The Effects Of Ticlopidine Hydrochloride On Bleeding Time And Platelet Function In Man

1981 ◽  
Author(s):  
D J Ellis ◽  
R L Roe ◽  
J J Bruno ◽  
B J Cranston ◽  
M M McSpadden

Ticlopidine hydrochloride (T) was given to healthy male and female subjects in doses ranging from 125-500 mg/day for up to 8 days to study the rate of onset and offset of action and to define the optimal dosage for inhibition of platelet function tests.Template bleeding time (BT) using the Simplate® device and ex vivo platelet aggregation were done every day from the start of dosing through the post-dosing period until platelet function had returned to baseline.Achievement of maximal bleeding time prolongation and maximal inhibition of platelet aggregation induced by ADP, collagen, and epinephrine required 3-5 days of dosing. Rate of onset was higher at higher drug doses. Post-dose return to baseline took 4-8 days.BT prolongation was dose-dependent with 2.0 × prolongation at 125 mg/d, 2.5 × at 250 mg/d, 3.4 × at 375 mg/d and 4.7 × at 500 mg/d.At steady state, ADP aggregation (1st and 2nd phase) was inhibited by 50-60%, epinephrine aggregation was inhibited by 40-80%, and collagen aggregation was inhibited by 5580%. Inhibition was dose-dependent. Arachidonic acid (1 × 10-3M) induced aggregation was not inhibited. ATP release during collagen aggregation was inhibited by 20-50% and malondialdehyde production induced by thrombin was inhibited 20-55%, both in a dose-related fashion.Ticlopidine hydrochloride is a potent inhibitor of platelet function with a broad spectrum of activity and a delayed onset and offset of action. The drug is neither a prostaglandin synthetase nor a phosphodiesterase inhibitor and appears to act by a novel mechanism.

2021 ◽  
Vol 12 ◽  
Author(s):  
Gang Liu ◽  
Zhaowei Yuan ◽  
Xiaoyun Tian ◽  
Xiuqin Xiong ◽  
Fang Guo ◽  
...  

Pimpinellin is a coumarin-like compound extracted from the root of Toddalia asiatica. Its effects on platelet function has not been investigated. This study found that pimpinellin pretreatment effectively inhibited collagen-induced platelet aggregation, but did not alter ADP- and thrombin-induced aggregation. Platelets pretreated with pimpinellin showed reduced α granule (CD62) level and secretion of dense granule (ATP release). Pimpinellin-treated platelets also exhibited decreased clot reaction and TxB2 production. Pimpinellin pretreatment suppressed adhesion and spreading of human platelets on the fibrinogen coated surface. Analysis of tail bleeding time of mice administered with pimpinellin (40 mg/kg) revealed that pimpinellin did not change tail bleeding time significantly, number of blood cells, and APTT and PT levels. Pimpinellin inhibited collagen-induced ex vivo aggregation of mice platelets. Immunoblotting results showed that pimpinellin suppressed collagen-induced phosphorylation of PI3K-Akt-Gsk3β and PKC/MAPK in platelets.


1992 ◽  
Vol 68 (05) ◽  
pp. 500-505 ◽  
Author(s):  
Ch M Samama ◽  
Ph Bonnin ◽  
M Bonneau ◽  
G Pignaud ◽  
E Mazoyer ◽  
...  

