Recombinant Factor VIIa: clinical applications for an intravenous hemostatic agent with broad-spectrum potential

Use of Activated Factor VII in Patients with Diffuse Alveolar Hemorrhage: A 10 Years Institutional Experience

INTRODUCTION

Diffuse alveolar hemorrhage (DAH) is a life-threatening condition with an obscure etiology and pathogenesis. It is associated with many drugs and diseases including chemotherapy, hematopoietic stem cell transplantation, and autoimmune disorders. This retrospective study reports our experience with 23 patients who had DAH and received intravenous recombinant activated Factor VIIa (rFVIIa).

METHODS

We performed a retrospective chart review of patients who received intravenous rFVIIa for DAH at a tertiary care university hospital between January 1, 2003 and May 31, 2013. We report demographics, etiology of DAH, frequency and total dose of intravenous rFVIIa, effect of rFVIIa on DAH, and morbidity and mortality.

RESULTS

Mean age was 47 ± 19 years. There were 13 men and 10 women. Nine patients had Anti-neutrophil cytoplasmic antibody (ANCA) vasculitis, two had systemic lupus erythematosus, three had Good pasture's syndrome, seven were post-bone marrow transplant, one had idiopathic thrombocytopenic purpura, and one had cryoglobulinemia. Treatment in the ICU was required for 22 patients of whom 18 were intubated and on mechanical ventilation; one patient was treated on general medical service. All patients received 35-120 mcg/kg rFVIIa every 2 h until hemostasis was achieved or treatment was judged to be inadequate. In 22/23 patients, bleeding resolved with rFVIIa therapy. The mean dose to control bleeding was 5 ± 3 mg. Eight patients died (36 %) of their underlying condition; six of them had received bone marrow transplant, while two had ANCA vasculitis. Deaths were due to multiorgan failure, sepsis, and progressive underlying disease. No overt, clinically obvious adverse thrombotic events were observed with the use of rFVIIa.

CONCLUSION

Activated Factor VII can achieve hemostasis in patients with diffuse alveolar hemorrhage.

Monitoring drug safety with registries: useful components of postmarketing pharmacovigilance systems

OBJECTIVE

At the time of licensing by regulatory agencies, the full range of risks and possible adverse drug reactions associated with a medication is rarely fully realized. This commentary aims to describe the role of registries as useful components of postmarketing pharmacovigilance systems for monitoring highly specialized medications associated with significant financial costs.

STUDY DESIGN AND SETTING

We consider the limitations of traditional pharmacovigilance programs and discuss the strengths, limitations, and uses of registries in postmarketing pharmacovigilance systems.

RESULTS

Registries have become increasingly appealing in postmarketing surveillance of medications; however, their exact role continues to evolve. Key registry projects, including the Prospective Immunogenicity Surveillance Registry, British Society for Rheumatology Biologics Register, Australian Rheumatology Association Database, the Haemostasis Registry, and the Bosentan Patient Registry highlight the value of registries for monitoring the incidence of rare adverse events.

CONCLUSION

Although often limited by lack of a control group and the need for complete case ascertainment to maintain data integrity, registries are a useful component of postmarketing pharmacovigilance systems for monitoring highly specialized medications associated with significant financial costs.

Pharmacokinetics of recombinant activated factor VII in trauma patients with severe bleeding

INTRODUCTION

Recombinant activated factor VII (rFVIIa) has been used as adjunctive therapy in trauma patients with severe bleeding. However, its pharmacokinetics profile remains unknown.

METHODS

In two placebo-controlled studies in patients with blunt and penetrating trauma, the pharmacokinetics of rFVIIa given at an initial dose of 200 microg x kg-1 after transfusion of eight red blood cell units, followed by additional doses of 100 microg x kg-1, one and three hours later, have been studied, based on the FVII coagulant activity assay. Both non-compartment and population pharmacokinetic analyses were performed. A two-compartment, population pharmacokinetic model was used to estimate a population profile for the rFVIIa dosing regimen. Data are population means (percent coefficient of variation (CV)).

RESULTS

Based on the two-compartment population model, the estimated pharmacokinetic parameters were: clearance 40 (30% CV) ml x kg-1 x h-1; central volume of distribution 89 (32% CV) ml x kg-1; inter-compartmental clearance 24 ml x kg-1 x h-1; and peripheral compartment volume 31 ml x kg-1. Baseline FVII coagulant activity was estimated at 0.29 (39% CV) U x ml-1, initial half-life was 0.6 (34% CV) hours, and terminal half-life 2.4 (50% CV) hours. High intra- and inter-patient variability was noted in volume of distribution and clearance, which was in part correlated with the transfusion requirements as the single significant covariate. The non-compartmental analysis led to almost identical estimates of key parameters.

CONCLUSION

A high intra- and inter-patient variability was noted in the volume of distribution and clearance of rFVIIa in trauma patients with severe bleeding, mainly related with the transfusion requirements and thus blood loss and/or bleeding rate.

