Effect of sulfinpyrazone on platelet survival time in patients with transient cerebral ischemic attacks

The Effect of Chloroquine on Circulating Platelet Survival in the Rat

BACKGROUND: Chloroquine inhibits platelet aggregation. Because platelet aggregation may lead to the lysis of platelets, the effect of chloroquine administration on circulating platelet survival was studied. METHODS AND RESULTS: Platelets harvested from the blood of male inbred (WAG) rats were labeled with (111)Indium oxine and returned to other inbred rats. At timed intervals, blood samples were drawn from the rats and taken for radioactivity estimation. In some experiments, the rats (n = 10) received chloroquine (10 mg/kg) intraperitoneally daily for 3 days. Control rats (n = 10) received chloroquine (10 mg/kg) intraperitoneally daily for 3 days. Control rats (n = 10) received normal saline. Indium-labeled platelets disappeared exponentially in control and test rats. The fraction of indium disappearing/h was significantly less in chloroquine-treated rats than in control rats (0.0368 +/- 0.0016 vs 0.0520 +/- 0.0016, mean +/- SEM; P <.001). In all, 99% of the labeled platelets disappeared in 5.3 days in chloroquine-treated rats and 3.7 days in control rats. CONCLUSIONS: Chloroquine administration increases the life span of circulating platelets in rats. If the results are confirmed in humans, chloroquine may prevent the shortened platelet survival and thrombocytopenia common in malarial infection and other thrombotic disorders.

Platelet aggregation inhibitors in neurology

This literature review reports on secondary prevention of ischaemic stroke. The aim of secondary prevention is to protect patients who belong to a risk group from the occurrence of brain infarction. Symptomatic patients with a demonstrated carotid artery stenosis of 70% and more will most probably benefit from carotid endarterectomy if performed by a skilled surgeon in the absence of contraindications. Oral anticoagulant drugs play a minor role in the medical prevention of brain infarction. Antiplatelet drugs, however, have been in use for almost two decades and (meta-)analysis of clinical trials points to acetylsalicylic acid as a drug with a modest but certain contribution of about 15% in the endpoint reduction, even at lower dosages. The addition of dipyridamole to classic acetylsalicylic acid dose appears to increase the endpoint reduction to 30%. Neither dipyridamole nor sulfinpyrazone as monotherapy have been demonstrated to be efficacious in the secondary prevention of ischaemic stroke. Ticlopidine seems a promising alternative for acetylsalicylic acid in those patients who suffer adverse effects from acetylsalicylic acid. Ticlopidine itself, however, has a number of side-effects that limit its application. New clinical trials are under way in order to improve the efficacy of drug treatment in the secondary prevention of brain infarction.

Lack of influence of low-dose acetylsalicylic acid (100 mg daily) on platelet survival time, beta-thromboglobulin and platelet factor 4 in patients with peripheral arterial occlusive disease

In this study we investigated the influence of low-dose (100 mg daily) acetylsalicylic acid (ASA) on 111-In-platelet survival time (PST) and on plasma levels of beta-thromboglobulin (beta-TG) and platelet factor 4 (PF 4) in 30 patients (median age: 60 years) with arteriographically proven peripheral arterial occlusive disease in a chronic stable phase. We observed no significant changes of PST during therapy with ASA (weighted mean: 169.8----166 [median] hours; multiple hit: 168.3----170.6 hours), and also the plasma levels of beta-TG (median: 31.8----32.3 ng/ml) and of PF 4 (3.6----3.9 ng/ml) remained unchanged.

Reproducibility of platelet survival time measurements in patients with peripheral arterial occlusive disease

In this study we investigated the reproducibility of 111-In-platelet survival time (PST) measurements and of plasma levels of beta-thromboglobulin (beta-TG) and platelet factor 4 (PF 4) in 30 patients (median age: 60.5 years) with arteriographically proven peripheral arterial occlusive disease (PAOD) in a chronic stable phase. PST calculated by both the weighted mean - WM - (1. investigation: 187.1 [median] hours - repeat investigation: 188.3 hours) and multiple hit - MH - model (181.4----177.4 hours) demonstrated only a small spontaneous variation. The median coefficient of variation (CV) was 3.0 (WM) and 3.2 (MH), respectively. The reproducibility of beta-TG (CV: 6.1) was also satisfactory. We conclude that the good reproducibility of PST and plasma levels of beta-TG make them well suited to judge the influence of platelet-suppressant drugs on these parameters in patients with PAOD.

