Inhibitors of fibrinolysis in the treatment of haemophilia

A review of hyperfibrinolysis in cats and dogs

The fibrinolytic system is activated concurrently with coagulation; it regulates haemostasis and prevents thrombosis by restricting clot formation to the area of vascular injury and dismantling the clot as healing occurs. Dysregulation of the fibrinolytic system, which results in hyperfibrinolysis, may manifest as clinically important haemorrhage. Hyperfibrinolysis occurs in cats and dogs secondary to a variety of congenital and acquired disorders. Acquired disorders associated with hyperfibrinolysis, such as trauma, cavitary effusions, liver disease and Angiostrongylus vasorum infection, are commonly encountered in primary care practice. In addition, delayed haemorrhage reported in greyhounds following trauma and routine surgical procedures has been attributed to a hyperfibrinolytic disorder, although this has yet to be characterised. The diagnosis of hyperfibrinolysis is challenging and, until recently, has relied on techniques that are not readily available outside referral hospitals. With the recent development of point-of-care viscoelastic techniques, assessment of fibrinolysis is now possible in referral practice. This will provide the opportunity to target haemorrhage due to hyperfibrinolysis with antifibrinolytic drugs and thereby reduce associated morbidity and mortality. The fibrinolytic system and the conditions associated with increased fibrinolytic activity in cats and dogs are the focus of this review article. In addition, laboratory and point-of-care techniques for assessing hyperfibrinolysis and antifibrinolytic treatment for patients with haemorrhage are reviewed.

The hemophilias and their clinical management

Outcomes for patients with hemophilia have improved dramatically over the past 50 years. With the increased availability of safe clotting factor concentrates, the primary focus in clinical management is now the prevention of long-term complications, most notably the debilitating hemophilic arthropathy that is associated with severe disease. This article reviews evidence-based approaches for managing both children and adults with hemophilia. Definitive evidence of improved clinical results from primary prophylaxis started in young patients with severe hemophilia A and a minimal bleeding history is presented. Furthermore, recent studies showing benefits for initiating prophylaxis in older adolescents and adults with established joint disease are examined. Inhibitors to factor VIII are the most problematic complication of factor replacement therapy. Patient-specific and treatment-related factors that contribute to the risk of inhibitor formation are discussed and controversies and clinical evidence related to approaches for tolerance induction are reviewed.

Distribution of tranexamic acid to plasma and saliva after oral administration and mouth rinsing: a pharmacokinetic study

The objective of the study was to investigate the content of tranexamic acid in plasma and in mixed, unstimulated whole saliva after oral administration and mouth rinsing. Ten healthy volunteers each received 1 g of tranexamic acid orally, whereas 20 healthy volunteers rinsed their mouths with 10 mL of a 5% aqueous tranexamic acid solution for two minutes. Blood and saliva were collected 30, 60, 120, 240, 360, and 480 minutes after administration of tranexamic acid. Samples of blood and saliva were analyzed for tranexamic acid content by electron capture gas chromatography. After oral administration, the mean plasma concentration of tranexamic acid reached its maximum after 120 minutes at approximately 7 micrograms/mL, whereas none of the saliva samples contained tranexamic acid at detectable levels. After mouth rinse, the plasma concentrations remained below 2 micrograms/mL, whereas the concentrations found in saliva initially were very high (after 30 minutes mean concentration above 200 micrograms/mL) and remained at a therapeutic level for more than two hours. These findings indicate, that fibrinolysis in the oral cavity can be inhibited only by local administration of tranexamic acid. This finding may be of significance when the drug is used for prevention and treatment of bleeding in the oral cavity in patients with coagulation defects.

Effect of local antifibrinolytic treatment with tranexamic acid in hemophiliacs undergoing oral surgery

The objectives of the present clinical investigation were to examine the effects in hemophiliacs of local antifibrinolytic treatment with tranexamic acid on the incidence of postoperative bleeding after oral surgery and on the amount of replacement therapy needed to control bleeding. The study compared three groups of patients. The patients in group A received high doses of factor concentrate and systemic antifibrinolytic treatment with tranexamic acid. In group B local antifibrinolytic treatment with tranexamic acid was added to the treatment received by group A. Group C received replacement therapy to raise factor levels to approximately 10% of the normal value perioperatively, combined with systemic and local antifibrinolytic treatment (mouth rinse) with tranexamic acid. The study demonstrated that local antifibrinolytic therapy with tranexamic acid as a supplement to the currently used systemic therapy significantly reduces the incidence of postoperative bleeding. The results of the study further suggest that replacement therapy can be reduced during oral surgery in the hemophilic patient provided that local and systemic inhibition of fibrinolysis is instituted.