Management of bleeding emergencies: when to use recombinant activated Factor VII

Recombinant activated Factor VII (rVIIa) was originally released as a clotting factor, with use limited to a select group of patients who had few other treatment options. Due to the apparent ability of rVIIa to stop bleeding, no matter what the underlying cause, there is great interest in use of rVIIa in a wide range of bleeding patients. This article discusses rVIIa and its uses in a variety of patients, especially liver disease and trauma patients, and makes suggestions for appropriate use. Although most of the reports on rVIIa are anecdotes and case series, there is increasing data for clinical trials to help guide usage.

Mechanistic implications for the use and monitoring of recombinant activated factor VII in trauma

As interest in the use of activated recombinant factor VII (rFVIIa) in trauma grows, questions arise regarding how best to monitor rFVIIa therapy and when rFVIIa may be expected to improve hemostasis. Knowledge of the mechanisms of action may be combined with available data on laboratory monitoring and efficacy in various coagulopathic states in coming to clinically relevant conclusions. This review addresses the physiology of hemostasis, placing emphasis on how rFVIIa influences the process by both tissue factor dependent and tissue factor independent mechanisms. This is extended to a mechanistic consideration of how rFVIIa may function under acidotic, hypothermic, and hemodilutional and/or consumptive conditions of trauma related coagulopathy. When these considerations are viewed alongside the available clinical data, it becomes apparent that rFVIIa has potential to improve hemostasis during trauma coagulopathy, within limitations. Common laboratory procedures are discussed with reference to mechanisms of action of rFVIIa and the available clinical data. Although there is no single assay that can predict rFVIIa efficacy in trauma, the prothrombin time (PT) is recommended as a minimum. Although a shortened PT does not predict success, correction of PT into the normal range may be a better indicator. A nonresponding PT appears to indicate that rFVIIa alone will not lead to hemostasis, and that additional blood products and other measures must be applied. Once the patient is more stable, PT and thromboelastography are recommended.

A multicenter assessment of recombinant factor VIIa off-label usage: clinical experiences and associated outcomes

BACKGROUND

Off-label use of recombinant factor VIIa (rFVIIa) occurs despite minimal data. The purpose of this study was to describe prescribing practices and clinical outcomes for off-label rFVIIa use.

STUDY DESIGN AND METHODS

A retrospective, multicenter chart audit of 315 nonhemophiliac patients was performed.

RESULTS

Off-label indications included prevention of bleeding primarily related to procedural manipulation in 37.8 percent of patients and treatment of bleeding in 62.2 percent of patients. Baseline coagulopathy was present in 79.7 percent of patients. Prescriber specialty varied. The median doses for prevention and treatment were 75.6 and 89.4 microg per kg, respectively (p = 0.0006). The international normalized ratio (INR) decreased (p < 0.0001) from baseline in both groups. Transfusions of blood products were provided to 85.1 percent of patients before rFVIIa administration with considerable practice variation. Few patients received other procoagulant agents. In the prevention group, 14.3 percent of patients bled within 6 hours of their procedure. No variable was independently associated with bleeding prevention. In the treatment group, 52.6 percent of patients stopped bleeding within 6 hours of rFVIIa administration. The only independent variable associated with bleeding cessation was an arterial pH value of less than 7.20, which was a negative predictor (odds ratio, 0.207; 95% confidence interval, 0.084-0.507). Possible rFVIIa-associated adverse events occurred in 9.8 percent of patients and primarily involved undesirable clotting. No variable was independently associated with adverse events.

CONCLUSIONS

Off-label use of rFVIIa includes prevention and treatment of bleeding. rFVIIa is associated with INR reduction. Bleeding is rare with prophylactic rFVIIa but the cessation of bleeding is less than reported in the literature and may be related to pH. Possible adverse events are related to undesirable clotting.

Cerebral blood flow mapping in two different subtypes of intraparenchymal hemorrhagic traumatic lesions

The pathogenesis and the viability of edematous tissue may be different in traumatic hematomas and traumatic contusions. We tested the hypothesis that mapping of regional Cerebral Blood Flow (rCBF) was different in these two subtypes of traumatic intraparenchymal lesions. We evaluated rCBF by means of Xenon-enhanced computerized tomography (Xe-CT) in 59 traumatic intracerebral lesions from 43 patients with severe head injury. One-hundred-nine intracerebral lesions/Xe-CT CBF measurements were obtained. The rCBF was measured in the hemorrhagic core, in the intralesional oedematous low density area and in a 1 cm rim of apparently normal perilesional parenchyma of both lesion subtypes. Not statistically significant lower rCBF levels were found in the edematous area of traumatic contusions. In traumatic hematomas rCBF levels were lower in the core than in the low density area, suggesting that rCBF in edematous area is marginally involved in the initial traumatic injury and that edema is probably influenced by the persistence of the hemorrhagic core. Conversely, in the traumatic contusions a difference in rCBF values was found between core, low density area and perilesional area, indicating that rCBF of the low density area is related to a concentrical distribution of the initial injury.