Lepirudin use in a neonate with heparin-induced thrombocytopenia

OBJECTIVE

To describe a case of heparin-induced thrombocytopenia (HIT) in a premature infant and the doses of danaparoid and lepirudin needed to achieve appropriate therapeutic endpoints.

CASE SUMMARY

A 30-week gestational age infant was diagnosed with HIT with heparin antibodies. Danaparoid 2.0-2.4 units/kg/h achieved anti-Xa levels of 0.2-0.4 U/mL, but thrombocytopenia failed to resolve. Lepirudin was started in place of danaparoid. Lepirudin doses of 0.03-0.05 mg/kg/h achieved target activated partial thromboplastin time values of 1.5-2.0 times baseline.

DISCUSSION

Dosing information for danaparoid in neonates is limited, and information for lepirudin appears only in German literature at this time. HIT is well documented in newborns, and lepirudin use in these situations is likely to increase. This report provides some guidance for optimal dosing. It also provides some guidance for HIT evaluation in preterm infants, in whom blood volume for laboratory tests is a major issue.

CONCLUSIONS

HIT is an important and potentially fatal problem in neonates. Lepirudin may be the drug of choice, especially since danaparoid is now unavailable. Initial lepirudin dosing should not exceed 0.05 mg/kg/h.

Therapeutic uses of MAbs directed against CD20

BACKGROUND

There are two main classes of Abs directed against the CD20 Ag that have been developed for therapeutic intent: unconjugated and radio-labeled Abs.

METHODS

The clinical results available from the large clinical trials utilizing both the unconjugated and radiolabelled Abs are summarized in this article.

DISCUSSION

Both of these classes of agents have shown promise in clinical trials both alone and in conjunction with conventional chemotherapy or high-dose chemotherapy and transplantation. Ongoing research with these agents will provide further evidence of the place in clinical practice for these agents.

Combination platelet glycoprotein IIb/IIIa receptor and lepirudin administration during percutaneous coronary intervention in patients with heparin-induced thrombocytopenia

We evaluated a combination therapy using glycoprotein IIb/IIIa receptor antagonism and direct thrombin inhibition in nine patients with heparin-induced thrombocytopenia (HIT) undergoing 10 percutaneous coronary interventions (PCIs). In selected patients with HIT, the combination of a direct thrombin inhibitor, lepirudin, and abciximab, tirofiban, or eptifibatide appears to be a safe and effective anticoagulation strategy for PCI.

Thrombocytopenia in patients with HCV-positive chronic hepatitis: efficacy of leucocyte interferon-alpha treatment

Treating patients with HCV-associated thrombocytopenia is a problem, because the pathogenesis of thrombocytopenia is still unclear. We evaluated the clinical and haematological response to leucocyte interferon-alpha in 20 naive patients with chronic hepatitis C and thrombocytopenia (platelet count <140 x 10(9)/l for at least six months) without portal hypertension and/or hypersplenism. They were treated with leucocyte interferon-alpha (3 MU three times per week) for 12 months and followed up for 12 months. Biochemical (ALT) and virological (HCV-RNA) responses were determined. Two patients discontinued treatment because of hyperthyroidism. Of the 18 patients who completed treatment, 12 (66%) showed a biochemical response, 10 of whom (55.5%) also showed a virological response. At the end of follow-up, four patients (22%) showed a complete (biochemical and virological) response. During treatment, platelet counts decreased to less than 10-20% of pretreatment values in most patients. Three of the four patients with a complete response showed a platelet increase during treatment and throughout the follow-up period. In HCV-associated thrombocytopenia leucocyte interferon-alpha is well tolerated and in cases of sustained virological inhibition is able to ameliorate the disease by increasing the platelet count.

Catastrophic antiphospholipid-antibody syndrome and danazol

We report a case of catastrophic antiphospholipid-antibody syndrome, with renal and neurological manifestations, which presented shortly after the institution of danazol for the treatment of refractory thrombocytopenia.

