Sequential interleukin 3 and granulocyte-macrophage-colony stimulating factor therapy in patients with bone marrow failure with long-term follow-up of responses

BACKGROUND

Interleukin-3 (IL-3) and granulocyte-macrophage-colony stimulating factor (GM-CSF) have synergistic, hematopoietic growth-promoting activity in preclinical studies. Because of the paucity of effective therapies for patients with chronic bone marrow failure states, the authors studied the biologic activity of sequential IL-3/GM-CSF in such patients.

METHODS

IL-3 was given subcutaneously for 5 days (at escalating doses of 0.15 microg/kg, 0.3 microg/kg, 0.6 microg/kg, 1.2 microg/kg, 2.5 microg/kg, 5.0 microg/kg, 10.0 microg/kg, or 15.0 microg/kg per day), and GM-CSF for was given subcutaneously for 9 days (at a dose of 5 microg/kg per day; Phase I 3 + 3 design) followed by 14 days of rest (total, 2 courses), then maintenance therapy.

RESULTS

The majority of 38 evaluable patients had aplastic anemia or myelodysplastic syndrome. Most patients (79%) had neutrophil responses. Ten patients (26%), all of whom were treated with IL-3 doses >/= 1.2 microg/kg per day, had platelet responses, with a median increase of 132 x 10(9)/L (range, 41-180 x 10(9)/L) over baseline in responders. Six patients (16%) had trilineage recovery, which could be durable (the longest ongoing at 6.5 years after therapy completion). The most common toxicities were low-grade fever, headache, and fatigue. The maximum tolerated doses were IL-3 at 10 microg/kg per day and GM-CSF at 5 microg/kg per day.

CONCLUSIONS

Sequential IL-3/GM-CSF effectively raised blood counts in some patients with bone marrow failure at doses that were tolerated well. These results indicate that early-acting growth factors can induce durable, multilineage responses in a subset of individuals with bone marrow failure.

Anaphylactic and anaphylactoid reactions associated with lepirudin in patients with heparin-induced thrombocytopenia

BACKGROUND

Lepirudin (Refludan) is a hirudin derivative. It is a direct thrombin inhibitor obtained by recombinant technology from the medicinal leech and is approved for treatment of heparin-induced thrombocytopenia complicated by thrombosis. Because 3 cases of fatal anaphylaxis possibly associated with use of lepirudin have been reported, we initiated an investigation of putative lepirudin-associated anaphylaxis.

METHODS AND RESULTS

Aided by the manufacturer (Schering AG, Berlin, Germany), we used the lepirudin study databases to identify all patients in whom possible anaphylaxis/severe allergy was recorded from 1994 to September 2002. The 26 possible cases identified were reviewed independently by 2 investigators. After excluding patients with mild skin reactions, reactions likely caused by concomitant medications, poorly documented cases, and reactions that did not correspond temporally with lepirudin use, there remained 9 patients judged to have had severe anaphylaxis in close temporal association with lepirudin. All reactions occurred within minutes of intravenous lepirudin administration, with 4 fatal outcomes (3 acute cardiorespiratory arrests, 1 hypotension-induced myocardial infarction). In these 4 cases, a previous uneventful treatment course with lepirudin was identified (1 to 12 weeks earlier). We recorded high-titer IgG-anti-lepirudin antibodies in an additional patient with anaphylaxis. Because lepirudin has been used in approximately 35 000 patients, the risk of anaphylaxis is approximately 0.015% (5 of 32 500) on first exposure and 0.16% (4 of 2500) in reexposed patients (7.5% estimated reexposures).

CONCLUSIONS

Lepirudin can cause fatal anaphylaxis, particularly in patients who are treated within 3 months of a previous exposure. The overall risk/benefit assessment of lepirudin as a treatment for heparin-induced thrombocytopenia remains favorable.

