Aspirin coagulation disorders

As discussed previously, aspirin inhibits platelet-induced thrombus formation through its ability to inhibit thromboxane biosynthesis. Aspirin has therefore been used to help prevent the onset or recurrence of heart attacks in some individuals by inhibiting thrombus formation in the coronary arteries.97,109 Similarly, daily aspirin use may help prevent transient ischemic attacks and stroke by preventing cerebral infarction in certain patients.97,109 The role of aspirin in treating coagulation disorders is discussed in more detail in Chapter 25... 

Single low doses of aspirin (81 mg daily) produce a slightly prolonged bleeding time, which doubles if administration is continued for a week (see Chapter 34 Drugs Used in Disorders of Coagulation). The change is due to irreversible inhibition of platelet COX, so that aspirin s antiplatelet effect lasts 8-10 days (the life of the platelet). 

Diclofenac is contraindicated in those with a history of hypersensitivity to aspirin or another NSAID, severe heart failure, patients with previous or active peptic ulceration, or porphyria. It should be avoided in pregnancy. It should be used with caution in patients with allergic disorders, renal, hepatic and cardiac impairment, the elderly, in lactation and in those with coagulation defects. 

Dr. David Calverley is a hematologist with a research interest in the molecular mechanisms of platelet adhesion and activation. His clinical interest lies in the area ofplatelet and hemostatic disorders. In addition to research, clinical, and teaching activities, he is Associate Director of the University of Southern Califomia/Nonis Cancer Hospital Qinical Coagulation Laboratoiy. Dr. Gerald Roth is a hematologist with interests in both research and clinical aspects of platelets. He has studied molecular aspects of aspirin s effect on platelets and observed the acetylation reaction between aspirin and platelet cyclo-oxygenase. 

As a general precaution, ginkgo biloba may increase the risk of excessive bleeding, especially for people with blood circulation disorders and for those taking ibuprofen, aspirin, or other anti-coagulants. 

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