Effect of a pyrimidopyrimidine derivative on thrombus formation in the rabbit

Dipyridamole and aspirin tested against an experimental model of thrombosis

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The effect of dipyridamole on tissue perfusion following freezing injury in the rat

A drug with known platelet disaggregating properties, dipyridamole, has been used for the treatment of experimental frost-bite in the rat. A standardized cold injury applied to the rat tail was treated by a variety of régimes. Tissue survival was then assessed by several methods and correlated with the therapeutic régimes. The results suggested that dipyridamole had a beneficial effect on the maintenance of tissue perfusion and subsequent viability of the injured tail.

Altered platelet function in patients with prosthetic mitral valves. Effects of sulfinpyrazone therapy

Platelet survival time and platelet adhesiveness and aggregation were examined in 16 patients with prosthetic mitral valves. Subsequently, nine patients were treated with sulfinpyrazone in doses of 400 mg and 800 mg/day, and the studies were repeated after a treatment period of 5 to 8 weeks. 51 Chromium survival time was shortened in 15 of 16 patients, and the mean value for the entire group was 5.49 ± 0.23 days (normal, 6.73 ± 0.21 days; P < 0.001). Mean platelet adhesiveness in glass bead columns was 53 ± 5% (normal, 30 to 60%). Platelet aggregation (turbidometric technic of Born) was normal. Treatment with 400 mg of sulfinpyrazone daily reduced platelet adhesiveness to 40 ± 5% ( P < 0.05), but effected no change in platelet survival time or platelet aggregation. Therapy with 800 mg of sulfinpyrazone daily corrected platelet survival time to normal, 6.68 ± 0.57 days ( P < 0.01), but it produced no further decrease in adhesiveness and no change in aggregation. It is concluded that platelet abnormalities regularly occur in patients with prosthetic mitral valves and may contribute to thromboembolism in this group. Platelet survival time is a more sensitive measure of altered platelet kinetics than platelet adhesiveness or platelet aggregation. Therapy with 800 mg of sulfinpyrazone per day corrects demonstrated abnormalities and may be useful for prevention of thromboembolism in patients with prosthetic mitral valves.

Effect of RA233 on platelet function in vitro

RA233, a new pyrimido-pyrimidine compound, is a powerful inhibitor of platelet function tested in vitro; it inhibits calcium and adenosine diphosphate (A.D.P.)-induced platelet aggregation, inhibits the retention of platelets by glass beads, decreases the release of platelet factor 3 by kaolin, and inhibits clot retraction. In some in-vitro systems RA233 is significantly more potent that its analogue RA433 in inhibiting platelet function.

Action of a pyrimido-pyrimidine compound on platelet behaviour in vitro

A pyrimido-pyrimidine compound (RA433) was found in vitro to be a significantly more potent inhibitor of platelet behaviour than the previously available pyrimido-pyrimidine compound RA8-dipyridamole. In a turbidimetric system RA433 inhibits platelet aggregation induced by adenosine diphosphate, collagen, and noradrenaline; further, in a glass-bead-column technique it is a powerful inhiitor of platelet adhesiveness.

Controlled trial of dipyridamole in cerebral vascular disease

A controlled double-blind study of the effect of dipyridamole was performed in 169 patients with established cerebral vascular disease. A dose of 400 mg. was used initially, given daily for an average of 14 months; the dose was then increased to 800 mg. daily for a further average period of 11 months. When the incidence of cerebral ischaemic episodes during treatment was compared in the drug-treated and placebo-treated groups no significant difference was found.

The effect on dipyridamole on platelet aggregation and adhesiveness

The effect of dipyridamole (Persantin) on platelet behaviour in human plasma and whole blood has been studied in three experimental systems. Added to plasma and whole blood in a concentration of 50 μg. per ml., dipyridamole inhibited platelet aggregation in a Chandler tube system, and ADP-induced clumping in a turbidimetric system. Adhesiveness of platelets to glass beads in a Hellem system was also decreased by the drug.

Oral administration in doses of 100 mg. 4 times per day suggests a trend in which ADP-induced clumping is lessened after therapy with the drug and one patient is recorded in whom a reduction in platelet adhesiveness to glass beads can probably be attributed to the drug.

The results of this trial coupled with those of previous workers suggest that clinical trials of dipyridamole in human arterial disease are indicated to define the place of this drug in the therapy of arterial disease.

Counteraction of platelet activity at sites of laser-induced endothelial trauma

The effects of dextran 70 (Mw 70,000; Macrodex), heparin, dipyridamole (Persantin), and prostaglandin E(1) on the behaviour of platelets were investigated at sites of endothelial trauma induced with a ruby biolaser in arterioles in the rabbit ear chamber. This technique has several advantages over previous methods of studying platelet activity.Dextran 70 (2 g./kg. body weight) caused a profound reduction in platelet activity four to six hours after its administration. Heparin (12 mg./kg. body weight) had no effect. The effect of dipyridamole (2.5 mg./kg. body weight) was profound immediately after its administration, but was transient. In preliminary experiments single intravenous injections of prostaglandin E(1) (25 and 125 mug./kg. body weight) had no detectable effect.

Dipyridamole: a controlled trial of its effect in acute myocardial infarction

A controlled trial of oral dipyridamole in 103 patients with acute myocardial infarction showed no difference in the number of complications or deaths in either the control or the treated groups. It is concluded that dipyridamole has no benefit in acute myocardial infarction.