Platelet survival in patients treated with ticlopidine following reconstructive arterial surgery

Effect of ticlopidine on blood loss, platelet turnover and platelet deposition on prosthetic surfaces in patients undergoing aorto-femoral bypass grafting

Sixty patients in whom a prosthetic aorto-femoral bypass graft was inserted were pretreated with ticlopidine (250 mg b.i.d.) or placebo in a double-blind study. Blood loss and transfusion need were higher in ticlopidine treated patients. Platelet survival was partially corrected and platelet deposition on prosthetic surfaces was inhibited with ticlopidine. The study suggests that ticlopidine does not increase excessively the bleeding risk during peripheral vascular surgery and that the antiplatelet drug may have beneficial effects in the early phase after insertion of prosthetic vascular graft.

Ticlopidine inhibits platelet thrombus formation studied in a flowing system

We have studied the effect of ticlopidine on platelet function. This effect was assessed by aggregation studies and by the Baumgartner perfusion system as an ex vivo approach to study modifications in the interaction of platelets with vascular subendothelium. Platelets from volunteers, that were given 250 mg of ticlopidine twice a day showed a significantly decreased aggregation of platelets induced by several agonists. In the perfusion studies a marked reduction in the parameters that measure platelet interaction with subendothelium was also observed. The decrease in thrombus formation, and the diminished size of platelet aggregates, clearly indicated that ticlopidine impaired platelet-platelet interaction in this experimental flowing system. Our results suggest that ticlopidine is a potent inhibitor of platelet function and that its antiplatelet activity might be related to the mechanisms that regulate the interaction between platelets at the membrane level.

Therapy of atherosclerotic arteriopathy of lower limbs. Aspects and results

As far as therapy is concerned, atherosclerotic arteriopathy may be divided into acute and chronic forms. In acute embolic forms, therapy should be surgical. Only in cases of peripheral embolism or polyembolism, and in rare cases for which vascular surgery cannot be adopted, can thrombolysis be carried out with UK. In acute thrombotic forms, therapy should be medical, because a thrombus of recent formation is rich in fibrin and may be lyzed by UK. Total recanalization takes place in 61% of cases treated, partial recanalization in 23%. Subsequently perviousness is maintained by adequate antithrombotic therapy. In chronic arteriopathy, the thrombus is lacking or almost lacking in fibrin and thrombolytic therapy is not indicated. Special therapeutic combinations are used containing platelet inhibitors (ticlopidine), antifibrin drugs (subcutaneous heparin), minor fibrinolytic agents (mesoglycan) and hemorheological drugs (pentoxyphylline). This therapy seems to give good results, as showed by the low percentage in amputation calculated on 2,565 patients treated and kept under observation for 5 years. Finally let us consider chronic progressive arteriopathy. This term indicates a very advanced stage, characterized by a gradual irreversible change for the worse leading towards gangrene. As a last resort, before amputating, a thrombolytic therapy with UK was tried to see if with strong fibrinolysis continued for 3 days amputation might be avoided. In a pilot study carried out on 12 patients, the angiographic data showed only partial lysis in small arteries or arterial branches. Clinical data showed reduction or disappearance of pain at rest in 80% of cases. In 70% of cases gangrene disappeared if it was initial and superficial, it was delimited if already in progress.

Effect of ticlopidine on platelet aggregation, adherence to damaged vessels, thrombus formation and platelet survival

Ticlopidine (100 mg/kg/day or 400 mg/kg/day) was administered to rats and rabbits for 48 hr before and during the experiments. Aggregation studies of twice-washed platelets resuspended in Tyrode solution containing apyrase and 0.35% albumin showed that inhibition by ticlopidine of aggregation induced by ADP, collagen, sodium arachidonate or thrombin persisted after resuspension, as did inhibition of the release of 14C-serotonin from prelabeled platelets. Thus the inhibitory effect of ticlopidine or its metabolite is not readily reversed. In both species, ticlopidine prolonged platelet survival when it had been shortened by the insertion of an indwelling aortic catheter, although only the higher dose was effective in rabbits. In this species, this dose also prolonged platelet survival in sham-operated animals. Ticlopidine did not have a significant effect on the clearance of rabbit platelets when their survival had been shortened by pretreatment with neuraminidase. Ticlopidine did not affect the number of 51Cr-labeled platelets that accumulated on the injured vessel wall in rats with indwelling aortic catheters or the amount of thrombus that formed around the catheters in the aortas of the rabbits. It also did not affect the accumulation of platelets in vivo on rabbit aortas de-endothelialized with a balloon catheter. Thus, although ticlopidine inhibited platelet aggregation and release and prolonged shortened platelet survival, it did not inhibit platelet adherence to the damaged wall or thrombosis caused by chronic arterial injury. It is evident that effects on platelet survival and thrombosis do not correlate. The reason for the prolongation of platelet survival is unknown.

Failure of ticlopidine to inhibit deposition of indium-111-labeled platelets on Dacron prosthetic surfaces in humans

In a randomized double-blind trial we sought to determine whether short-term therapy with ticlopidine (250 mg bid for 14 days) inhibited platelet deposition on Dacron aortic bifurcation grafts that had been in place a year or longer. A total of 10 men, 42 to 69 years old, underwent indium-111 platelet imaging during both placebo and drug phases of the trial at 24, 48, and 72 hr after the injection of labeled platelets. Platelet accumulation was quantitated by a graft/blood ratio that compared background-corrected activity of indium-111-labeled platelets in the graft with whole-blood activity of indium-111-labeled platelets. Additionally, blinded qualitative visual analysis of the unprocessed images was used to compare graft area activity with activity in adjacent native arteries. Ticlopidine significantly prolonged the template bleeding time from 5.3 +/- 0.5 to 17.1 +/- 3.1 min (+/- SEM) (p = .003). However, by quantitative analysis there was no significant reduction in platelet deposition in the graft during ticlopidine therapy compared with placebo at 24 hr (graft/blood ratio 2.3 +/- 0.4 vs 2.6 +/- 0.3), 48 hr (3.1 +/- 0.5 vs 3.2 +/- 0.4), or 72 hr (3.9 +/- 0.7 vs 4.0 +/- 0.6) after injection of labeled platelets. By visual analysis, nine patients had positive results for abnormal platelet deposition when on placebo that were unchanged when on ticlopidine. The tenth patient had an equivocal result for abnormal platelet deposition when on placebo and a negative result for abnormal platelet deposition when on ticlopidine.(ABSTRACT TRUNCATED AT 250 WORDS)