22 children and 39 adults, were treated for a total of 468 acute attacks, which included 230 abdominal attacks and 133 cases of laryngeal edema. C1-INH successfully treated the symptoms in all of the patients; for most, 500 U were required; however, 9 patients required an additional 500 U to achieve symptom control. Eight of these 9 were due to laryngeal edema triggered by an airway infection. The group also examined a subset of the patients to determine average time between receiving C1-INH and the ﬁrst signs of clini- cal improvement. On average, laryngeal edema symptoms started to improve within 15 minutes of receiving C1-INH, while abdominal symptoms started to improve within 30 minutes. The improvement in subcutaneous edema usually took longer than 30 minutes. Patients were also followed for adverse reactions or hepatitis B, hepatitis C, or HIV trans- mission, and none of the 61 patients had any severe adverse effects or viral transmission after C1-INH therapy. A poster presentation from the 2007 ACAAI meeting presented a randomized, double-blind, placebo-controlled trial with 68 subjects receiving nanoﬁltered C1-INH versus placebo for the treatment of acute HAE attacks involving the abdomen, face, or genitourinary area. They demonstrated signiﬁcantly shorter time from treatment infusion to “begin- ning of unequivocal relief” in the C1-INH treatment group (n = 35; median time = 2 hours) versus placebo group (n = 33; median time 4 hours) (Zuraw et al 2007). At the 2008 AAAAI Meeting, 3 abstract presentations reported some of the most recent trials with C1-INH concen- trate. The IMPACT 1 (International Multicenter Prospective Angioedema C1-INH Trials) involved 125 HAE patients randomly assigned to receive 1 of 3 different treatments for acute HAE attacks (Bernstein et al 2008): placebo; 10 U/kg of C1-INH; 20 U/kg of C1-INH. The time from the treatment infusion to the beginning of improvement was signiﬁcantly shorter in the group treated with 20 U/kg of C1-INH (median time 30 minutes) versus placebo (median time 90 minutes). However, the group treated with the 10 U/kg C1-INH infu- sion was not signiﬁcantly shorter (median time 70 minutes). There was no reported viral seroconversion after C1-INH administration. Only minor side effects were reported which were actually more common in the placebo group. The IMPACT 2 is an open-label North American study in which 39 subjects were treated for 355 episodes of HAE acute attacks with 20 U/kg of C1-INH (Craig et al 2008). Median time to the beginning of symptom relief after administration of the C1-INH was 30 minutes – the same as that in the IMPACT 1 Trial. The time from infu- sion to the beginning of relief of symptoms was similar Therapeutics and Clinical Risk Management 2008:4(5) Plasma-derived C1 inhibitor for hereditary angioedema in all types of HAE attacks: for laryngeal attacks median time was 25 minutes; for abdominal attacks the median time was 26 minutes; for both peripheral and facial attacks median time was 32 minutes. There were no conﬁrmed viral seroconversions during this study. Another poster presentation, from the 2008 AAAAI meeting, demonstrated the use of C1-INH as a prophylactic treatment. Twenty-two patients were involved in a 24-week cross-over study receiving C1-INH 1000 U twice weekly for 12 weeks and placebo (normal saline) treatment for 12 weeks. The subjects had fewer attacks during the C1-INH treatment period than the placebo period (mean 6.1 versus 12.7, p 0.0001) (Zuraw et al 2008). Because some patients with HAE are subject to frequent attacks, several groups have examined C1-INH concentrate infusions at home so patients do not have to obtain urgent care each time they have an attack (Levi et al 2006; Longhurst et al 2007). This includes Levi et al who assessed the option of self-administration of C1-inhibitor concentrate in patients with HAE as well as patients with acquired angioedema. In their study, patients were taught to establish intravenous access and infuse C1-INH at home. They enrolled only patients with frequent attacks for two different studies: one group of 12 patients received C1-INH regularly to pre- vent acute attacks, and the other group of 31 patients had C1-INH available at home “on demand” for the treatment of acute attacks. In the “on demand” group, when the patient administered the C1-INH at home, the time from symptom onset to treatment was reduced compared with those who had to travel to a hospital (1.4 ± 1.0 hours compared to 3.4 ± 2.1 hours). More importantly, the time to complete resolution of symptoms was even more reduced (5.9 ± 2.2 hours versus 13.8 ± 2.9 hours), which is a reﬂection that earlier treatment may be more effective and lead to a more rapid resolution, as seen in other studies (Bork et al 2005). The second study group received C1-INH as a prophylactic treatment at home. At the time of enrollment, patients had exacerbations at least once every 10 days and an average of 4 attacks per month. These patients were then treated with a prophylactic dose of 1000 U of C1-INH approximately every 5–7 days (mean 6.8 days). The patients had a sig- niﬁcant reduction in the number of attacks – 7 of 12 had no angioedema attacks after prophylaxis, 3 of 12 had fewer than 1 attack every 6 months, and 2 of 12 had fewer than 1 attack in 3 months. The overall angioedema attack rate decreased from a mean of 4 attacks per month to 0.3 attacks per month. Patients had no serious reactions. These studies demonstrated that home administration of C1-INH has the 979