Pharmacokinetic and pharmacological interactions between ticlopidine hydrochloride andKangen-Karyu - Chinese traditional herbal medicine

Kangen-Karyu (KGK), containing peony root, cnidium rhizome, saf flower, cyperus rhizome, saussurea root and Salvia miltiorrhiza root, is a Chinese traditional medicine formula to invigorate the 'blood' and dispel 'blood stasis', arising from poor blood circulation. The present study evaluated the pharmacokinetic and pharmacological interactions between KGK and ticlopidine hydrochloride. Ticlopidine was administered orally or intravenously to KGK-treated rats, and its plasma concentrations were measured. KGK did not significantly affect the pharmacokinetic parameters of ticlopidine in rats treated with both oral and intravenous administration. Ticlopidine alone significantly prolonged the mouse tail-bleeding time and adenosine 5'-diphosphate-induced ex vivo platelet aggregation, which was slightly augmented by KGK. It is suggested that the combined therapy of ticlopidine and KGK may augment the antithrombotic effects, and that the dosage of ticlopidine should be reduced to prevent thrombotic thrombocytopenic purpura, a severe adverse effect of ticlopidine.

Recombinant activated factor VII: its mechanism of action and role in the control of hemorrhage

PURPOSE

Recombinant activated factor VII (rFVIIa) has proven both safe and efficacious in the treatment of bleeding episodes in patients with hemophilia A or B who have developed inhibitors. More recently, a growing number of reports suggests that rFVIIa may also have indications for the treatment of bleeding in patients with other hemostatic disorders, including qualitative and quantitative platelet defects, factor deficiencies other than hemophilia, and in otherwise healthy patients with uncontrollable hemorrhage following surgery or trauma. We have attempted to reconcile the various proposed mechanisms of action of rFVIIa with its apparent efficacy in such diverse clinical settings.

SOURCE

A review of the literature was performed to determine those clinical scenarios in which rFVIIa appears to have been effective in controlling associated hemorrhage.

PRINCIPAL FINDINGS

Findings from our group and others have demonstrated that rFVIIa is able to directly activate factor X and increase thrombin production on the surface of activated platelets in the absence of factor VIII or IX, as well as to improve thrombin generation in thrombocytopenia, and to yield a fibrin dot more resistant to fibrinolysis in vitro.

CONCLUSIONS

Through these primary mechanisms, we believe that rFVIIa may be able to compensate for a variety of defects in hemostasis and merits further investigation as a general therapeutic for uncontrollable hemorrhage.

[Treatment with lepirudin in heparin-induced thrombocytopenia. A case report]

We report the case of a 71 old woman presenting a bilateral massive pulmonary embolism with intraventricular right thrombus complicating heparin induced thrombocytopenia (HIT) persistent after one month of conventional anticoagulant processing. We underline the effectiveness of lepirudin (Refludan) in the curative processing of pulmonary embolism allowing here to avoid a complex surgical thromboembolectomy. We evoke the place of this molecule in the curative therapeutic strategy of HIT with thrombotic phenomena.

Clonal T cell-mediated cyclic thrombocytopenia

Cyclic thrombocytopenia is a rare disorder characterized by periodic platelet count fluctuations of unknown aetiology. We report on a female patient with cyclic changes of platelet counts ranging from 6 x 10(9)/l to 753 x 10(9)/l in 4-week intervals. Platelet counts were inversely correlated to thrombopoietin levels suggesting production failure. Reticulocyte counts and neutrophil counts showed similar, but less prominent, fluctuations. Clonal T-cell receptor rearrangement was detected in bone marrow samples as well as in peripheral blood. Cell typing of blood lymphocytes revealed a relative increase in CD3+ T cells. Treatment with cyclosporine A resulted in a substantial improvement of platelet counts. Taken together, we provide evidence for clonal T-cell mediated bone marrow failure with cyclic impairment of thrombopoiesis responsive to cyclosporine therapy.

