tromboxaner

Thromboxanes are a family of bioactive lipids in the broader prostanoid class, derived from arachidonic acid through the cyclooxygenase (COX) pathway and the action of thromboxane synthase. The most important member is thromboxane A2 (TXA2), which is produced mainly by platelets. TXA2 is unstable and rapidly hydrolyzes to thromboxane B2 (TXB2), a more stable metabolite commonly used as a surrogate marker for TXA2 formation.

TXA2 acts as a potent vasoconstrictor and promoter of platelet aggregation. It is sensed by thromboxane receptors (TP receptors) on platelets and vascular smooth muscle, triggering clot formation and vasoconstriction. Endothelium releases prostacyclin (PGI2), which opposes TXA2 effects; the balance between TXA2 and PGI2 helps regulate hemostasis and blood flow.

Clinical relevance of thromboxanes centers on their role in thrombosis and vascular tone. Pharmacologically, aspirin and other NSAIDs reduce TXA2 production by inhibiting COX-1 in platelets, contributing to antithrombotic effects. Selective COX-2 inhibitors can shift the balance toward TXA2, with potential cardiovascular risk. TXA2 and its metabolites are also measured indirectly through TXB2 or urinary 11-dehydro-TXB2 as markers of platelet activation.

Because of its short half-life and rapid metabolism, TXA2 exerts rapid, short-range actions with systemic effects dependent on the overall thromboxane-prostacyclin balance.