Preclinical safety evaluation of low molecular weight heparin-deoxycholate conjugates as an oral anticoagulant

The preclinical safety of a newly developed oral anticoagulant, the low molecular weight heparin-deoxycholate conjugate (OH09208), was evaluated by a comprehensive evaluating program in compliance with standard guidelines. The single dose oral toxicity study in rats receiving 2000 and 5000 mg kg(-1) of OH09208 did not reveal any mortality, unusual body weight changes or necropsy findings. The results of the 4-week oral toxicity study with a 4-week recovery program in rats receiving OH09208 in doses of 100, 300 and 1000 mg kg(-1) day(-1) did not reveal any mortality, or indicate any unusual clinical signs, or show any toxicokinetic relationships to the administration of OH09208. Although the increase in liver enzymes in one male dog treated with 300 mg kg(-1) day(-1) and one female dog treated with 1000 mg kg(-1) day(-1) could not be excluded from the effect of the test substance, no other toxicologically significant changes were observed in the 4-week oral toxicity study with a 4-week recovery in beagle dogs. Thus, while the no-observed-adverse-effect level value from the 4-week study in both male and female rats was 1000 mg kg(-1) day(-1), those from the 4-week study in male and female beagle dogs were 300 and 1000 mg kg(-1) day(-1), respectively. Furthermore, OH09208 did not induce anaphylactic reactions in guinea pigs, micronucleated bone marrow cells in male ICR mice, chromosomal aberration in Chinese hamster lung cell lines, bacterial reverse mutation, and any abnormalities in hERG current assay, mouse central nervous system and dog cardiovascular studies. Overall, there were no unexpected toxicities in this preclinical study that might have precluded the safe administration of OH09208 to humans.

Oral thromboprophylaxis following total hip or knee replacement: review and multicentre experience with dabigatran etexilate

The risk of venous thromboembolism (VTE) in patients undergoing total knee or hip replacement surgery is high. As a result, thromboprophylaxis is highly recommended. While current thromboprophylactic agents, such as low molecular weight heparins (LMWH) and vitamin K antagonists, are safe and effective their use can be problematic. Therefore, there is a need for alternative anticoagulants that are as safe and effective as conventional agents, but are more convenient and easier to use. Dabigatran etexilate, a direct thrombin inhibitor, is one such anticoagulant. For VTE prevention following major orthopaedic surgery, dabigatran etexilate shows similar efficacy and safety to the LMWH enoxaparin, and is approved for use in more than 75 countries, including Europe and Canada. Here, we summarize and discuss the experiences of four German clinics that have recently introduced dabigatran etexilate into clinical practice. Overall, dabigatran etexilate was well received by patients, surgeons and nurses, and compared favourably with enoxaparin. Staff appreciated the oral, single-dose administration of dabigatran etexilate. Patient satisfaction was high, especially in those individuals who had previously used LMWHs. In this review, we also address a number of questions that were asked by patients or staff; this will be of relevance to orthopaedic surgeons and nurses. We conclude that, in these four German clinics, dabigatran etexilate offered an effective oral alternative to existing thromboprophylactic agents in patients undergoing major orthopaedic surgery.

Risk of heparin-induced thrombocytopenia in patients receiving thromboprophylaxis

Heparin-induced thrombocytopenia (HIT) is a clinicopathological syndrome associated with heparin therapy that is characterized by a decrease in platelet counts and/or the development of a new thrombosis. Two types of HIT exist, type I is nonimmune and self-resolves, whereas type II is immune-mediated and clinically important. The formation of antibodies against the platelet factor 4-heparin complexes results in platelet activation and thrombin formation, which lead to an increased risk of thrombosis. Unfractionated heparin is associated with a higher risk of HIT than low-molecular-weight heparins. Surgical patients, particularly those undergoing orthopedic or cardiac surgery, are at higher risk of HIT than medical patients. Treatment of HIT involves heparin cessation together with anticoagulation with direct thrombin inhibitors or indirect factor Xa inhibitors.

Review of the Relationship Between Venous Thromboembolism, Malignancy and Its Treatment

Venous thromboembolism is a common complication that develops in approximately 20% of patients with cancer. Presence of tumor and other risk factors, such as inflammation, surgery, obesity, and medications, have the potential to alter the intravascular coagulation homeostasis and lead to thrombosis. Although malignancy may predispose patients to venous thromboembolism, many chemotherapy agents also increase the risk. In this article, some of the agents tamoxifen, asparaginase, fluorouracil, thalidomide, lenalidomide, bevacizumab, and hematopoietic growth factors are discussed. Many patients will experience a thrombotic event despite optimal prophylaxis. Thus, this article will address the guidelines for treatment and prophylaxis of venous thromboembolism. In general, the venous thromboembolism risk should be assessed before certain antineoplastic regimens are prescribed to patients with cancer.