Final answer:
The appropriate treatments for preventing thrombosis in a patient with heparin-induced thrombocytopenia are Fondaparinux or direct oral anticoagulants (DOACs), as these do not exacerbate the condition. Warfarin should not be used until the patient's platelet count has normalized due to its potential to cause a hypercoagulable state.
Step-by-step explanation:
The treatment for preventing thrombosis in patients with heparin-induced thrombocytopenia (HIT) should avoid heparin-based products because of the immune-mediated adverse reaction that patients with HIT have developed. Instead, alternative anticoagulants should be used. Fondaparinux is a synthetic and selective inhibitor of Factor Xa that has been shown to be effective in treating HIT without causing a further drop in platelet count. Additionally, direct oral anticoagulants (DOACs) such as rivaroxaban (Xarelto), dabigatran (Pradaxa), and apixaban (Eliquis) can be considered since they have different mechanisms of action and are not associated with HIT. Warfarin should not be initiated until the platelet count has recovered, as it may transiently worsen HIT by decreasing protein C activity more quickly than coagulation factor activity and potentially lead to a hypercoagulable state. Therefore, the answer would be either C) Fondaparinux or D) Direct oral anticoagulants (DOACs), depending on the specific clinical circumstances and after careful consideration of the risks and benefits.