Effects of nonsteroidal anti-inflammatory therapy on platelets

Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) can produce a mild, systemic hemostatic defect by inhibiting normal platelet function. Aspirin acetylates and permanently inactivates cyclooxygenase (COX), while nonaspirin NSAIDs reversibly block COX; thus, all of these drugs cause platelet dysfunction by inhibiting the formation of thromboxane A2, a platelet-activating and vasoconstricting eicosanoid. However, spontaneous bleeding complications outside the gastrointestinal tract very rarely result from the use of aspirin and other NSAIDs in individuals who are otherwise hemostatically normal. Most types of surgery are not usually associated with clinically significant bleeding in patients taking these drugs, making it typically unnecessary to discontinue them and thus delay surgery for the purpose of restoring normal hemostasis. Exceptions may include operations at sites where optimal hemostasis is critical, surgical manipulation of the genitourinary tract and oral cavity, and possibly cardiac surgery. Factors that increase the risk of bleeding with aspirin and other NSAIDs include coexisting coagulation abnormalities and the simultaneous use of alcohol or anticoagulants.

Effects of nonsteroidal antiinflammatory drugs on platelet function and systemic hemostasis

Aspirin and nonaspirin nonsteroidal antiinflammatory drugs (NSAIDs) inhibit platelet cyclooxygenase, thereby blocking the formation of thromboxane A2. These drugs produce a systemic bleeding tendency by impairing thromboxane-dependent platelet aggregation and consequently prolonging the bleeding time. Aspirin exerts these effects by irreversibly blocking cyclooxygenase and, therefore, its actions persist for the circulating lifetime of the platelet. Nonaspirin NSAIDs inhibit cyclooxygenase reversibly and, therefore, the duration of their action depends on specific drug dose, serum level, and half-life. The clinical risks of bleeding with aspirin or nonaspirin NSAIDs are enhanced by the concomitant use of alcohol or anticoagulants and by associated conditions, including advanced age, liver disease, and other coexisting coagulopathies.

Comparative pharmacokinetics of coumarin anticoagulants XXV: Warfarin-ibuprofen interaction in rats

The effect of ibuprofen on the pharmacokinetics and anticoagulant action of racemic warfarin was determined in a crossover study on male Sprague-Dawley rats. At average plasma concentrations of 24-83 mg/liter, ibuprofen decreased the biological half-life and increased the total clearance of warfarin. It also increased the anticoagulant effect produced by a given plasma concentration of total (free and protein-bound) warfarin. These effects of ibuprofen appear to be a consequence of its displacing effect on warfarin in plasma.

Interaction study between phenprocoumon and flurbiprofen

The effects of flurbiprofen on various coagulation and haemostasis parameters were studied in 19 patients adequately anticoagulated on a fixed dose of phenprocoumon. Laboratory controls were performed 5 times at weekly intervals. Flurbiprofen 50 mg 3-times daily was given for 2 weeks after an initial control period of 2 weeks. The last control followed 1 week after cessation of flurbiprofen. All changes observed during the administration of flurbiprofen were quantitatively moderate; some reached statistical significance. The prothrombin time (%) Factor II and Factor X values fell; Factor II values remained unchanged. Factor IX values fell only in the first week on flurbiprofen and reached control values thereafter. Phenprocoumon concentration remained constant throughout. There was no change in spontaneous platelet aggregation. Although there was a slight, statistically significant increase in the Ivy bleeding time, it remained within the normal range. These findings suggest that the interference of flurbiprofen with oral anticoagulation is minimal and probably of no clinical relevance.