Benefit-risk assessment of treatments for heparin-induced thrombocytopenia

Patients with heparin-induced thrombocytopenia (HIT) are at high risk of thrombosis and should be treated with alternative anticoagulant therapy to reduce complications. The current treatment of choice is one of the approved direct thrombin inhibitors, argatroban or lepirudin. These drugs have been proven to be safe and effective in multicentre clinical trials where dosage regimens have been established for prophylaxis and treatment of thrombosis. Argatroban has also been tested and approved for use in invasive cardiology procedures in the HIT patient. Dosage regimens for other clinical uses, such as cardiac surgery, have not yet been established for either drug. The safety and effectiveness of the thrombin inhibitors is dependent on their use according to established guidelines. Other treatment options that may be effective for the patient with HIT include dextran, plasmapheresis, intravenous gammaglobulin and aspirin (acetylsalicylic acid). Although used historically, these options have not been tested in rigorous clinical trials. For life- and limb-threatening thrombosis, thrombolytic agents and/or surgery may provide benefit. Because the risk of bleeding is high from these procedures, they should be performed only by an experienced practitioner. Several studies have shown that patients with HIT requiring continued anticoagulation are best managed with a warfarin derivative initiated while under full anticoagulation with a thrombin inhibitor. There is a risk of skin necrosis and bleeding if guidelines for dose administration and monitoring of warfarin are not followed. Subsequent use of heparin or a low molecular weight heparin after resolution of the clinical episode of HIT can be hazardous, particularly within the first 3 months. If laboratory testing is negative, heparin may be cautiously reinstituted for short-term use (1-2 hours) with monitoring for platelet count decrease and thromboembolism. The pregnant patient with HIT requiring anticoagulation represents a particular challenge, where there is no drug of choice at present. Although today there are realistic treatment options for the patient with HIT, the morbidity and mortality associated with this disease have not been eliminated. Awareness and early treatment of HIT remain important components of the clinical care for patients exposed to heparins. Future therapeutic developments based on a better understanding of the pathophysiology of HIT may further improve clinical outcomes. Despite some limitations, the current treatment options for patients with HIT provide unparalleled benefit compared with the treatment options available only a few years ago.

Feto-maternal alloimmune thrombocytopenia due to HPA-5b incompatibility: a case report

Feto-maternal alloimmune thrombocytopenia (FMAIT) results from the maternal production of antibodies against fetal platelets with incompatible antigens inherited from the father. We present a case where this condition was diagnosed prenatally without previously affected siblings. The severe fetal thrombocytopenia was due to anti-HLA-5b maternal alloantibodies. This was treated successfully by intravenous immunoglobulins. Our case reflects that FMAIT due to anti-HPA-5b may be severe and may be corrected successfully with intravenous immunoglogulins.

Clinical utility of subcutaneous hirudins

The clinical utility of subcutaneous hirudins is discussed. The term "hirudins" refers to a class of antithrombotic agents structurally derived from the medicinal leech salivary protein hirudin. Breakthroughs in biotechnology over the past 20 years have resulted in the development of recombinant versions of hirudin (r-hirudin). Lepirudin is one such r-hirudin that is identical to natural hirudin except for the substitution of leucine for isoleucine at the N-terminus and the elimination of a sulfate group on the tyrosine at position 63. Another r-hirudin, desirudin, is identical to hirudin except for a valine-valine in the N-terminus and the absence of the sulfate group on tyrosine at position 63. Both r-hirudins are bivalent and tightly bind to both the catalytic site and the exposite of thrombin to exert their inhibitory effects on thrombin. Unfractionated heparin (UF) and low-molecular-weight heparins (LMWHs) are widely used in medical and surgical patients to prevent and treat arterial and venous thrombotic events. Besides bleeding, the major adverse effect of heparins is heparin-induced thrombocytopenia (HIT). HIT is associated with a paradoxical hypercoagulable state and marked risk of clinical thrombosis. Management of HIT requires the immediate cessation of all heparin exposure, and the initiation of an alternative anticoagulant. Because r-hirudins are effective agents and do not cross-react with HIT-associated antibodies, they are excellent anticoagulants in patients with past or current HIT. Clinical trials have also demonstrated the efficacy and safety of subcutaneous (s.c.) r-hirudins compared to heparins in non-HIT settings. Results of these trials support the use of r-hirudin therapy in patients with HIT or at risk of developing HIT. Additionally, case reports have described safe and effective use of s.c. r-hirudin therapy in the outpatient setting in both HIT and non-HIT patients.

