Ecallantide (trade name Kalbitor) is a drug used for the treatment of hereditary angioedema (HAE) and in the prevention of blood loss in cardiothoracic surgery.

[2] On November 27, 2009, ecallantide was approved by the FDA for the treatment of acute attacks of hereditary angioedema for persons over 16 years of age.

Less common, but observed in more than 5% of patients in clinical trials, are respiratory tract infections, fever, vomiting, itching and upper abdominal pain.

Defective or missing C1-inhibitor permits activation of kallikrein, a protease that is responsible for liberating bradykinin from its precursor kininogen.

[8][9] An excess of bradykinin leads to fluid leakage from blood vessels, causing swelling of tissues typical of HAE.