Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027947 (neutropenia)
 17,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Clopidogrel is a new thieno-pyridine derivative and has a more potent inhibitory effect on platelet aggregation, dependent on ADP rather than ticlopidine. In a phase I study performed in Japan, significant inhibition of ADP-induced platelet aggregation and prolongation of bleeding time was observed in the dose range of 25, 50 and 75 mg. These effects were comparable to 200 or 300 mg of ticlopidine. Antithrombotic effects have also been shown in experimental animal models. Clopidogrel is expected to reduce the incidence of neutropenia since smaller doses are sufficient to suppress platelet aggregation compared to ticlopidine. Clopidogrel has been proven to be a potent and well-tolerated antiplatelet agent for atherosclerosis patients at risk of thrombosis, in Europe.
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PMID:[Antiplatelet effect of clopidogrel]. 161 93

The chemistry, pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage of ticlopidine are reviewed. Ticlopidine appears to inhibit platelet aggregation induced by adenosine diphosphate. Ticlopidine hydrochloride is rapidly absorbed after oral administration, and maximum antiplatelet effects occur one to three hours after the dose. In multicenter, randomized, double-blind trials, ticlopidine was more effective than aspirin or placebo in preventing stroke, myocardial infarction, or death caused by vascular events. Ticlopidine was more effective than aspirin in preventing recurrent transient ischemic attacks after six months of therapy. Ticlopidine has also been used to prevent occlusion and improve patency of aortocoronary bypass grafts, to prevent ischemic ulcers in patients with chronic arterial occlusive disease, and to slow the progression of diabetic microangiopathy. The most serious adverse effect, neutropenia, occurred in about 1% of patients. The most frequently reported adverse effects are diarrhea, nausea, vomiting, and abdominal cramps. Ticlopidine is indicated for reducing the risk of thrombotic stroke in patients who have experienced a minor stroke, transient ischemic attack, or completed thrombotic stroke. The recommended dosage is 500 mg/day in two divided doses taken with food. Ticlopidine is an alternative agent for the primary and secondary prevention of stroke. Because of the risk of neutropenia and agranulocytosis and the high cost of therapy, ticlopidine should be reserved for patients who are intolerant of or lack benefit from aspirin.
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PMID:Ticlopidine: a new platelet aggregation inhibitor. 161 11

Carbenicillin and mezlocillin are widely used for treatment of Pseudomonas infections in patients with cancer. Carbenicillin has been reported to cause platelet dysfunction and bleeding diathesis in some individuals. We evaluated whether carbenicillin causes deterioration of platelet function in patients with cancer and whether mezlocillin causes similar effects on platelets from normal subjects or from patients with cancer. In these in vitro studies, carbenicillin and mezlocillin decreased ADP and epinephrine-induced platelet aggregation and thromboxane A2 generation similarly, but only in concentrations of 3.2 mg/ml or higher. In contrast, carbenicillin was more potent than mezlocillin in decreasing ristocetin-induced platelet aggregation. We also evaluated effects of these antibiotics on platelet function in 19 patients with cancer who developed fever and neutropenia. These patients received either mezlocillin (10 patients) or carbenicillin (nine patients) in combination with nafcillin and gentamycin. Neither carbenicillin nor mezlocillin had any significant effect on platelet aggregation or thromboxane A2 generation. Lack of effects in vivo was due to defective platelet function in these patients prior to any antibiotics. These defects were most probably related to underlying disease and/or prior chemotherapy. Thus, carbenicillin and mezlocillin can both safely be used in patients with cancer who develop fever and neutropenia, and neither seems to have advantage over the other in terms of platelet function.
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PMID:Comparative effects of mezlocillin and carbenicillin on platelet function and thromboxane generation in patients with cancer. 278 54

Platelet-activating factor (PAF) is released in vitro during human and rabbit polymorphonuclear neutrophil (PMN) aggregation induced by C5a anaphylatoxin, neutrophil cationic proteins (CP) and their carboxypeptidase-B-derived fragments, C5a des Arg and CP des Arg, as well as phagocytosis of opsonized baker's yeast particles and immune complexes (IC). Purified PAF itself is able to cause in vitro PMN aggregation. By using selective inhibitors, we show that PMN aggregation, induced either by PAF or by other soluble stimuli such as C5a, CP and their des Arg products, follows a similar metabolic pathway, which is both adenosine-diphosphate-(ADP)- and arachidonic acid (AA)- independent. The in vivo injection of purified PAF into rabbits leads both to formation of intravascular PMN aggregates and to development of acute neutropenia, which has the same features as those observed after challenge with IC, C5a and CP. In this respect, electron-microscopic studies of intravascular PMN aggregates in the pulmonary capillary network and glomeruli show identical ultrastructural patterns. Moreover, the intravascular release of PAF is demonstrated after the intravenous injection of IC and temporally correlated with the development of neutropenia. We suggest that PAF is probably the final, common, effector substance of IC-, C5a-, C5a-des-Arg-, CP-, CP-des-Arg-mediated PMN aggregation.
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PMID:Mediators of immune-complex-induced aggregation of polymorphonuclear neutrophils. II. Platelet-activating factor as the effector substance of immune-induced aggregation. 745 Sep 1