Overview of heparin-induced thrombocytopenia

A brief overview of the pathophysiology, diagnosis, and treatment of heparin-induced thrombocytopenia (HIT) is discussed. Following any exposure to unfractionated heparin or low-molecular-weight heparin (LMWH), HIT, a serious allergic drug reaction, may occur. The frequency of HIT is thought to range from 1 to 5% of patients receiving heparin. This immune-mediated syndrome is paradoxically associated with thrombosis, not bleeding, with thrombin generation playing a central role. The diagnosis of HIT is based upon clinical findings that can be confirmed with laboratory assay; however, when there is clinical suspicion of HIT, all forms of heparin therapy should be immediately discontinued and initiation of alternative anticoagulation is strongly encouraged. In the presence of HIT, the use of LMWHs or initiation of warfarin without additional effective anticoagulation is not recommended. Argatroban and lepirudin, two direct thrombin inhibitors (DTIs), are approved by the Food and Drug Administration for the management of HIT. Both agents have been studied in the treatment and prevention of thrombotic events associated with HIT. Argatroban, a univalent inhibitor of thrombin, is eliminated via the liver, while lepirudin, the first DTI approved for HIT, is a bivalent thrombin inhibitor that is cleared by the kidneys. Neither argatroban nor lepirudin demonstrates cross-reactivity with heparin-induced antibodies, and both DTIs have been associated with effective anticoagulation and platelet recovery in patients with HIT. The appropriate use of DTIs in HIT reduces the risk of thrombotic events and severe consequences associated with this serious drug reaction.

Treatment options for heparin-induced thrombocytopenia

Appropriate management, as well as efficacy and safety, of heparin-induced thrombocytopenia (HIT) and prevention of severe consequences with argatroban and lepirudin are discussed. Heparin-induced thrombocytopenia, a serious immune-mediated drug reaction, can occur as an isolated incident (isolated HIT) or with acute thrombosis sometimes referred to as HIT and associated thrombosis syndrome (HITTS). Due to the severe consequences associated with HIT, appropriate management is critical. Argatroban and lepirudin, two direct thrombin inhibitors (DTIs), are currently FDA approved for use in patients with HIT. The clinical experience with these agents is critically examined in this article. The safety and efficacy of argatroban in management of HIT were the subject of a single published clinical trial. The study was designed to reflect conventional clinical practice, whereby treatment of patients with HIT was initiated upon clinical suspicion. In several of these patients, HIT antibodies could not be demonstrated. Compared to historical controls, argatroban demonstrated efficacy in patients with isolated HIT; however, no differences were observed in HIT patients with acute thrombosis. Rates of bleeding episodes did not differ between argatroban and control. The clinical efficacy and safety of lepirudin have been the subject of three clinical trials and one large drug monitoring program. Lepirudin has demonstrated benefit in HIT patients with or without existing thromboembolism. Bleeding rates were higher than in the historical control. However, bleedings requiring transfusion did not differ. Although no direct head-to-head comparison trials of argatroban and lepirudin have been conducted, parallels can be drawn between the agents based on careful review of published clinical trials. Consistently, rates of new thrombosis, limb amputation, and death appear to be lower in patients treated with lepirudin as compared with those treated with argatroban, whereas the risk for major bleeding per patient day seems to be similar with both DTIs.

