Bradykinin is a peptide-based hormone that is formed locally in tissues, very often in response to a trauma. It increases vessel permeability, dilates blood vessels and causes smooth muscle cells to contract. Bradykinin plays an important role in the mediation of pain. Surplus bradykinin is responsible for the typical symptoms of inflammation, such as swelling, redness, overheating and pain. These symptoms are mediated by activation of bradykinin B2 receptors. In patients with HAE, they have an absent or dysfunctional C1-esterase inhibitor. This inhibitor is responsible for the production of bradykinin in which displacement of bradykinin from B2 receptors by icatibant has an inhibitory effect on the receptor for a relatively long time.
Icatibant is a potent, specific, competitive, and selective peptidomimetic bradykinin beta2-receptor antagonist (pA2 = 9.04). It has a modified peptide structure, and is the first bradykinin receptor antagonist to act on the guinea-pig trachea without demonstrating agonist effects. It also inhibits aminopeptidase N (Ki = 9.1 μM). If an IV dose of 0.4 and 0.8 mg/kg was infused over 4 hours, one may observe an inhibited response to bradykinin challenge for 6 - 8 hours following completion of infusion.
Icatibant is metabolized by proteolytic enzymes into inactive metabolites. The cytochrome P450 enzyme system is not involved with the metabolism of icatibant.