Intravenous nanofiltered human C1 inhibitor (C1-INH NF) concentrate (Cinryze) is used as a direct replacement of deficient levels of plasma C1 inhibitor in patients with hereditary angioedema (HAE). In the EU, C1-INH NF concentrate 1000U is indicated in the treatment, pre-procedural prevention, and routine prevention of angioedema attacks in adults and adolescents with HAE. Intravenous C1-INH NF concentrate 1000U effectively relieved angioedema attacks in patients with HAE. In a randomized, double-blind trial in pediatric and adult patients, the median time to onset of unequivocal relief from an attack was significantly shorter with C1-INH NF concentrate than with placebo. In an open-label trial, both unequivocal relief and clinical relief were shown in the majority of attacks within 1 and 4 hours of infusion of C1-INH NF concentrate, regardless of the site (i.e. gastrointestinal, cutaneous, laryngeal, or genitourinary) of the defining symptom. When administered prior to a procedure, open-label intravenous C1-INH NF concentrate 1000U reduced the incidence of angioedema attacks during and after a variety of dental, surgical, or interventional diagnostic procedures in pediatric and adult patients with HAE. Routine preventative treatment with intravenous C1-INH NF concentrate 1000U every 3 or 4 days reduced the number of angioedema attacks. In a randomized, double-blind, crossover trial in pediatric and adult patients with HAE, the mean normalized number of attacks per 12-week period was significantly lower during routine prevention with C1-INH NF concentrate than with placebo. Routine prevention with C1-INH NF concentrate reduced the median monthly attack rate from baseline in an open-label trial. Intravenous C1-INH NF concentrate was well tolerated in clinical trials in patients with HAE. No cases of viral transmission were reported.