Antimetastatic effect of tinzaparin, a low-molecular-weight heparin

The importance of coagulation activation in cancer patients is suggested by the clinical finding of hypercoagulability, experimental enhancement of metastasis and angiogenesis by coagulation factors such as tissue factor (TF) and thrombin and the possible antitumor effects of anticoagulant agents. Tinzaparin is a low-molecular-weight heparin (LMWH) with a relatively high molecular weight distribution and high sulfate to carboxylate ratio. In addition to its ability to inhibit thrombin and factor Xa, tinzaparin is particularly effective at releasing endothelial tissue factor pathway inhibitor (TFPI), the natural inhibitor of both procoagulant and non-coagulant effects of TF. The present study was undertaken to investigate the effect of tinzaparin on lung metastasis using a B16 melanoma model in experimental mice. Tinzaparin's anticoagulant effect in mice and its ability to release TFPI from human endothelial cells at various time points were demonstrated. Subcutaneous (s.c.) injection of tinzaparin (10 mg kg-1) 4 h before intravenous administration of melanoma cells (2.0 x 105) markedly (89%) reduced lung tumor formation (3 +/- 2) compared with controls (31 +/- 23; P < 0.001). In a second group of animals, tinzaparin (10 mg kg-1, s.c.) administered daily for 14 days following the initial (pretumor cell) dose, before assessment of lung seeding, reduced tumor formation by 96% (P < 0.001). No bleeding problems were observed in any of the tinzaparin-treated animals, despite a 4-fold prolongation of the whole blood clotting time after a single s.c. dose of tinzaparin (10 mg kg-1). Administration of tumor cells (2 x 106) caused a rapid and significant fall in platelet count 15 min after injection (a sensitive marker of intravascular coagulation) in controls (939 +/- 37 vs. 498 +/- 94 x 106 mL-1, P < 0.01), but this was prevented by tinzaparin treatment (921 +/- 104 x 106 mL-1). These data provide further experimental evidence to support the potential for LMWH as antimetastatic agents.

Autoimmune cytopenia does not predict poor prognosis in chronic lymphocytic leukemia/small lymphocytic lymphoma

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is characterized by an acquired immune defect that can cause autoimmune complications, including anemia and thrombocytopenia. We conducted an observational study of the epidemiology, clinical presentation and significance of autoimmune complications of CLL/SLL in 132 patients from a large population (>45,000 veterans), in which at least 90% of patients with CLL/SLL have been previously identified. Over a period of 12.5 years, 12 patients (9.1%) had autoimmune complications; of these, 6 (4.5%) had autoimmune hemolytic anemia (AIHA), 5 (3.8%) had immune thrombocytopenia (ITP), and 1 (0.8%) had pure red blood cell aplasia (PRBA). All 6 cases of AIHA had a positive direct immunoglobulin test for IgG and C3d. In 6 patients, CLL/SLL was an incidental finding at the time of presentation with autoimmune cytopenia. Nine out of 10 patients responded to immunosuppressive therapy, which was complicated by serious infection in 7 cases, one of which was fatal. The major cause of mortality in patients with autoimmune complications of CLL/SLL was secondary malignancy. Survival of patients with immune cytopenia was not significantly different from CLL/SLL patients without immune cytopenia. Among patients with anemia or thrombocytopenia, mortality was significantly higher in those with bone marrow failure compared to an autoimmune etiology. We show that in a non-referred population with a high incidence of CLL/SLL, autoimmune cytopenia can occur early in the natural history of the disease. These data suggest that the Rai and Binet classifications for CLL need to be modified for patients with autoimmune cytopenia. .

High-dose carboplatin, cyclophosphamide, etoposide with hematological growth factors, without stem cell support in patients with advanced cancer

PURPOSE

Peripheral blood progenitor cell (PBPC) transplantation, introduced into clinical practice to decrease the hematological toxicity of high-dose chemotherapy (HDCT), is both a costly procedure and a potential source of tumor cell reinfusion. The maximum tolerated dose of carboplatin (CB), cyclophosphamide (CT) and etoposide (VP) administered with growth factors without PBPC was determined in a previous phase I study. The aim of this phase II study was to evaluate the activity and toxicity of HDCT with CB, CT and VP administered with growth factors, without PBPC in a group of patients with advanced solid tumors.

PATIENTS AND METHODS

Forty patients with a median age of 52 years received two consecutive courses of chemotherapy every four weeks, consisting of CT 1500 mg/m2, VP 400 mg/m2 and CB AUC of 7-8. Following chemotherapy, hematological growth factors were administered for 14 days.

RESULTS

Grade 4 leukopenia and thrombocytemia occurred in 40 and 21 patients, respectively. An overall response rate of 72.5% was achieved. After a median 81 months follow-up, median time to progression and overall survival were 29 and 38 months, respectively.

CONCLUSION

These data indicate that HDCT chemotherapy may be delivered safely without PBPC support. Prolonged responses were observed in patients that had few therapeutic options.