SummaryWe investigated the comparative antithrombotic properties of clopidogrel, an analogue of ticlopidine, and aspirin, using the Folts' model on femoral arteries in 22 pigs. On each animal, clopidogrel or aspirin were used to treat the thrombotic process on the left femoral artery and to prevent this process on the right femoral artery. Sequentially: an injury and stenosis were carried out on the left femoral artery; the thrombotic process was monitored with a Doppler during a 30-min observation period for cyclic flow reductions or permanent cessation of flow; after the first cyclic flow reduction occurred, clopidogrel (5 mg kg-1) or aspirin (2.5, 5, 100 mg kg-1) were injected intravenously; if cyclic flow reductions were abolished, epinephrine (0.4 µg kg-1 min-1) was injected to try to restore cyclic flow reductions and/or permanent cessation of flow; then injury and stenosis were applied on the right femoral artery. Before and after injection of clopidogrel or aspirin, ear immersion bleeding times and ex-vivo platelet aggregation were performed. Clopidogrel (n = 7) abolished cyclic flow reductions in all animals and epinephrine did not restore any cyclic flow reduction. On the right femoral artery, cyclic flow reductions were efficiently prevented, even for two injuries. Basal bleeding time (5 min 28) was lengthened (>15 min, 30 min after clopidogrel and remained prolonged even after 24 h). ADP-induced platelet aggregation was inhibited (more than 78%). Comparatively, aspirin had a moderate and no dose-dependent effect. Aspirin 2.5 mg kg-1 (n = 6) abolished cyclic flow reductions in 2 animals, CFR reoccurred spontaneously in one animal and epinephrine restored it in a second animal. Aspirin 5 mg kg-1 (n = 6) abolished cyclic flow reductions in only 3 animals and epinephrine always restored it. Aspirin 100 mg kg-1 (n = 3) was unable to abolish cyclic flow reductions. On the right femoral artery, aspirin did not significantly prevent cyclic flow reductions which occurred in all animals after one (n = 14) or two injuries (n = 1), except for one animal. Basal bleeding time was lengthened but it shortened rapidly, reaching its basal value after 24 h. ADP-induced aggregation was not significantly inhibited, whereas arachidonic acid induced aggregation was always inhibited. Clopidogrel appears as a more potent antithrombotic drug than aspirin in this model, in treating and preventing spontaneous or epinephrine-induced cyclic flow reductions and lengthening bleeding time.


1981 ◽  
Author(s):  
E E Nishizawa ◽  
B A Molony ◽  
M M Meinzinger ◽  
D J Williams

It has been reported that although ASA may have some beneficial effects in males, no differences from placebo was detected in females in clinical trials on venous thrombosis, TIA and stroke. Since ASA inhibits platelet function and because the end-points measured in the above clinical studies may be related to platelet function, we measured bleeding time and platelet aggregation induced by collagen or arachidonic acid following oral administration of ASA (650 mg) or flurbiprofen (100 mg) in normal male and female volunteers (10 per group, total of 40 subjects) between the age of 50 and 70.No sex-associated differences in response with either drug were observed in bleeding time or platelet function. Thus, we were unable to confirm that the observation of beneficial effect of ASA in males was due to its effect on platelets. However, more interestingly there was a statistically shorter bleeding time in males (p = 0.026) before administration of drug. It was also found that despite the normal response to collagen, PRP prepared from pre-drug blood samples from 6 individuals (15%) did not aggregate when stimulated with arachidonic acid at concentrations as high as 1 mM. These results suggest that, at least in some individuals, collagen-induced aggregation may proceed by a pathway independent of the arachidonic acid pathway.


2006 ◽  
Vol 96 (08) ◽  
pp. 167-175 ◽  
Author(s):  
Yutaka Matsumoto ◽  
Hisao Takizawa ◽  
Kazuhiro Nakama ◽  
Xiaoqi Gong ◽  
Yoshihisa Yamada ◽  
...  

SummaryRecent progress in the understanding of thrombus formation has suggested an important role of glycoprotein (GP)VI. In contrast to its pivotal role in collagen-induced platelet activation, it has been suggested that its blockade does not induce massive bleeding tendency. To demonstrate the dissociation between inhibitory effect on platelet aggregation and bleeding by GPVI blockade, we examined the effects of Fab fragment of OM2, an anti-human GPVI monoclonal antibody on ex vivo collagen-induced platelet aggregation and skin bleeding time after intravenous injection in cynomolgus monkeys. In a dose-escalation study, OM2 potently (>80%) inhibited collagen-induced platelet aggregation at the cumulative dose of 0. 2 mg/kg with a slight prolongation of bleeding time (1. 3 times baseline value). Furthermore, at 18. 8 mg/kg, the highest dose tested, prolongation of bleeding time was still mild (1. 9 times). In contrast, abciximab, Fab fragment of anti-GPIIb/IIIa antibody prolonged bleeding time by 5. 0 times at 0. 35 mg/kg, the lowest effective dose on platelet aggregation. Ina pharmacodynamic study,a bolus injection of OM2 at 0. 4 mg/kg produced potent inhibition of collagen-induced aggregation up to six hours after injection, showing longer half-life than that of abciximab. The injection of OM2 Fab did not induce thrombocytopenia and GPVI depletion in monkeys. These results suggest that blockade of GPVI by antibody can exerta potent inhibitory effect on collagen-induced platelet aggregation with a milder prolongation of bleeding time than blockade of GPIIb/IIIa. This study indicates that OM2 has the potential to be developed as a new class of therapeutic tool.


