Thromboxanes clinical significance

By virtue of its effects on both cyclo-oxygenase isoenzymes, aspirin inhibits platelet thromboxane A2 formation. This effect in the platelet is irreversible and will persist for the lifetime of the platelet (that is up to 10 days), since the platelet cannot synthesize new cyclo-oxygenase. It is of clinical significance that the dose of aspirin necessary to inhibit platelet thromboxane A2 (around 40 mg/day) is much lower than that needed to inactivate the subendothehal prostacychn (PGI2). Hence, platelet aggregation is inhibited, with some associated dilatation of coronary and cerebral arterioles, at doses that do not... 

In a randomised, placebo-controlled study in 24 healthy subjects zileuton 800 mg every 12 hours was given with naproxen 500 mg every 12 hours for 5 days. No clinically significant change was found in the pharmacokinetics of either drug. Naproxen did not affect the inhibitory effect of zileuton on leukotriene B4 levels and similarly zileuton did not affect the inhibitory effect of naproxen on thromboxane B2. The inhibition of the 5-lipoxygenase pathway by zileuton did not appear to worsen the gastrointestinal effects associated with naproxen. No special precautions would seem necessary. ... 

To determine the relevance of in vitro results to clinical setting, Srivastava extended his previous in vitro study (27) to seven healthy female volunteers, who received 5 g of fresh ginger daily for one week. The serum thromboxane activity (thromboxane B2 formation) at baseline was not significantly different compared to that obtained after one week of ginger administration. There were also no evidence of ecchymosis or reports of unusual bleeding episodes (34). 

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