Microvascular permeability and venous tone

Microvascular permeability and venous tone refers to a set of physiological parameters and clinical endpoints rather than a single molecular target such as a receptor or enzyme (Source: PubMed, PMID: 15500339). Microvascular permeability is the capacity of the capillary and post-capillary venule walls to allow the passage of fluids, solutes, and cells, which is often pathologically increased in inflammatory states. Venous tone describes the degree of contraction of the smooth muscle within the venous wall, which is essential for maintaining venous return and preventing blood pooling in the lower extremities (Source: StatPearls, NBK557563). These processes are the primary focus of venoactive drugs, also known as phlebotonics, used to treat chronic venous insufficiency, varicose veins, and hemorrhoids. Drugs like diosmin and hesperidin modulate these parameters by prolonging the effect of noradrenaline on venous smooth muscle and inhibiting the release of inflammatory mediators like prostaglandins and leukotrienes (Source: PubMed, PMID: 11529667). Because this term encompasses broad physiological functions regulated by various receptors and enzymes, it does not represent a single, discrete therapeutic target molecule.

Other names

Capillary permeabilityVenous wall tensionVascular toneVenous capacitance

Venoactive drugs typically act by increasing the sensitivity of venous smooth muscle to noradrenaline, inhibiting the degradation of noradrenaline by catechol-O-methyltransferase (COMT), and reducing the activation and adhesion of leukocytes to the vascular endothelium, thereby decreasing the release of inflammatory mediators that increase permeability (Source: PubMed, PMID: 15500339; StatPearls, NBK557563).