Ticlopidine is a powerful antiplatelet activator that inhibits adenosine diphosphate (ADP)-induced platelet aggregation. Its most common side-effects are skin rashes, diarrhea and neutropenia. Aplastic anemia is rare. This paper reports a patient with severe aplastic anemia that developed after the use of ticlopidine. The 85-year-old woman developed fever, chills and chest pain 5 weeks after starting ticlopidine 250 mg twice daily. Severe aplastic anemia was proved by blood examination, bone marrow aspiration and biopsy. In spite of the recovery of absolute neutrophil count to more than 1,000/mm3, 16 days after ticlopidine was stopped and administration of strong antibiotics, the patient died from candidal sepsis.
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PMID:Severe aplastic anemia induced by ticlopidine: report of a case. 852 78

The aim of platelet inhibitory therapy in cardiology is to prevent undesired thrombus formation and, thus, to prevent complications of cardiovascular diseases. In Germany, 5 substances are approved for antiplatelet therapy. Acetylsalicylic acid, an inhibitor of platelet cyclooxygenase, has been shown to be effective at both high and low doses in the secondary prevention of myocardial infarction, coronary heart disease, and cerebrovascular disease. In addition, acetylsalicylic acid is effective in reducing the complications of unstable angina pectoris and coronary angioplasty, and in reducing the occlusion rate of aortocoronary bypass grafts. The addition of dipyridamole to acetylsalicylic acid has not been shown to result in any additional benefit in many clinical studies. Ticlopidine, an antagonist of ADP-induced platelet aggregation has been similarly effective as acetylsalicylic acid in the treatment of coronary heart disease. The principal side effect of the drug, the occurrence of neutropenia in about 1% of treated patients, makes regular blood cell counts mandatory during treatment. In the secondary prevention of cerebrovascular disease, the drug may be superior to acetylsalicylic acid. Trapidil is an anti-platelet substance which acts on platelets through various mechanisms including inhibition of the release of "platelet derived growth factor". In 3 smaller randomized studies, trapidil has been found to reduce the restenosis rate after coronary angioplasty. Abciximab, the Fab-fragment of an antibody against the platelet fibrinogen receptor glycoprotein 11b/IIIa has been shown to be effective in the prevention of acute and long-term complications of high-risk coronary angioplasty.
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PMID:-New aspects in antithrombotic therapy--platelet inhibitors-. 864 75

Clopidogrel is a thienopyridine that irreversibly inhibits platelet aggregation by selectively binding to adenylate cyclase-coupled ADP receptors on the platelet surface. In animal models, clopidogrel reduced the formation of both arterial and venous thrombi. After oral administration, clopidogrel is rapidly absorbed and undergoes metabolic activation in the liver. The principal circulating metabolite is SR 26334, an inactive carboxylic acid derivative. The active metabolite is not yet known. Findings of a large, well controlled study of clopidogrel versus aspirin in patients with atherosclerotic vascular disease (CAPRIE study) indicate that clopidogrel has superior efficacy in terms of prevention of ischaemic stroke, myocardial infarction and vascular death. Clopidogrel-treated patients experienced less frequent gastrointestinal upset, abnormal liver function and gastrointestinal haemorrhage than patients who received aspirin, but more frequent rash and diarrhoea. Neutropenia and thrombocytopenia occurred rarely and at similar rates in both groups.
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PMID:Clopidogrel. 2642 34

