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INTRODUCTION

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  • The clinical manifestations of bleeding disorders are usually mild but may be severe if there is an accompanying hemostatic abnormality or a local lesion that may be predisposed to bleed.

  • The usual laboratory abnormalities are prolongation of the bleeding time and/or abnormal platelet aggregation, but these results do not necessarily predict the risk of clinical bleeding.

  • Table 77–1 lists the principal causes of acquired qualitative platelet abnormalities.

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TABLE 77–1ACQUIRED QUALITATIVE PLATELET DISORDERS
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DRUGS THAT AFFECT PLATELET FUNCTION

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  • Table 77–2 lists drugs known to interfere with platelet function. Drugs are the most common cause of abnormal platelet function.

  • Some drugs can prolong the bleeding time and cause or exacerbate a bleeding disorder.

  • Some drugs prolong the bleeding time or induce abnormal platelet function tests but do not cause bleeding.

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TABLE 77–2DRUGS THAT INHIBIT PLATELET FUNCTION
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Aspirin

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  • Two isoforms of cyclooxygenase have been identified (COX-1 and COX-2). COX-1 is constitutively expressed by many tissues, including platelets, the gastric mucosa, and endothelial cells. COX-2 is undetectable in most tissues, but its synthesis is rapidly induced in cells such as endothelial ...

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