (if you don t mind the injections) because it has a stable effect on coagulation. Sintrom s effectiveness may vary depending on very many factors and needs close monitoring of the INR. If your INR drops below target levels, you re in danger of thrombosis. If your INR gets very high (particularly if 4-5) then you re in danger for bleeding. Sintrom - when monitored - is usually safe enough. You haven t mentioned your sex. Females that may become pregnant should avoid sintrom. If you ve got antiphospholipid syndrome then perhaps you should discuss with your treating physician about aspirin too! I hope I ve helped! If you d like more information, please let me know! Kind Regards!