Aspirin antiplatelet effect

Many dietary supplements have antiplatelet activity, which may increase the risk of bleeding when used concurrently with anticoagulants. Feverfew inhibits cyclooxygenase and phospholipase A2 and may interact with anticoagulants and potentiate the antiplatelet effect of aspirin. Other supplements that possess antiplatelet activity include but are not limited to garlic, ginkgo, vitamin E, vitamin A, and selenium. 

Low-dose aspirin is associated with a reduced risk of major bleeding, particularly GI bleeding. Other GI disturbances (e.g., dyspepsia, nausea) are infrequent with low-dose aspirin. Ibuprofen should not be administered on a regular basis concurrently with aspirin because it may block aspirin s antiplatelet effects. 

All antiplatelet drugs increase the risk of bleeding. Even at the low ASA doses used to inhibit platelet function (100 mg/d), ulcerogenic and bronchocon-strictor (aspirin asthma) effects may occur. Ticlopidine frequently causes diarrhea and, more rarely, leukopenia, necessitating cessation of treatment Clopidogrel reportedly does not cause hematological problems. 

Pharmacology Antithrombotic action is the result of the additive antiplatelet effects of dipyridamole and aspirin. 

Aspirin and ticlopidine are used for their antiplatelet effect. They lower the risk of vascular recurrence by 27%. Asasantine (aspirin 50 mg - - dipyridamole 400 mg) lowers the risk by 37% (ESPS2). Clopidro-gel (75 mg) lowers the risk of recurrent vascular events after cerebral, cardiac or lower limb infarction by 8.7%. 

A. Coumadin, taken in conjunction with ginkgo, could increase the risk of bleeding. Ginkgo has an antiplatelet effect, which has produced bleeding complications in this clinical setting. The other medications Usted are not known to have this problem. Acetaminophen, unlike aspirin, does not have an antiplatelet effect. 

Aspirin irreversibly inhibits platelet COX so that aspirin s antiplatelet effect lasts 8-10 days (the life of the platelet). In other tissues, synthesis of new COX replaces the inactivated enzyme so that ordinary doses have a duration of action of 6-12 hours. 

Because of reported antiplatelet effects, patients using anticlotting medications (eg, warfarin, aspirin, ibuprofen) should use garlic cautiously. Additional monitoring of blood pressure and signs and symptoms of bleeding is warranted. Garlic may reduce the bioavailability of saquinavir, an antiviral protease inhibitor, but it does not appear to affect the bioavailability of ritonavir. 

Aspirin has been in clinical use for more than one hundred years. The antiplatelet effect of this agent was recognized some forty years ago. Since then aspirin has been a life-saving drug for several types of thrombotic indications. Several... 

Catella-Lawson F Reilly MR Kapoor SC, et al. Cyclooxygenase inhibitors and the antiplatelet effects of aspirin. N Engl J Med 2001 345 1809-1817. 

De Caterina R, Giannessi D, Boem A, et al. Equal antiplatelet effects of aspirin 50 or 324mg/day in patients after acute myocardial infarction. Thromb Haemost 1985 54 528-532. 

Lepantalo A, Virtanen KS, Heikkila J, Wartiovaara U, Lassila R, Limited early antiplatelet effect of 300 mg clopidogrel in patients with aspirin therapy undergoing percutaneous coronary interventions, Eur HeartJ 2004 25 476-483. 

Rupprecht HJ, Darius H, Borkowski U, et al, Comparison of antiplatelet effects of aspirin, ticlopidine, or their combination after stent implantation. Circulation 1998 97(1 I) 1046-1052. 

The irreversible inactivation of endogenous enzymes caused by drugs, e.g., the antiplatelet effect of aspirin after oral administration [442], the 5o-reductase inhibition by a new nonsteroidal inhibitor [443], and the H+, K+-ATPase inactivation by proton pump inhibitors [444], is modeled with turnover models. The simplest model [442] includes terms for the production rate kt and loss rate ka of the response E, coupled with a function g (c) representing the change of plasma or effect-compartment drug concentration ... 

Yamamoto, K., Abe, M., Katashima, M., Yamada, Y., Sawada, Y., and Iga, T., Pharmacodynamic analysis of antiplatelet effect of aspirin in the literature. Modeling based on inhibition of cyclooxygenase in the platelet and the vessel wall endothelium, Japan Journal of Hospital Pharmacy, Vol. 22, 1996, pp. 133-141. 

Aspirin inhibits cyclooxygenase, thus impairing platelet aggregation, This may be additive to other drugs with a similar effect and to those which affect other aspects of blood clotting. The risk of interactions and adverse effects is reduced by using a lower dose (e.g. 75mg) fortunately, a full antiplatelet effect is seen at this dose,... 

ASPIRIN ANALGESICS - NSAIDs 1. Risk of gastrointestinal bleeding when aspirin, even a low dose, is co-administered with NSAIDs 2. Ibuprofen 1 antiplatelet effect of aspirin 1. Additive effect 2. Ibuprofen competitively inhibits binding of aspirin to platelets 1. Avoid co-administration 2. Avoid co-administration... 

ASPIRIN ANTIPLATELET AGENTS Risk of bleeding when aspirin is co administered with other antiplatelet agents. The addition of dipyridamole to low-dose aspirin does not seem to confer an t risk of bleeding Additive effect Closely monitor effects watch for signs of excess bleeding... 

Pharmacological inhibition of arachidonic acid metabolism by aspirin impairs platelet-platelet interactions but does not affect platelet adhesion (figure 3). The antiplatelet effects of aspirin are evident in blood anticoagulated with citrate [61,62] and less obvious in studies with native (non anticoagulated) blood [63]. 

Overdose. A moderate overdose (plasma salicylate 500-750 mg/1) will cause nausea, vomiting, epigastric discomfort, tinnitus, deafness, sweating, pyrexia, restlessness, tachypnoea and hypokalaemia. A large overdose (plasma salicylate > 750 mg/1) may result in pulmonary oedema, convulsions and coma, with severe dehydration and ketosis. Bleeding is unusual, despite the antiplatelet effect of aspirin. 

Concomitant use of heparin and oral anticoagulants can increase the risk for bleeding due to the antiplatelet effect of aspirin. In addition, use with alcohol can increase the risk of Gl bleeding. / spirin displaces a number of drugs (e.g., tolbutamide, nonsteroidal anti-inflammatory drugs [NSAIDs], methotrexate, phenytoin, and probenecid) from protein binding sites in the blood. Corticosteroid use can reduce serum salicylate levels by increasing the clearance of aspirin. 

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