Mycophenolate mofetil in the treatment of autoimmune HCV-associated haematological disorders showing steroid resistance or dependence

We report two cases of hepatitis C virus (HCV) associated autoimmune haematological disorders successfully treated with an unusual protocol (mycophenolate mofetil: MMF). The first case was a male patient with chronic HCV infection who developed, during interferon (IFN)/ribavirin therapy, severe autoimmune thrombocytopenia unresponsive to steroids. MMF was then administered and, simultaneously, the steroid dose was gradually reduced until withdrawal. Following this strategy, a progressive increase in platelet count and complete negativity of anti-PLT antibodies were achieved without changes in HCV-RNA quantitative determination. The second case was a woman with HCV liver cirrhosis with severe anaemia and Coombs test positivity partially responsive to continuous administration of steroid high doses. However, this treatment unmasked a severely painful vertebral osteoporosis. For this reason we introduced MMF and simultaneously steroid therapy was progressively reduced until withdrawal. Haemoglobin reached a normal value and the Coombs test became negative within 60 days. These case reports suggest that MMF may represent an interesting therapeutic approach for autoimmune HCV associated haematological disorders.

Heparin-induced thrombocytopenia: Pathophysiology and new treatment options

Heparin induced thrombocytopenia (HIT) is a severe complication of heparin therapy. It is generally accompanied by a paradoxical decrease in platelets leading to activation of platelets and of the coagulation system. HIT type I is a mild, transient, non-immune disorder. HIT type II is an immune-mediated reaction towards neo-antigen on PF4, which is platelet factor 4 (PF4) that is exposed upon binding to heparins. A low sulfated octasaccharide is required for binding to PF4. The generated immunoglobulines bridge platelets by binding to the FcgRIIa-receptor. In patients with HIT type II heparin/LMW-heparin has to be discontinued immediately upon clinical suspicion. Diagnosis can be confirmed by laboratory tests. As patients are at high risk for or because they have developed thromboembolism, anticoagulation is mandatory, despite thrombocytopenia. Treatment options are danaparoid, r-hirudin, bivalirudin, argatroban, dextransulfate, and dermatansulfate. In future, fondaparinux and ximelagatran may be considered for treatment.

Argatroban anticoagulation in patients with heparin-induced thrombocytopenia

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is an intensely prothrombotic syndrome managed by discontinuation of heparin therapy and substitution of an alternative inhibitor of thrombin. We describe our experience with argatroban, a direct thrombin inhibitor, in patients with HIT or HIT with thrombosis (HITTS).

METHODS

In this multicenter, nonrandomized prospective study, 418 patients with HIT were administered intravenous argatroban, 2 micro g/kg per minute, adjusted to maintain the activated partial thromboplastin time at 1.5 to 3 times the baseline value for a mean of 5 to 7 days. Comparisons were made with a historical control cohort (n = 185). The prospectively defined, primary efficacy end point was a composite of all-cause death, all-cause amputation, or new thrombosis in 37 days. Other end points included the components of the composite, death due to thrombosis, increased platelet count, and bleeding.

RESULTS

In the HIT arm, the composite end point was significantly reduced in argatroban-treated patients vs controls (28.0% vs 38.8%; P =.04). In the HITTS arm, the composite end point occurred in 41.5% of argatroban-treated patients vs 56.5% of controls (P =.07). By time-to-event analysis of the composite end point, argatroban therapy was significantly better than historical control therapy in HIT (P =.02) and HITTS (P =.008). Argatroban therapy also significantly reduced new thrombosis in HIT and HITTS and death due to thrombosis in HITTS. There were no significant between-group differences in all-cause death or amputation. Platelet counts recovered more rapidly in argatroban-treated patients than in controls. Bleeding rates were similar between groups.

CONCLUSION

Argatroban therapy, compared with historical control, improves outcomes, particularly new thrombosis and death due to thrombosis, in patients with heparin-induced thrombocytopenia.

Danaparoid for heparin-induced thrombocytopenia: an analysis of treatment failures

BACKGROUND

Patients with heparin-induced thrombocytopenia (HIT) (with or without thrombosis) require alternative anticoagulation because of their extreme risk of new thromboembolic complications. The first effective agent for this purpose may be danaparoid, a less-sulfated low molecular weight heparinoid. Recently, direct thrombin inhibitors have been used.

OBJECTIVE

Five HIT patients, who developed new thromboembolic complications while receiving danaparoid, were analyzed to consider possible reasons for treatment failure and to promulgate strategies that improve efficacy.

