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Biomedical subjects

Sam Schulman

Publications and source records attributed to Sam Schulman.

33 records · Page 2Linked to original sources
PubMed2003

Secondary prevention of venous thromboembolism with the oral direct thrombin inhibitor ximelagatran.

BACKGROUND: For many patients with venous thromboembolism, secondary prevention with vitamin K antagonists is not extended beyond six months, since the risk of recurrence may be outweighed by the risk of major bleeding. METHODS: In a double-blind, multicenter trial, we randomly assigned 1233 patients with venous thromboembolism who had undergone six months of anticoagulant therapy to extended secondary prevention with the oral direct thrombin inhibitor ximelagatran (24 mg) or placebo, taken twice daily, for 18 months without monitoring of coagulation. At base line, bilateral ultrasonography of the legs and perfusion lung scanning were performed. RESULTS: Data from 612 patients in the ximelagatran group and 611 in the placebo group were analyzed. The occurrence of the primary end point, symptomatic recurrent venous thromboembolism, was confirmed in 12 patients assigned to ximelagatran and 71 patients assigned to placebo (hazard ratio, 0.16; 95 percent confidence interval, 0.09 to 0.30; P<0.001). Death from any cause occurred in 6 patients in the ximelagatran group and 7 patients in the placebo group, and bleeding occurred in 134 patients and 111 patients, respectively (hazard ratio, 1.19; 95 percent confidence interval, 0.93 to 1.53; P=0.17). The incidence of major hemorrhage was low (six events in the ximelagatran group and five in the placebo group), and none of these hemorrhages were fatal. The cumulative risk of a transient elevation of the alanine aminotransferase level to more than three times the upper limit of normal was 6.4 percent in the ximelagatran group, as compared with 1.2 percent in the placebo group (P<0.001). CONCLUSIONS: Oral ximelagatran was superior to placebo for the extended prevention of venous thromboembolism. There was no significant increase in the frequency of bleeding complications, but there was an increase in the number of patients with a transient elevation in the alanine aminotransferase level.

Administration, Oral↗
PubMed2003

Limited protective effect of the CCR5Delta32/CCR5Delta32 genotype on human immunodeficiency virus infection incidence in a cohort of patients with hemophilia and selection for genotypic X4 virus.

The relationship among CCR5 genotype, cytomegalovirus infection, and disease progression and death was studied among 159 human immunodeficiency virus (HIV)-infected patients with hemophilia. One patient (0.6%) had the CCR5Delta32/CCR5Delta32 genotype (which occurs in approximately 2% of the Scandinavian population) and a rapid disease course. His HIV V3 region contained genotypic features attributable to X4 virus and resembled functionally verified X4 virus and virus from patients treated with a CD4 cell-stimulating drug, tucaresol. Age-related differences in disease progression rate and survival time were seen for CCR5/CCR5 patients. Surprisingly, no protective effect of the CCR5/CCR5Delta32 genotype on disease progression or survival was seen for children but was evident for adults. Age group-related immunologic differences might explain this variation, and transmission route and/or viral phenotype variation within donor virus may be related to the limited protection of the CCR5Delta32/CCR5Delta32 genotype. Sequence comparisons indicate that X4 virus can be selected in vivo due to either absence of CCR5 receptors or relative increase of CXCR4 receptors.

Adolescent↗
PubMed2003

Why is factor Xa not a better target than factor IIa for therapeutic inhibition of coagulation?

The rapid development of new and selective anticoagulant agents has triggered the question of which activated coagulation factor would be a better target for the inhibition of coagulation. Indirect comparisons between studies on the different drugs are problematic due to the plethora of characteristics that may differ between them. Even head-to-head comparisons in the same study may not determine the optimal target due to differences in pharmacokinetics between the agents. Therefore, the answer to this question relies on theoretical speculations based on knowledge of some of the factors that seem to have an influence on efficacy and safety. Ultimately, drugs with equal pharmacokinetic characteristics that are administered in equipotent doses may have a similar global effect on coagulation, independent of the inhibitory mechanism. Conversely, the differentiated inhibition of the coagulation protease on vascular receptors may play a greater role for effects that are not traditionally considered as part of hemostasis.