Influence of acetylsalicylic acid (1.0 g/day) on platelet survival time, beta-thromboglobulin and platelet factor 4 in patients with peripheral arterial occlusive disease

In this study we investigated the influence of acetylsalicylic acid (ASA) 1.0 g/day on 111-In-platelet survival time (PST) and on plasma levels of beta-thromboglobulin (beta-TG) and platelet factor 4 (PF 4) in 37 patients (median age: 63.4 years) with arteriographically proven peripheral arterial occlusive disease (PAOD) in a chronic stable phase. We found a slight but significant increase of PST during therapy with ASA (weighted mean (WM): 184.3----193.2 [median] hours, p less than 0.05; multiple hit (MH): 182.4----192.8 hours, p less than 0.005) for the total group of patients. Concerning the influence of risk factors of PAOD on PST during ASA-therapy, there was a significant increase of PST only in the nondiabetics (WM: 180.3----204.6 hours, p less than 0.01; MH: 176.8----195.3 hours, p less than 0.01). There was a negative correlation between the baseline values of PST and their increase following ASA therapy (WM: r = -0.63; p less than 0.0001; MH: r = -0.61, p less than 0.0001). The pretreatment levels of beta-TG--but not PF 4--were significantly (p less than 0.001) elevated compared to healthy controls. Therapy with ASA caused a significant decrease in the plasma levels of beta-TG (median: 30.4----26.6 ng/ml, p less than 0.001) and PF 4 (2.95----2.2 ng/ml, p less than 0.01).

Aspirin and other antiplatelet drugs in the prophylaxis of thrombosis

Aspirin is of proven value as an antithrombotic drug. In unstable angina it reduces the risk of death and myocardial infarction by half. After a myocardial infarction it reduces the risk of death by about 10% and of coronary incidence (coronary death or definite myocardial infarction) by about 25%. These effects appear to be additive with those of beta-blocking drugs. Aspirin also reduces the risk of occlusion of aortocoronary saphenous vein grafts by about half. In transient cerebral ischaemia, aspirin may reduce the risk of stroke and death by 50%. In most clinical trials to date the daily dose of aspirin ranges from 325 mg to 1400 mg. Interest in very low doses of aspirin (less than 60 mg daily) is considerable but has yet to be translated into proven clinical benefit. Dipyridamole has not been shown to be effective as an antithrombotic when used alone. Its antiplatelet action ex vivo may be enhanced by combination with aspirin but clinical trials have shown relatively little advantage of the combination over aspirin alone. Sulphinpyrazone has not become established as a first line antithrombotic drug. Epoprostenol is useful in extracorporeal circulations to prevent platelet consumption and possibly in severe inoperable peripheral vascular disease.

Effects of platelet-modifying drugs on arterial thromboembolism in baboons. Aspirin potentiates the antithrombotic actions of dipyridamole and sulfinpyrazone by mechanism(s) independent of platelet cyclooxygenase inhibition

To resolve questions of drug actions, efficacy, and interactions for platelet-modifying agents used clinically, we have compared the relative capacities and mechanisms of aspirin, dipyridamole, sulfinpyrazone, and dazoxiben to prevent arterial thromboembolism in a baboon model. In 136 studies the agents were given twice daily by oral administration both singly and in combination. The antithrombotic efficacy of a given therapy was determined by its capacity to interrupt steady-state platelet utilization induced by thrombogenic arteriovenous cannulae. When given alone, dipyridamole and sulfinpyrazone reduced the rate at which platelets were utilized by thrombus formation in a dose-dependent manner with essentially complete interruption by dipyridamole at 10 mg/kg per d. In contrast, neither aspirin (2-100 mg/kg per d) nor dazoxiben (20-100 mg/kg per d) decreased cannula platelet consumption detectably despite the striking reduction in the capacity of platelets to produce thromboxane B2. However, aspirin, but not dazoxiben, potentiated the antithrombotic effects of dipyridamole and sulfinpyrazone in a dose-dependent fashion without changing the pharmacokinetics for any of the agents. Complete potentiation required aspirin at 20 mg/kg per d to be given with each dose of dipyridamole. Because dazoxiben's blockade of platelet thromboxane A2 production was not associated with antithrombotic potentiation, and because complete potentiation by aspirin required a dose that fully inhibited vascular production of prostaglandin I2 (PGI2), we conclude that aspirin's potentiating effect on dipyridamole is independent of PGI2 production or inhibition of thromboxane A2 formation. In addition, because frequent repeated and synchronous dosing of aspirin was necessary, aspirin's potentiating effects appear to be produced by mechanism(s) unrelated to its potent, irreversible inhibition of platelet cyclooxygenase.

Prostacyclin production by rat aorta "in vitro" is increased by the combined action of dipyridamole plus pentoxifylline

The present study evaluates the effect of dipyridamole and pentoxifylline, individually and in combination, on PGI2-like production and arachidonic acid metabolism of rat aorta "in vitro". Pentoxifylline 100 microM and dipyridamole 92 and 184 microM increased PGI2-like activity, as measured by the platelet aggregation inhibitory capacity of the aortic ring incubates, by 71%, 46% and 60% respectively; a greater increase in PGI2-like activity was observed with the combination of the drugs than when they were used separately. This effect was observed even at the lowest doses assayed. In fact, dipyridamole 9.2 microM plus pentoxifylline 1 microM increased the PGI2-like activity by 30% while the individual increase was 4.5% and 10.6% respectively. To obtain more information on the effect of the dipyridamole-pentoxifylline combination on arachidonic acid metabolism, arteries were incubated with (1-14C) arachidonic acid, and the 6-keto-PGF1 alpha and PGE2 quantified. Dipyridamole 92 microM plus pentoxifylline 1 and 10 microM increased 6-keto-PGF1 alpha and PGE2 production by about 30% and 48% respectively while the combination with pentoxifylline 100 microM increased the 6-keto-PGF1 alpha 76.5% and the PGE2 50%. The possible biological effect and therapeutic implications of increased PGI2 production by the arteries due to the dipyridamole-pentoxifylline combination remains to be ascertained.

