Vorapaxar is a first in class oral inhibitor of the platelet thrombin receptor PAR-1. Its place in therapy is currently uncertain as trials to date have showed modest benefits in reducing ischaemic events, with substantial risks of haemorrhage, especially intracranial haemorrhage.29
Iloprost is a prostacyclin analogue that exerts its effects by promoting vasodilatation and inhibiting ADP-induced platelet aggregation, thereby opposing the effects of thromboxane A2. It may also increase the rate of metabolism of tissue plasminogen activator by the liver, but must be continuously infused.
Cilostazol, like dipyridamole, is a phosphodiesterase inhibitor and so reduces platelet aggregation but also increases arterial vasodilation. Its use is restricted to those with intermittent claudication, in peripheral arterial disease patients.
Established antiplatelet agents are summarised in table 1, while figure 4 illustrates how our knowledge of platelet physiology has enabled us to inhibit its activity.
The British Committee for Standards in Haematology (BCSH) issued recent guidelines on the management of bleeding in patients taking antithrombotic agents.1 Simply stopping the agent may not be sufficient if bleeding is severe, as it may take several days for platelet function to return to normal (see table 2).
Options to stop bleeding range from basic haemostatic measures (pressure, surgical opinion) to platelet transfusion. Decisions regarding stopping/reversing antithrombotic agents have clear implications for thrombotic risk; specialist advice should be sought.
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