Anticoagulants↗
PubMed2003

Acquired hemophilia masked by warfarin therapy: report on two cases.

Spontaneous appearance of acquired anticoagulants is a rare phenomenon. We present two cases, where such antibodies against factor VIII were masked by warfarin therapy. The two patients were anticoagulated with warfarin due to mechanical heart valve and recurrent thromboembolic events, respectively. Different therapies against the inhibitor of factor VIII were used in the two cases. One patient received corticosteroids and high-dose gammaglobulin with temporary effect and was then effectively treated with cyclophosphamide. The other patient was successfully treated with cyclosporine. The special problems of keeping the balance between thrombosis and bleeding in this group of patients with need of anticoagulation due to mechanical heart valves or other thrombogenic factors are discussed.

Autoantibodies↗
PubMed2003

Platelet-leukocyte aggregation under shear stress: differential involvement of selectins and integrins.

Platelets and leukocytes can form heterotypic aggregates. We studied how shear stress influences platelet-leukocyte aggregation (PLA). Shear stress was applied to hirudinized blood, using a cone-and-plate(let) analyzer. Platelet and leukocyte activation and PLA formation were monitored by flow cytometry. Shear stress per se increased platelet P-selectin expression, leukocyte CD11b expression, and PLA formation. Shear-induced heterotypic aggregation was seen among monocytes and neutrophils, but not lymphocytes. ADP induced marked PLA formation, but this was reduced by shear stress. fMLP mildly increased PLA formation, and this effect was enhanced by shear stress. P-selectin blockade abolished, whilst GPIIb/IIIa blockade enhanced shear- and agonist-induced PLA formation. At 1800 s(-1), shear-and agonist-induced PLA formation were maintained or further enhanced with GPIIb/IIIa blockade alone, but reduced by simultaneous blockade of GPIIb/IIIa, CD11b, and CD18. In conclusion, shear stress per se enhances PLA formation. With agonist stimulation, shear stress enhances PLA formation primarily mediated by integrins, but attenuates PLA formation primarily mediated by P-selectin. The present results indicate that P-selectin-mediated bridging is essential for the initiation of PLA formation, while integrin-bridgings contribute importantly to the stability of heterotypic conjugates under high shear stress.

Adult↗
PubMed2003

Helicobacter pylori causes gastrointestinal hemorrhage in patients with congenital bleeding disorders.

Helicobacter pylori (H. pylori) infection is associated with peptic ulcer disease and gastric cancer. The eradication of H. pylori is of special interest in patients with congenital bleeding disorders, for whom treatment of gastrointestinal hemorrhage with factor concentrates is costly. The prevalence of H. pylori varies between different populations and identification of high-risk subgroups may allow for more targeted screening and eradication of the infection. We performed a 5-year retrospective study of gastrointestinal bleeding, combined with screening and treatment for H. pylori and a long-term prospective follow-up in 168 Swedish and 23 Estonian patients with hemophilia or von Willebrand disease. The prevalence of seropositivity was lower in Sweden than in Estonia (28 versus 48%, p = 0.03), lower in native Swedes than in non-Nordic immigrants to Sweden (20 versus 76%, p = 0.0001) and lower in patients less than 40 years of age than older patients (16 versus 38%, p = 0.002). The incidence of gastrointestinal hemorrhages among the 35 Swedish patients with active H. pylori infection, confirmed by a urea breath test, was 6.0 per 100 patient-years before eradication therapy versus 1.7 during the prospective followup. A negative urea breath test one month after therapy always remained negative after one year. Screening, followed by treatment of all infected patients, yielded a reduction of direct costs over a 5-year period of 130 US-$ per screened patient. We conclude that screening and eradication therapy for infection with H. pylori in patients with congenital bleeding disorders is an effective and economic strategy.

Adolescent↗
PubMed2002

Hypofibrinolytic state in HIV-1-infected patients treated with protease inhibitor-containing highly active antiretroviral therapy.