Recombinant human thrombopoietin: basic biology and evaluation of clinical studies

Thrombocytopenia is a common medical problem for which the main treatment is platelet transfusion. Given the increasing use of platelets and the declining donor population, identification of a safe and effective platelet growth factor could improve the management of thrombocytopenia. Thrombopoietin (TPO), the c-Mpl ligand, is the primary physiologic regulator of megakaryocyte and platelet development. Since the purification of TPO in 1994, 2 recombinant forms of the c-Mpl ligand--recombinant human thrombopoietin (rhTPO) and pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF)--have undergone extensive clinical investigation. Both have been shown to be potent stimulators of megakaryocyte growth and platelet production and are biologically active in reducing the thrombocytopenia of nonmyeloablative chemotherapy. However, neither TPO has demonstrated benefit in stem cell transplantation or leukemia chemotherapy. Other clinical studies have investigated the use of TPO in treating chronic nonchemotherapy-induced thrombocytopenia associated with myelodysplastic syndromes, idiopathic thrombocytopenic purpura, thrombocytopenia due to human immunodeficiency virus, and liver disease. Based solely on animal studies, TPO may be effective in reducing surgical thrombocytopenia and bleeding, ex vivo expansion of pluripotent stem cells, and as a radioprotectant. Ongoing and future studies will help define the clinical role of recombinant TPO and TPO mimetics in the treatment of chemotherapy- and nonchemotherapy-induced thrombocytopenia.

Challenges in the development of platelet growth factors: low expectations for low counts

Thrombocytopenia remains a significant clinical problem for which only symptomatic therapy, namely platelet transfusion, is available for management of acute events. Platelet transfusions are often complicated by febrile reactions, as well as the risk of transmission of infectious agents and the likelihood of alloimmunization, which then decreases the effectiveness of additional transfusion support. The availability of a hematopoietic cytokine that could reliably stimulate platelet recovery, analogous to the effect of granulocyte colony-stimulating factor on neutrophil recovery following chemotherapy, would greatly enhance supportive care in cancer and provide an effective therapy for a variety of diseases that cause thrombocytopenia. To identify such a thrombopoietic cytokine, studies initially focused on regulatory molecules that stimulates early multipotent hematopoietic progenitors, such as interleukin-1 and interleukin-6. Unfortunately, these cytokines had poor efficacy and significant toxicity in human testing. Recombinant human interleukin-11, an early-acting cytokine, has modest efficacy and clinically challenging toxicities, but in the absence of other active drugs, it has been licensed for prevention of severe chemotherapy-induced thrombocytopenia. Recent interest has focused on analogs of thrombopoietin, the endogenous regulator of thrombopoiesis, which have the potential for much greater efficacy with minimal toxicity due to the more specific targeting of megakaryocyte-specific signaling.

[Heparin-induced thrombocytopenia syndrome and thrombosis in patients undergoing periodic haemodialysis]

Heparin-induced thrombocytopenia (HIT) is the most important immunological drug reaction that patients face today. Being unfractionated heparin the standard anticoagulation used in haemodialysis, acute or chronic uremic patients starting haemodialysis are at risk of developing HIT. Through the accurate description of two patients, one with chronic and the other with acute uraemia, who developed this complication at the start of haemodialysis, we compare the distinct clinical problems of haemodialysis-related HIT with the general clinical features of HIT. We report the occurrence of repeated clotting of both dialysers and catheters, as well as thrombosis of the central veins where the catheters are placed and of the fistulas. We also report an accurate review of the literature on haemodialysis-related HIT. We have observed that HIT seems to be particularly rare in haemodialysis patients. Since newly treated haemodialysis patients are at risk of developing HIT, and most of the studies were made on long-term chronic haemodialysis patients, we assume that the syndrome is poorly documented. Our own experience on 37 haemodialysis patients who developed HIT is reported by focusing on both the clinical presentation of HIT as well as the long-term follow up of the patients. We present some considerations on the treatment options of acute HIT in uremic patients as well as on the problem of heparin re-exposure subsequent to the HIT episode, a very prominent problem in chronic haemodialysis patient.