RESULTS

Three patients had acute HIT, one had recent HIT, and one with remote HIT was re-exposed to heparin during heart surgery. Danaparoid was started as intravenous bolus and infusion in one patient, and as 1250 units subcutaneously twice daily in four patients. The new complications that emerged on danaparoid were new venous thrombi in three patients (one with pulmonary emboli), lower extremity arterial thrombosis in one, myocardial ischemia in one, thromboembolic cardiovascular accidents in one, and fatal bowel necrosis in one (two patients suffered more than one complication). Platelet counts did not improve or worsened in four, improved partially in the other, and parameters of disseminated intravascular coagulation failed to improve in one patient. Four patients responded relatively dramatically when direct thrombin inhibitors were substituted. Possible reasons for danaparoid failure include that: 1) no treatment is expected to completely prevent complications, 2) antithrombin III consumption can blunt efficacy in some patients, 3) low or intermediate doses may be insufficient, and 4) there was clinically significant cross-reactivity of the pathogenic HIT antibodies.

CONCLUSIONS

It is emphasized that the possibility of clinically significant antibody cross-reactivity and that low or intermediate dosage may be inadequate when using danaparoid in therapy of HIT. The latter problem probably extrapolates to other anticoagulants used for HIT.

Comparison of thrombopoiesis during ITP and HIV-ITP and response to intravenous gammaglobulin treatment

Immune thrombocytopenic purpura's diagnosis (ITP) is based on low platelet count and exclusion of clinical conditions rather than a specific diagnostic test. We used the reticulated platelet (RP) assay to study ITP and thrombocytopenia associated with HIV infection (HIV-ITP). Data from 96 ITP and 23 HIV-ITP patients showed low platelet counts (PC) with both high or low %RP suggesting that individuals have different degrees of thrombopoiesis. About 20% of ITP and 46% of HIV-ITP patients had %RP in the 'low' or 'normal' ranges. Grouped by platelet count <30x10(9)/L, 24% ITP and 36% HIV-ITP patients had 'low' to 'normal' %RP. The patient population did not show correlation between PC and %RP, but individuals showed an inverse relationship. Within a week of receiving IVIG, 18 ITP and 9 HIV-ITP patients' PC increased, %RP decreased. Patients with %RP measured within 24 h of IVIG treatment had lower %RP than expected, suggesting dilution by an older platelet population. ITP and HIV-ITP patients' responses to i.v. gammaglobulins were similar. Thrombopoietin levels of ITP patients did not correlate with PC, %RP, or RP count. Estimation of thrombopoiesis by RP assay provides useful information for differentiation among thrombocytopenias.

Regression of intracardiac heparin-induced thrombosis after aortic root surgery

Heparin-induced thrombocytopenia and thrombosis syndrome (type II) is associated with thromboembolic complications and a mortality rate up to 30%. We describe a patient who developed intracardiac and aortic Dacron prosthesis heparin-induced thrombosis after aortic root conservative surgery. Successive transoesophageal echocardiographies demonstrated a progressive regression of intracardiac thrombosis with oral anticoagulation by warfarin and antiplatelet therapy combining aspirin and clopidogrel.

Periostitis secondary to interleukin-11 (Oprelvekin, Neumega). Treatment for thrombocytopenia in pediatric patients

Interleukin-11 (Oprelvekin, Neumega) is a newly introduced thrombopoietic growth factor that stimulates production, differentiation, and maturation of megakaryocytes and platelets. Reversible periostitis has been reported as the side effect of the drug in primates and in the phase I/II trials. We report our experience with 5 cases of periostitis, occurring in thrombocytopenic children with three non-malignant and two malignant conditions, out of 24 pediatric patients treated with IL-11 at 75 micro g/kg per day for a median of 17 days. The findings were noted in the clavicle or the proximal humerus. Two patients also had forearm and lower-extremity long-bone involvement. All patients had normal bones before IL-11 was given, changes occurred in both non-malignant and malignant diseases, and periostitis disappeared after use of the drug was discontinued. The distribution and appearance of the changes are similar to prostaglandin E1 and hypervitaminosis A. The changes are reversible after termination of treatment and are most noted in younger patients. The exact mechanism is not clear. The detection of periostitis makes it essential for the radiologists to inquire as to what medications patients are receiving. The pediatric doses (75 g/kg/d) are above those recommended for adult patients (50 g/kg/d) and this may account for the pediatric bone changes of periostitis.