1987 ◽  
Author(s):  
M Thomas ◽  
P Lumley ◽  
P Ballard ◽  
J R O'Brien

In-vitro GR32191 is a potent and specific thromboxane receptor blocking drug on platelets, and vascular and airways smooth muscle (Lumley et al this meeting). We have undertaken studies in healthy male subjects (n) to examine the effects of oral GR32191 upon platelet aggregation ex-vivo and template bleeding time. Platelet aggregation was monitored in whole blood by counting platelets electronically. Concentration-effect curves to U-46619 and ADP were constructed prior to and following drug or placebo. The degree of rightward displacement of a curve due to treatment was expressed as a concentration-ratio (CR) which was calculated at the 50% aggregation level (ECso post-treatment ECso pre-treatment). Plasma concentrations of GR32191 were determined by h.p.l.c. After single doses of GR32191 mean peak CR's of 8 and 80 were achieved with 0.125 and 0.25mg/kg (n=4) and values of 74 and 234 with 0.5 and lmg/kg (n=4). Peak effects were seen within 2 hours of dosing while activity was still present between 8 and 24 hours. ADP-induced aggregation was unaffected by drug (CR<2) and placebo was without significant effect upon the sensitivity to either aggregating agent (CR<2). GR32191 was rapidly absorbed and the plasma elimination half-life was about 2 hours. GR32191 17.5mg 12-hourly for 10 days (n=6) produced a progressive antagonism of U-46619 induced aggregation which resulted in a large continuous blockade in all subjects (range of 12htrough CR's 85 to 287). However, plasma concentrations of GR32191 did not accumulate on repeated administration. In a double-blind, placebo-controlled, cross-over study (n=16), a statistically significant (p= 0.002) increase in bleeding time was seen following treatment with GR32191 40mg twice daily for 7 days (pre-treatment mean 3.79 min, post-placebo mean 3.47 min, post-GR32191 mean 5.42 min). Rectal bleeding (n=l) has occurred with GR32191 but otherwise tolerability has been good. No drug related changes have been seen in routine laboratory safety screens. Clinical studies are in progress.


1994 ◽  
Vol 72 (06) ◽  
pp. 912-918 ◽  
Author(s):  
M Gawaz ◽  
I Ott ◽  
A J Reininger ◽  
F-J Neumann

SummaryMagnesium deficiency and its association with platelet hyperreactivity has been well recognised in a variety of diseases including myocardial infarction, preeclampsia, and diabetes. In order to investigate potential effects of intravenous Mg2+ supplementation, platelet function was studied by measurements of in vitro bleeding time (BT) and of fibrinogen (Fg)-mediated aggregation of washed platelets. In addition, the effect of Mg2+ on platelet adhesion onto immobilised Fg, on Fg binding to activated platelets, and on surface expression of GMP-140 or GP53 was evaluated. Mg2+(4 mM) prolonged in vitro BT by 30% and inhibited Fg-mediated aggregation significantly, independent of the agonist used to initiate platelet aggregation (ADP, collagen, epinephrine, thrombin, phorbol ester). Adhesion of resting platelets to immobilised Fg was reduced by 50% in the presence of 2 mM Mg2+. Moreover, Mg2+ reduced Fg binding to ADP- or collagen-stimulated platelets as well as surface expression of GMP-140 with an IC50 of approximately 3 mM. Intravenous administration of Mg2+ to healthy volunteers inhibited both ADP-induced platelet aggregation (p <0.05) by 40% and binding of Fg or surface expression of GMP-140 by 30% (p <0.05). Thus, pharmacological concentrations of Mg2+ effectively inhibit platelet function in vitro and ex vivo.