Danazol for the treatment of thrombocytopenia in patients with myelodysplastic syndrome

Thrombocytopenia is a poor prognostic indicator in the myelodysplastic syndromes (MDS). Treatment options for patients with symptomatic thrombocytopenia are limited. Danazol, an attenuated androgen, may have some efficacy in increasing the platelet count of patients with MDS. We retrospectively reviewed 33 patients with primary MDS who were treated with danazol for 6 or more weeks. After 6 weeks on danazol, the mean platelet count increased from 42 x 10(9)/L to 60 x 10(9)/L (P < 0.015), and 25 out of 33 patients (76%) had an increase in their platelet counts. Following 12 weeks of treatment, the mean platelet count increased to 67 x 10(9)/L (P < 0.005), and 21 out of 29 patients (72%) had an increase in their platelet counts. Seven out of nine patients no longer required platelet transfusions because bleeding stopped after 6 weeks on danazol. Mean duration of response was 10 months (range 2-68 months). Responses were seen in all French-American-British (FAB) subtypes and in all International Prognostic Scoring System (IPSS) scores. Therapy was well tolerated. Danazol may be effective in MDS patients who are thrombocytopenic.

Hematopoietic abnormalities in mice deficient in gp130-mediated STAT signaling

OBJECTIVE

Studies on mice lacking the common receptor subunit gp130 reveal that activation of gp130-dependent signaling pathways is essential for normal fetal and adult hematopoiesis. However, the extent to which hematopoiesis is dependent upon activation of a particular gp130 signaling pathway, namely STAT1/3 or SHP2/MAPK, is unknown. This study examined the specific contribution of gp130-mediated STAT1/3 signaling to the regulation of hematopoiesis.

MATERIALS AND METHODS

Hematopoiesis was examined at various developmental stages in mice homozygous for a targeted carboxy-terminal truncation mutation in gp130 (gp130(delta)/(delta)) that deletes all STAT1/3 binding sites, thereby abolishing gp130-mediated STAT1/3 activation.

RESULTS

Adult gp130(delta)/(delta) mice have increased numbers of immature colony-forming unit spleen progenitor cells in the bone marrow and spleen, elevated numbers of committed myeloid progenitor cells in the spleen and peripheral blood, and leukocytosis. Increased progenitor cell production was observed in gp130(delta)/(delta) fetal livers from 14 days of gestation onward. In contrast, the circulating platelet count was reduced by 30% in gp130(delta)/(delta) mice, without any corresponding decrease in the number of bone marrow and splenic megakaryocytes. In liquid cultures, megakaryocytes from gp130(delta)/(delta) mice are smaller than those from wild-type mice and do not increase in size upon stimulation with interleukin-6 or interleukin-11. Administration of either interleukin-6 or interleukin-11 to gp130(delta)/(delta) mice failed to increase platelet numbers, despite an increase in the production of megakaryocytes.

CONCLUSIONS

Collectively, these results reveal that gp130-mediated STAT1/3 activation is required to maintain the normal balance of hematopoietic progenitors during fetal and adult hematopoiesis. Furthermore, they suggest two distinct roles for gp130-mediated STAT1/3 activation in hematopoiesis, one restricting the production of immature hematopoietic progenitor cells and the other promoting the functional maturation of megakaryocytes to produce platelets.

Treatment of myelodysplastic syndromes with 5-azacytidine

Patients with myelodysplastic syndromes (MDS) who were anemic and/or thrombocytopenic were treated with 5-azacytidine (5-AZA) at a dose of 75 mg/m(2) per day SQ x 7 days. This cycle was repeated every 28 days. Forty-eight patients who received at least one cycle of 5-AZA were evaluable for response. Hematological toxicity was mild and consisted of thrombocytopenia and leukopenia. Extramedullary toxicity was uncommon and consisted of pneumonia, arthralgia, diarrhea, and injection site irritation. Eighteen of the 46 transfusion dependent patients became transfusion independent (39%). Median duration of response was 7 months with three patients continuing beyond 2 years. French Anglo British (FAB) classification and the International Scoring System (ISS) did not predict response to 5-AZA. However, a decrease in the white blood cells (WBC) during the initial cycle of 5-AZA correlated with a higher response rate.

