Plasma transfusion, specifically fresh frozen plasma (FFP), can be used as an alternative treatment for acute hereditary angioedema attacks when specific C1 esterase inhibitor (C1-INH) products (like Berinert, Ruconest, or Cinryze) are not available.

FFP contains C1-INH and other complement proteins, which help restore the deficient enzyme and reduce bradykinin production, thereby decreasing swelling. It is given by intravenous infusion and can be life-saving in emergencies, especially for airway involvement. However, it may worsen symptoms temporarily in some cases because it also contains complement components that can activate inflammation before C1-INH levels rise.

FFP is generally considered a backup option rather than first-line therapy, used in resource-limited settings or when C1-INH–specific treatments are unavailable.