1979 ◽  
Vol 41 (02) ◽  
pp. 425-435 ◽  
Author(s):  
Fernando B Ubatuba ◽  
Salvador Moncada ◽  
John R Vane

SummaryProstacyclin (PGI2) infused intravenously into anaesthetized rabbits inhibited electrically-induced thrombus formation in the carotid artery, increased bleeding time and inhibited ex vivo platelet aggregation induced by ADP or arachidonic acid. The increase in bleeding time and the inhibition of ex vivo platelet aggregation lasted for as long as the infusion of PGI2 was maintained but rapidly disappeared after infusion was stopped.Prostacyclin is a more potent inhibitor of platelet function, in vivo than prostaglandin E1 (PGE1) or prostaglandin D2 (PGD2).The effects of prostacyclin on all parameters studied except blood pressure were potentiated by the concomitant administration of theophylline, a phosphodiesterase inhibitor.


1994 ◽  
Vol 72 (01) ◽  
pp. 119-124 ◽  
Author(s):  
Juerg F Tschopp ◽  
Curt Mazur ◽  
Kenneth Gould ◽  
Raymond Connolly ◽  
Michael D Pierschbacher

SummaryMembrane glycoprotein αIIbβ3 on platelets plays a pivotal role in hemostasis by mediating RGD-(arginine-glycine-aspartic acid)-dependent platelet adhesion and aggregation. Antagonists of αIIbβ3 ligand binding function, such as antibodies, snake venom peptides, or synthetic RGD-containing peptides can completely inhibit platelet aggregation in vitro and cause significant prolongation of bleeding times when injected into experimental animals. The in vitro and in vivo properties of an αIIbβ3 specific RGD-containing peptide 2G (G(Ten)GHRGDLRCA) were compared to two non-specific RGD-containing peptides IN (G(Pen)GRGDTPCA) and 2H (GRGDSPDG). All three peptides have similar IC50 values in human patelet aggregation (14-22 μM) and ELISA-based μIIbβ3 receptor assays (0.2–0.3 αM) but show different inhibitory activity (IC50 values) in the αv㯂5 (2G = 10 μM; IN = 0.06 μM; 2H = 0.05 μM) and receptor assays (2G = 8.3 μM; IN = 0.06 μM; 2H = 0.04). The αIIbβ3 specific peptide 2G had no effect on monolayers of human saphenous vein endothelial cells while IN and 2H caused many cells to detach and contract. Peptides 2G and IN inhibited ADP-stimulated ex vivo platelet aggregation in dogs in a dose dependent manner. When complete inhibition (>90%) of ex vivo platelet aggregation was achieved with either a 10 mg/kg bolus followed by a 16mg/kg/h infusion of 2G or with a 15 mg/kg bolus and 24 mg/kg/h infusion of IN, peptide IN caused a dose-dependent increase of the template bleeding time, while peptide 2G had no effect, even at doses up to 15 mg/kg bolus followed by 24 mg/kg/h infusion. The in vivo properties of peptides 2G and 2H were also examined in a baboon ex vivo shunt model for their ability to block platelet uptake and fibrinogen deposition on small caliber GORE-TEX® grafts and for their effect on the hemostatic system. Systemic administration of peptide 2G at 10 mg/kg bolus followed by 10 mg/kg/h infusion (or at a 2-fold lower dose) abolished platelet uptake and fibrinogen deposition on the graft surface without affecting the hemostasis and template bleeding time of the animal. By contrast, peptide 2H caused a 3-4-fold increase in bleeding time at a dose of 10 mg/kg. The results suggest that efficacy and the effect of specific aIIbp3antagonists on bleeding time can be separated and that selective aIIbP3 receptor blockade may be an efficient and safe approach to improve the patency and the success rate pf small caliber vascular grafts and to treat unwanted platelet-dependent thromboses. While peptide 2G may represent a unique class of antithrombotic agent, the clinical use of this type of molecule would require a significant enhancement in potency.


