Effect of treatment with an inhibitor of platelet aggregation on the evolution of background retinopathy: 2 years of follow-up

Review: Diabetes as a procoagulant condition

Major known effects of the metabolic derangements of diabetes in haemostasis are induction of platelet-vascular activation by hyperglycaemia, the increase in fibrinogen, modification of fibrin substrate by glucose and hypofibrinolysis related to insulin resistance. The platelet effects are specifically expressed during high shear stress and may be relevant in particular for developing of micro-angiopathy. Hypofibrinolysis, increased fibrinogen and modifications of fibrin may aggravate microthrombosis and organ damage and contribute to precipitation of coronary and cerebral infarction. In addition to specific anti-diabetic medication to reduce the haemostatic effects, specific antiplatelet and profibrinolytic treatments may be relevant for reducing further the morbidity and mortality in diabetics for both micro- and macro-angiopathy.

Effects of triflusal on arteriosclerosis progression assessed with high-resolution arterial ultrasound

In order to evaluate the effect of triflusal (2-acetyloxy-4-trifluoromethyl benzoic acid), an orally active antiplatelet agent, on arteriosclerosis progression, a pilot, parallel, double-dummy, double-blind clinical trial vs acetylsalicylic acid (ASA) was carried out in patients with subclinical atherosclerotic lesions. The trial consisted of a 2-week run-in placebo phase, followed by a 12-month oral treatment with triflusal (600 mg/day) or ASA (300 mg/day). The primary variable was identified in the ultrasonic biopsy (UB) score; the secondary variables were the UB class changes of each arterial site, the rate of progression (ROP), the intima-media thickness (IMT), and the symptoms of arteriosclerosis. Data were evaluated by use of analysis of variance and Chi-square test. Forty-three patients (31 men, 12 women, mean age 62.8 +/- 8.4 SD) were randomized to triflusal (15 men, 6 women, mean age 64.3 +/- 6.7) or to ASA (16 men, 6 women, mean age 61.3 +/- 9.6). The analysis of variance on the UB score showed no difference between treatments: the patients' UB scores remained unchanged with no progression, thus indicating that no patient worsened during treatment. When all arterial sites under evaluation are considered, 86% of the sites in the triflusal group and 85% in the ASA group remained unchanged. No relevant change was recorded in vital signs and routine laboratory tests. Gastric disturbances were reported by two and three patients treated with triflusal and ASA, respectively. In conclusion, triflusal appears as effective as ASA in slowing arteriosclerosis progression.

The pyrimido-pyrimidine derivatives, dipyridamole, mopidamol and RA-642, prevent from retinal vascular defects in experimental diabetes mellitus

We compared the effects of dipyridamole, RA-642, and mopidamol on platelet activity and thromboxane/prostacyclin balance in relation to the degree of retinal vascularization in a model of experimental streptozotocin-induced diabetes in rats. After 3 months, collagen-induced platelet aggregation in whole blood was 25% higher in diabetic animals than in nondiabetics. Dipyridamole inhibited 43% platelet aggregation, mopidamol 39%, and RA-642 36%. Platelet production of thromboxane B2 was 87% higher in untreated diabetic rats. Mopidamol and RA-642 produced a 46% and 41% inhibition of thromboxane B2. Dipyridamole did not inhibited thromboxane B2 synthesis. Aortic production of 6-keto-PGF1 alpha was 43% lower in untreated diabetic animals and showed no change after treatment with either mopidamol or RA-642. In contrast, dipyridamole caused a 90% increase in aortic production of prostacyclin. Computerized analysis of retinal vascularization showed that untreated diabetic rats had a 81% decrease in the area occupied by peroxidase-labelled vessels as compared with nondiabetics. Treatment with dipyridamole, mopidamol, and RA-642 caused 2.5-fold, 2.8-fold and four-fold increases, respectively, in the percentage of retinal surface occupied by peroxidase-labelled vessels. Differences in retinal vascularization between diabetic animals given RA-642 and nondiabetic controls were negligible.

Collaborative overview of randomised trials of antiplatelet therapy--I: Prevention of death, myocardial infarction, and stroke by prolonged antiplatelet therapy in various categories of patients. Antiplatelet Trialists' Collaboration

OBJECTIVE

To determine the effects of "prolonged" antiplatelet therapy (that is, given for one month or more) on "vascular events" (non-fatal myocardial infarctions, non-fatal strokes, or vascular deaths) in various categories of patients.

DESIGN

Overviews of 145 randomised trials of "prolonged" antiplatelet therapy versus control and 29 randomised comparisons between such antiplatelet regimens.

SETTING

Randomised trials that could have been available by March 1990.

SUBJECTS

Trials of antiplatelet therapy versus control included about 70,000 "high risk" patients (that is, with some vascular disease or other condition implying an increased risk of occlusive vascular disease) and 30,000 "low risk" subjects from the general population. Direct comparisons of different antiplatelet regimens involved about 10,000 high risk patients.

RESULTS

In each of four main high risk categories of patients antiplatelet therapy was definitely protective. The percentages of patients suffering a vascular event among those allocated antiplatelet therapy versus appropriately adjusted control percentages (and mean scheduled treatment durations and net absolute benefits) were: (a) among about 20,000 patients with acute myocardial infarction, 10% antiplatelet therapy v 14% control (one month benefit about 40 vascular events avoided per 1000 patients treated (2P < 0.00001)); (b) among about 20,000 patients with a past history of myocardial infarction, 13% antiplatelet therapy v 17% control (two year benefit about 40/1000 (2P < 0.00001)); (c) among about 10,000 patients with a past history of stroke or transient ischaemic attack, 18% antiplatelet therapy v 22% control (three year benefit about 40/1000 (2P < 0.00001)); (d) among about 20,000 patients with some other relevant medical history (unstable angina, stable angina, vascular surgery, angioplasty, atrial fibrillation, valvular disease, peripheral vascular disease, etc), 9% v 14% in 4000 patients with unstable angina (six month benefit about 50/1000 (2P < 0.00001)) and 6% v 8% in 16,000 other high risk patients (one year benefit about 20/1000 (2P < 0.00001)). Reductions in vascular events were about one quarter in each of these four main categories and were separately statistically significant in middle age and old age, in men and women, in hypertensive and normotensive patients, and in diabetic and nondiabetic patients. Taking all high risk patients together showed reductions of about one third in non-fatal myocardial infarction, about one third in non-fatal stroke, and about one third in vascular death (each 2P < 0.00001). There was no evidence that non-vascular deaths were increased, so in each of the four main high risk categories overall mortality was significantly reduced. The most widely tested antiplatelet regimen was "medium dose" (75-325 mg/day) aspirin. Doses throughout this range seemed similarly effective (although in an acute emergency it might be prudent to use an initial dose of 160-325 mg rather than about 75 mg). There was no appreciable evidence that either a higher aspirin dose or any other antiplatelet regimen was more effective than medium dose aspirin in preventing vascular events. The optimal duration of treatment for patients with a past history of myocardial infarction, stroke, or transient ischaemic attack could not be determined directly because most trials lasted only one, two, or three years (average about two years). Nevertheless, there was significant (2P < 0.0001) further benefit between the end of year 1 and the end of year 3, suggesting that longer treatment might well be more effective. Among low risk recipients of "primary prevention" a significant reduction of one third in non-fatal myocardial infarction was, however, accompanied by a non-significant increase in stroke. Furthermore, the absolute reduction in vascular events was much smaller than for high risk patients despite a much longer treatment period (4.4% antiplatelet therapy v 4.8% control; five year