Heparin-induced thrombocytopenia-alternative anticoagulation in pregnancy and lactation

Heparin-induced thrombocytopenia (HIT) appears rarely in pregnant patients who are being treated with heparin. When HIT is suspected, heparin treatment should be discontinued and alternative anticoagulation should be started. The heparinoid danaparoid appears to be the drug of choice for acute treatment and prophylaxis because of its low placental permeability. Between the 12th and 36th weeks of pregnancy, either danaparoid may be continued or warfarin may be used after recovery of platelet counts. Before and during delivery, danaparoid should be preferred over warfarin in order to avoid bleeding complications in mother and infant. Hirudin should only be used when either cross-reactivity with heparin-induced antibodies or cutaneous allergy against heparinoids are observed. Postpartum warfarin seems to be the treatment of choice because breast-feeding can be continued. Alternative treatment with either danaparoid or hirudin is possible, but data on treatment with these reagents in lactating mothers are very limited.

Hirudin in heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT), a serious side effect of heparin treatment, requires alternative anticoagulation in most affected patients. The recombinant hirudin (r-hirudin) lepirudin has been approved for this purpose after two prospective trials in laboratory-confirmed HIT patients. Other drugs available for this purpose are danaparoid sodium (a heparinoid) and argatroban, a synthetic direct thrombin inhibitor. In this article, recommendations for optimal use of r-hirudin in HIT are given, covering therapy in uncomplicated patients as well as in special situations such as heparin reexposure of HIT patients. Because lepirudin's half-life depends on renal function, it may vary between 1 and 200 hours, which requires individual dose adjustments. Lepirudin compares favorably with danaparoid, based on retrospective data. No direct comparisons of lepirudin with argatroban are available, but argatroban might offer advantages in patients with renal failure, because it is mainly eliminated hepatically. Major hemorrhage, the main risk of lepirudin treatment, occurring in about 15% of patients, makes close monitoring important. New monitoring tools, such as the ecarin clotting time (ECT), might further reduce bleeding risks. Antihirudin antibodies, which can alter the pharmacokinetics as well as the pharmacodynamics of hirudin, can also be countered by close monitoring and appropriate dose adjustments. Whereas hirudins have not yet managed to gain importance in non-HIT indications such as unstable coronary syndromes, they have a major role to play in the treatment of HIT. The choice between the available drugs for HIT, namely lepirudin, danaparoid, and argatroban, has to be made according to the clinical presentation of the patient.

Hirudin in acute coronary syndromes

Acute coronary syndromes are a major cause of morbidity and mortality in Western societies. The term describes a spectrum from unstable angina, the recently defined non-Q wave infarction (the Non ST-Elevation Myocardial Infarction [NSTEMI]), to acute transmural myocardial infarction. With regard to treatment, a series of recently published studies compared the specific direct thrombin inhibitor hirudin with standard unfractionated heparin. Initial small studies showed promising results and led to the initiation of large-scale clinical trials addressing patients with acute coronary syndromes. However, in these studies, an unacceptably high incidence of serious hemorrhagic complications prompted safety boards to stop trials. In those studies carried out according to the protocol, no significant clinical benefit of hirudin over standard heparin was proved. Here, hirudin has been shown to be equivalent to unfractionated heparin for the treatment of unstable coronary syndromes with or without ST elevation and as an adjunct to percutaneous coronary balloon angioplasty. Because of its narrow therapeutic window between clinical benefit and increased bleeding hazards, hirudin should be used cautiously. For patients with heparin-induced thrombocytopenia, hirudin is accepted as an important therapeutic alternative.