1987 ◽  
Author(s):  
M P Gordge ◽  
R W Faint ◽  
P B Rylance ◽  
G H Neild

The bleeding tendency of uraemia may be related to reduction by anaemia of erythrocyte/platelet interaction, toxic inhibition of platelet aggregation and abnormal von Willebrand Factor (vWF) mediated platelet adhesion. Our aim in this study was to determine at what stage of renal failure bleeding time becomes prolonged and to investigate the mechanisms involved.We have measured bleeding time (Simplate II), plasma levels of fibrinogen and vWF, and ex-vivo platelet responsiveness in 31 patients with chronic renal failure (CRF) of various degrees of severity and compared them with values obtained in 22 healthy controls. No patient was dialysed, nephrotic or suffering from immunological renal disease. Patients were divided into mild (plasma creatinine <300 umol/1), n=10, moderate (300-600 umol/1), n=14, or severe (>600 umol/1), n=7, CRF.Bleeding time became significantly prolonged only in severe CRF (p<0.005). Haematocrit fell as renal failure advanced, and correlated with bleeding time (r=0.40, p<0.05). Platelet counts were normal. Platelet aggregation in response to ristocetin (mediated by vWF) and ADP increased progressively (p<0.005 in severe CRF), as did spontaneous aggregation (p<0.005 in severe CRF). This was associated with an increase in plasma vWF and fibrinogen (p<0.005 in severe CRF). Collagen induced aggregation was slightly, but not significantly increased. Thromboxane (TxB2) generation in clotting blood was the only measurement that showed a reduced platelet response (p<0.025 in severe CRF).In summary, a bleeding tendency develops late in the course of progressive CRF when plasma creatinine has risen to at least 600 umol/1. Platelet aggregation is enhanced rather than reduced and platelet interaction with vWF is not defective. Anaemia appears more important than abnormal platelet aggregation in mediating uraemic bleeding, although reduced serum TxB2 generation suggests a defect in platelet response to endogenous thrombin which may also contribute. Increased platelet aggregation and fibrinogen concentrations might promote glomerular thrombosis and contribute to the progression of CRF.


1994 ◽  
Vol 71 (01) ◽  
pp. 095-102 ◽  
Author(s):  
Désiré Collen ◽  
Hua Rong Lu ◽  
Jean-Marie Stassen ◽  
Ingrid Vreys ◽  
Tsunehiro Yasuda ◽  
...  

SummaryCyclic Arg-Gly-Asp (RGD) containing synthetic peptides such as L-cysteine, N-(mercaptoacetyl)-D-tyrosyl-L-arginylglycyl-L-a-aspartyl-cyclic (1→5)-sulfide, 5-oxide (G4120) and acetyl-L-cysteinyl-L-asparaginyl-L-prolyl-L-arginyl-glycyl-L-α-aspartyl-[0-methyltyrosyl]-L-arginyl-L-cysteinamide, cyclic 1→9-sulfide (TP9201) bind with high affinity to the platelet GPIIb/IIIa receptor.The relationship between antithrombotic effect, ex vivo platelet aggregation and bleeding time prolongation with both agents was studied in hamsters with a standardized femoral vein endothelial cell injury predisposing to platelet-rich mural thrombosis, and in dogs with a carotid arterial eversion graft inserted in the femoral artery. Intravenous administration of G4120 in hamsters inhibited in vivo thrombus formation with a 50% inhibitory bolus dose (ID50) of approximately 20 μg/kg, ex vivo ADP-induccd platelet aggregation with ID50 of 10 μg/kg, and bolus injection of 1 mg/kg prolonged the bleeding time from 38 ± 9 to 1,100 ± 330 s. Administration of TP9201 in hamsters inhibited in vivo thrombus formation with ID50 of 30 μg/kg, ex vivo platelet aggregation with an ID50 of 50 μg/kg and bolus injection of 1 mg/kg did not prolong the template bleeding time. In the dog eversion graft model, infusion of 100 μg/kg of G4120 over 60 min did not fully inhibit platelet-mediated thrombotic occlusion but was associated with inhibition of ADP-induccd ex vivo platelet aggregation and with prolongation of the template bleeding time from 1.3 ± 0.4 to 12 ± 2 min. Infusion of 300 μg/kg of TP9201 over 60 min completely prevented thrombotic occlusion, inhibited ex vivo platelet aggregation, but was not associated with prolongation of the template bleeding time.TP9201, unlike G4120, inhibits in vivo platelet-mediated thrombus formation without associated prolongation of the template bleeding time.


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