Decreased insulin sensitivity, hyperlipidemia, and body fat changes are considered as risk factors for coronary heart disease (CHD). A clustering of such factors (metabolic syndrome [MSDR]) exponentially increases the risk. Impaired fibrinolysis and increased coagulation are additional independent risk factors for CHD. We studied the effects of protease inhibitor (PI)-containing highly active antiretroviral therapy (HAART) on metabolic and hemostatic parameters in 363 HIV-infected individuals, of whom 266 were receiving PI-containing HAART and 97 were treatment naive. The fasting plasma levels of insulin, glucose, triglycerides, cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, plasminogen activator inhibitor type 1 (PAI-1), and fibrinogen were evaluated together with the areas of visceral adipose tissue and the visceral adipose tissue/subcutaneous adipose tissue area ratio. The levels of insulin, triglycerides, cholesterol, and low-density lipoprotein cholesterol; visceral adipose tissue area; low-density lipoprotein/high-density lipoprotein ratio; and visceral adipose tissue/subcutaneous adipose tissue area ratio were significantly increased in patients receiving PI-containing HAART compared with treatment-naive patients. The levels of PAI-1 and fibrinogen were significantly higher in patients receiving PI-containing HAART. PAI-1 levels were higher in individuals with MSDR but also in patients without MSDR who were receiving PI-containing HAART. PAI-1 was independently correlated to use of PI-containing HAART, triglyceride level, insulin level, and body mass index (p <.001). These findings suggest that patients receiving PI-containing HAART have decreased fibrinolysis and increased coagulability, which may thus represent additional risk factors for cardiovascular disease in this patient group.

Adipose Tissue↗
PubMed2002

Experiences of a low-intensity anticoagulation regimen for extended secondary prevention of venous thromboembolism.

Extended treatment with vitamin K antagonists for more than 6 months is often used for secondary prevention of venous thromboembolism (VTE) in patients at high or moderate risk for recurrent events. The intensity of anticoagulant therapy is usually maintained at an International Normalized Ratio (INR) of 2-3. An INR of 1.5-2 might also prevent thromboembolic events with less complications of bleeding, but results from randomized trials are not yet available. In a non-prospective, uncontrolled study 40 patients with a history of VTE and an estimated high risk for recurrent events due to several previous events and/or thrombophilic defects were, after a median of 11.5 months on regular intensity anticoagulation (INR 2-3), switched to a low intensity regimen (INR 1.5-2). In six of the patients an estimated high risk for complications of bleeding contributed to this decision. After a median follow-up of 36 months (140 patient-years) recurrent events, complications of bleeding and some basic quality of life measurements regarding the new treatment were registered. No recurrent events, four minor bleedings and no major bleedings were registered. Twenty-six patients preferred an INR of 1.5-2 compared to 2-3. The main reasons for that preference were a lower risk for bleeding (13 patients) and less frequent monitoring of the INR (18 patients). No patient preferred full-dose anticoagulation at INR 2-3. In patients at a high risk for recurrence of VTE an initial period of regular intensity anticoagulation, followed by a low-intensity regimen, may provide effective and safe secondary prophylaxis.

Adult↗
PubMed2002

Inhibition of warfarin activity by ribavirin.

OBJECTIVE: To report a case of inhibition of the effect of warfarin during treatment with ribavirin. CASE SUMMARY: A 61-year-old white man received combination treatment with interferon and ribavirin during 1 year for chronic hepatitis C. He was on permanent anticoagulant therapy with warfarin after a previous heart valve replacement. The dose of warfarin had to be increased by approximately 40% to maintain the desired level of anticoagulation. DISCUSSION: Interferon has previously been reported to potentiate the effect of warfarin. This is the first case published in the English-language literature describing an inhibition of the effect of warfarin by the combination of interferon and ribavirin. A rechallenge with ribavirin demonstrated that the inhibition of warfarin could be reproduced. The mechanism for this interaction is unclear. The pharmacokinetics of ribavirin and the potential pathways for interaction are discussed. CONCLUSIONS: During 4 weeks after starting or discontinuing treatment with ribavirin, prothrombin time may be affected in patients receiving warfarin for anticoagulation. It seems prudent to monitor warfarin therapy more frequently during those periods.

Anticoagulants↗