title: Treatment of hereditary angioedema with a vapor-heated C1 inhibitor concentrate.
abstract: BACKGROUND
  Hereditary angioedema results from a congenital deficiency of functional C1 inhibitor and is characterized by episodic bouts of edema, which may be life-threatening when they involve the larynx. We evaluated the effectiveness of a C1 inhibitor concentrate in the prevention and treatment of attacks of hereditary angioedema. The concentrate was vapor-heated to inactivate hepatitis and human immunodeficiency viruses.
  
  
  METHODS
  We conducted two double-blind, placebo-controlled studies. The first was a crossover study consisting of two 17-day trials in which prophylactic infusions of either C1 inhibitor (25 plasma units per kilogram of body weight) or placebo were given intravenously every third day to six patients with hereditary angioedema. The second study was conducted in patients with acute attacks of hereditary angioedema and assessed the length of time to a clinical response after infusions of either 25 plasma units of C1 inhibitor per kilogram (55 infusions in 11 patients) or placebo (49 infusions in 11 patients).
  
  
  RESULTS
  The infusions of C1 inhibitor concentrate resulted in close to normal functional levels of C1 inhibitor and C4. As compared with placebo, prophylactic infusions of C1 inhibitor resulted in significantly lower daily symptom scores for the severity of edema of the extremities (P<0.01), larynx (P<0.05), abdomen (P<0.05), and genitourinary tract (P<0.05). Likewise, during the treatment study the time from the start of an infusion to the beginning of improvement in symptoms was shorter for the C1 inhibitor infusions than the placebo infusions (55 vs. 563 minutes, P<0.001). There was no evidence of toxicity.
  
  
  CONCLUSIONS
  Infusions of a vapor-heated C1 inhibitor concentrate are a safe and effective means of both preventing attacks of hereditary angioedema and treating acute attacks.
authors.affiliation: Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Md, USA.
authors.forename: A T
authors.initials: AT
authors.lastname: Waytes
authors.forename: F S
authors.initials: FS
authors.lastname: Rosen
authors.forename: M M
authors.initials: MM
authors.lastname: Frank
mesh_terms: D000799:Angioedema / Q000235:genetics / Q000517:prevention & control / Q000628:therapy*; D003174:Complement C1 Inactivator Proteins / Q000627:therapeutic use*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D006358:Hot Temperature; D006801:Humans; D013242:Sterilization; D016896:Treatment Outcome
chemical_list: D003174:Complement C1 Inactivator Proteins