Argatroban dosing in patients with heparin-induced thrombocytopenia

OBJECTIVE

To retrospectively evaluate clinical experiences with argatroban dosing, particularly incremental dosage adjustments, during a clinical trial of argatroban anticoagulation in heparin-induced thrombocytopenia (HIT).

METHODS

Records of 304 patients with HIT administered argatroban during a prospective study were reviewed to determine each dose, incremental dosage adjustment, and duration of therapy. Dosing information (stratified by patient initial dose) and incremental adjustments (overall, and stratified by dose from which adjustment occurred) were summarized. The relationship between median incremental adjustments and adverse outcomes, including bleeding, was investigated.

RESULTS

Two hundred seventy-one (89%) patients received initial doses of 1.9-2.1 micro g/kg/min (group B). Twenty-six (9%) patients were started at a lower dose. Group B's median (5-95th percentile) final dose was 1.6 (0.25-4.0) micro g/kg/min. During a median of 6 days of argatroban therapy, patients underwent a median of 3.0 dosage adjustments using a median and mode incremental adjustment of 0.5 micro g/kg/min (5-95th percentile, 0.1-2.0 micro g/kg/min). Fifty-two (17%) patients required no dosage adjustment. Incremental adjustments decreased with decreasing current dose (e.g., median 0.25 micro g/kg/min from doses of 0.26-0.75 micro g/kg/min). Outcomes were similar between patients with no adjustment or with median incremental adjustments of </=0.4, 0.41-0.75, or >0.75 micro g/kg/min.

CONCLUSIONS

Based on this clinical experience, together with the established linear pharmacokinetics and pharmacodynamics of argatroban, appropriate dosage increments may be proposed for argatroban-treated patients with HIT. Incremental adjustments of 0.5 micro g/kg/min are reasonable for most patients. Smaller adjustments (e.g., 0.25 micro g/kg/min) should be used when modifying lower doses, such as those recommended for use in hepatically impaired patients.

Increased local procoagulant action: a mechanism contributing to the favorable hemostatic effect of recombinant FVIIa in PLT disorders

BACKGROUND

Recombinant FVIIa (rFVIIa) has been shown to improve hemostasis in patients with thrombocytopenia and to prevent or control bleeding episodes in patients with inherited deficiencies of major PLT glycoproteins, but the mechanism of action is not well understood.

STUDY DESIGN AND METHODS

Effects of rFVIIa on hemostasis were explored with an in vitro perfusion technique. Blood samples, from healthy donors or from patients with congenital defects of PLT glycoprotein IIb-IIIa (GPIIb-IIIa), were anticoagulated with low-molecular-weight heparin. Experimental thrombocytopenia (<6000 PLTs/microL) was induced by a filtration procedure. rFVIIa was added to blood samples at therapeutic concentrations. A severe GPIIb-IIIa impairment was also induced by exposure of normal blood samples to a specific antibody. Perfusion studies were performed through annular chambers containing damaged vascular segments. The presence of fibrin and PLTs on the perfused subendothelium was morphometrically quantified.

RESULTS

Under conditions of experimental thrombocytopenia, addition of rFVIIa enhanced fibrin formation in a dose-dependent manner (p < 0.05). Improvements in local fibrin generation and partial restoration of PLT interactions were also observed after incubation of blood from patients with Glanzmann's thrombasthenia with rFVIIa at 5 microg per mL (180 microg/kg). Similar improvements were observed in blood samples incubated with antibodies to GPIIb-IIIa. rFVIIa in whole normal blood also enhanced fibrin formation but PLT deposition was unaffected. Evaluation of prothrombin fragments 1 and 2 in the perfusates confirmed that rFVIIa increased thrombin generation in all cases.

CONCLUSION

Our data indicate that rFVIIa promotes a procoagulant activity at sites of vascular damage. This mechanism could explain the beneficial hemostatic effect of rFVIIa in patients with thrombocytopenia or with Glanzmann's thrombasthenia.