ACE inhibitors cause angioedema in up to 1% of patents, but this is not dose dependent. More than half of cases appear during the first few days of treatment, but it can appear at any time, even after years of stable ACEI therapy. Angioedema (rather than allergic reaction) will be suspected if the swelling is localised and there is no itching.^9,19

Those most likely to experience ACEI-related angioedema are the elderly, females, people of African heritage who have previously experienced drug reactions, and people on immunotherapy.¹⁹

Oedema is likely due to vasodilatation causing hypotension from an inflammatory process triggered by kallikrein increasing levels of bradykinin, substance P and other immunomodulatory agents. In addition to stopping ACEI medication, immediate treatment may require intravenous steroids, adrenaline, or antihistamine or emergency treatment if breathing or swallowing is blocked.