Effective antiplatelet drugs--aspirin, ticlopidine, dipyridamole, and clopidogrel--are reviewed. Aspirin has remained the pharmacologic foundation of stroke prevention, primarily because of its low cost. It has been shown to provide a 22% relative risk reduction of stroke in high-risk patients. Its principal adverse effect is gastrotoxicity. Ticlopidine has been widely used in patients with a high risk of stroke who are sensitive to aspirin or in whom aspirin has failed. It has been associated with a median reduction in adenosine diphosphate-induced platelet aggregation of 70% in about 8-11 days. Ticlopidine has been shown to be superior to aspirin at three years in preventing stroke. The principal adverse effects are diarrhea and rash; there has been a 2.4% occurrence of neutropenia. In a trial comparing aspirin, dipyridamole, and a combination of the two, the risk of stroke was 18% lower with aspirin, 16% lower with dipyridamole, and 37% lower with combination therapy compared with placebo. The adverse-effect profile of dipyridamole has proven to be less problematic than that of aspirin or ticlopidine. In a trial comparing clopidogrel with aspirin, patients receiving clopidogrel had an annual 5.32% risk of ischemic stroke, myocardial infarction, or vascular death compared with 5.83% for patients receiving aspirin. Clopidogrel has been associated with a small occurrence of rash and diarrhea, and gastrointestinal intolerance and hemorrhage were less frequent with clopidogrel than with aspirin. Both aspirin and clopidogrel are associated with a low occurrence of neutropenia. Aspirin, ticlopidine, dipyridamole, and clopidogrel have earned a role in stroke prevention; the different adverse-effect profiles of the drugs will influence the choice of agent.
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PMID:Clinical considerations in selecting antiplatelet therapy in cerebrovascular disease. 978 98

Recombinant human thrombopoietin (rHuTPO) serves as a megakaryocyte colony-stimulating factor and predominantly acts on GPIIb/IIIa+ rat late megakaryocyte progenitor cells, colony forming units-megakaryocyte (CFU-MK). The GPIIb/IIIa+ fraction of CFU-MK differentiates into mature megakaryocytes and further into proplatelets in liquid culture containing rHuTPO. rHuTPO stimulates cultured megakaryocytes generated from rat GPIIb/IIIa+ CFU-MK to enhance proplatelet formation and to increase megakaryocyte size. rHuTPO also induces a big size of megakaryocyte colonies from human cord blood CD34+ cells. rHuTPO does not cause aggregation of platelets from normal mice and mice made thrombocytotic by consecutive administration of rHuTPO, but preincubation with rHuTPO enhances adenosine diphosphate-induced aggregation, suggesting that platelets induced by rHuTPO administration may have a normal function. Administration of rHuTPO to normal mice daily for five days causes a dose-dependent thrombocytosis. On the other hand, rHuTPO induces a significant decrease in hemoglobin concentration and does not affect white blood cell counts. rHuTPO increases the size and number of marrow megakaryocytes and the number of marrow CFU-MK, and also influences the development of other hematopoietic progenitor cells. The effects of rHuTPO on thrombocytopenia associated with myelosuppression were examined in animal models. Following treatment with mitomycin C, mice received daily injections of various doses of rHuTPO. rHuTPO reduced the severity of thrombocytopenia, accelerated the recovery of platelets and improved neutropenia. Similar therapeutic efficacy was observed in cynomolgus monkeys treated with nimustine. These results suggest the clinical usefulness of rHuTPO for the treatment of thrombocytopenia.
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PMID:Physiologic role of TPO in thrombopoiesis. 1101 13

Aspirin inhibits platelet activation by irreversibly inhibiting platelet cyclooxygenase and thromboxane production, and reduces the odds of serious vascular events (stroke, myocardial infarction or vascular death) by about one quarter in a range of patients with symptomatic atherosclerosis at high risk of a subsequent event. The adenosine diphosphate (ADP) receptor antagonists clopidogrel and ticlopidine are significantly more effective than aspirin in high-risk vascular patients, further reducing the odds of serious vascular events by about 10% (95% CI 2-19%) over the benefit provided by aspirin. The ADP receptor antagonists are also associated with a significant 30% reduction in the odds of gastrointestinal haemorrhage (odds ratio 0.71, 95% CI 0.59-0.86). Ticlopidine increases the odds of skin rash and of diarrhoea by more than twofold compared with aspirin, whereas clopidogrel is associated with a one-third increase in the odds of rash and of diarrhoea. Only ticlopidine increases the odds of neutropenia compared with aspirin. There is no clear evidence as yet for the benefit of dipyridamole or an oral GP IIb/IIIa receptor antagonist as single antiplatelet agents in atherothrombotic patients. Amongst high vascular risk patients, the combination of low-dose aspirin and high-dose dipyridamole is associated with about a 10% (95% CI 0-20%) reduction in the odds of a serious vascular event. Most of this reduction is due to a 23% reduction in non-fatal stroke. The size of this estimate continues to be investigated in an ongoing study of patients with transient ischaemic attack and stroke. The combined use of aspirin and ticlopidine is markedly superior to heparin, warfarin and aspirin for reducing thrombotic complications after coronary artery stenting. Clopidogrel plus aspirin has been shown to be safer than aspirin and ticlopidine in coronary stenting, and is now under long-term evaluation in unstable angina, and other conditions in which patients are at high risk of atherothrombotic events.
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PMID:Current oral antiplatelet agents to prevent atherothrombosis. 1131 17


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