An investigation of the effect on platelet function of acetylsalicylic acid, dipyridamole and the two drugs in combination in patients with transient attacks of ischaemia.

Twenty patients suffering from transient attacks of ischaemia were studied. Seven received acetylsalicylic acid, six dipyridamole and seven a combination of the two drugs. No significant difference in platelet aggregation was shown in the acute phase between the three treatment groups using an adenosine diphosphate test method. Using Thrombofax platelet substitute, however, a significant difference was seen in all measures. On the seventh day following the ischaemic attack the Thrombofax values returned to normal but, in contrast, Platelet Factor 4 release was increased. Monthly testing of platelet activity during treatment shows that the combination of acetylsalicylic acid with dipyridamole was more effective in bringing about an early inhibition of Platelet Factor 4 release than either agent alone.