Pharmacokinetics of sulphinpyrazone and its major metabolites after a single dose and during chronic treatment

The pharmacokinetics of sulphinpyrazone and its major metabolites (sulfide, sulfone, p-hydroxysulfone and p-hydroxy-sulphinpyrazone) were investigated in 9 volunteers after a single oral dose as well as after chronic treatment for 23 days. Chronic administration of sulphinpyrazone, in comparison with a single oral dose, led to significant changes in plasma AUC (115.86 to 42.90 mg/l . h), in renal clearance (1.06 to 1.80 l/h), in hepatic intrinsic clearance (319.0 to 598.0 l/h), and in the unbound fraction in plasma 1.15 to 1.69%) and in tissue (2.73 to 1.31%). The volume of distribution changed from 20.24 to 52.04 l. The steady state concentrations predicted from the single dose were significantly higher than the values found after chronic treatment. The results suggest that sulphinpyrazone induces its own metabolism. The metabolism of the sulfone, p-hydroxysulfone and the p-hydroxy-sulphinpyrazone to further degradation products was also induced. Chronic treatment with sulphinpyrazone reduced the plasma AUC of the sulfide and caused a decrease in its elimination half-life (20.9 to 14.3 h). Since considerable amounts of the sulfide are formed in the G.I. tract, it is suggested that besides the induction of metabolism, bacteria which reduce sulphinpyrazone to the sulfide may also be responsible for the observed pharmacokinetic changes.

The effect of oral administration of dipyrone on the capacity of blood platelets to synthesize thromboxane A2 in man

Platelet aggregation and thromboxane A2 (TXA2) production induced by arachidonic acid and collagen were studied in 10 healthy volunteers prior to and at various times after the oral administration of a single dose of 1 g dipyrone. The plasma concentrations of four dipyrone metabolites were also determined. Dipyrone inhibited platelet aggregation and markedly decreased TXA2 synthesis induced by threshold concentrations of both agonists. Maximal inhibition was noted 1 hour after drug administration and in some subjects it lasted as long as 72 h. At all times the effect of the drug could be abolished by increasing the concentration of the agonist. This is consistant with a competitive inhibitory effect of dipyrone on prostaglandin synthetase activity. The mean plasma concentration of the main dipyrone metabolite methylaminoantipyrine at 1 h was 11 micrograms/ml. There was no correlation between individual plasma levels and the parameters of platelet function. At 24h the mean concentration of each of the metabolites studied was up to 1 microgram/ml, and these levels, too, did not correlate with the biological effect of the drug.

Thrombosis: the relationship of hemostatic mechanisms to drug therapy

The mechanism of action and present clinical role of drugs affecting hemostasis in the therapy of spontaneous, postoperative, and posttraumatic arterial thrombosis, arterial embolism, venous thrombosis, pulmonary embolism, and intracranial aneurysm have been reviewed. Both the management of neurosurgical problems and the development of antithrombotic regimens are improving. In regard to the use of drug therapy, discussed herein, each surgeon will reach his own decision based on his findings in the individual patient, and may wisely elect in specific situations not to employ drug therapy. The comments offered in ths analysis are to be construed as suggestions not mandates, as they will undoubtedly undergo modification with time. In closing, it is appropriate to recall a famous Chinese curse: "May you live," it reads, "in a time of transition."

Trial of dipyridamole-aspirin in recurring venous thrombosis

38 patients (26 men) with recurring venous thromboembolism (RVTE) were enrolled in a prospective double-blind, placebo-controlled trial of dipyridamole (DPY), 100 mg a day, and aspirin (ASA), 1200 mg a day. Platelet survival (51Cr labelling of autologous platelets) was measured every 6 months for 18 months. 19 patients were randomised to treatment with DPY and ASA, and 1 had new venous thrombosis (after 15 months of treatment); 19 received placebo and 7 had new venous thrombosis (4--16 months later (chi 2 = 5.70; p< 0.05). DPY-ASA increased platelet survival whereas placebo treatment did not. The results suggest that in patients with RVTE and abnormal platelet survival time DPY in combination with ASA decreases the frequency of new venous thrombosis. Peptic ulcers developed in 2 patients treated with DPY-ASA.

Insulin requirements in diabetic patients treated with sulphinpyrazone

Forty-one adult diabetic patients of either sex who had been controlled by insulin alone for at least one year were randomly allocated in a double-blind, between-patient study, to either sulphinpyrazone (600--800 mg daily) or an identnd at the end of it, no clinically or statistically significant change of the insulin needs of the patients was observed. It is concluded that no clinical interaction occurs between sulphinpyrazone (800 mg/day or 600 mg/day) and insulin when they are administered simultaneously for long periods. In the doses used the tolerability of sulphinpyrazone was very good.