The other C1INH is rhucin, still not approved in U.S. This drug is characterized by a short half-life (approximately two to four hours) compared with the plasma-derived C1INH agents (24 to 48 hours). It is contraindicated in patients with rabbit hypersensitivity, as it is purified from rabbit breast milk.10
Ecallantide is a kallikrein inhibitor for acute therapy that is administered via three subcutaneous injections. This agent has been linked to allergic/anaphylactic reactions in a minority of patients (approximately 4%); therefore, it should be administered cautiously, by a health-care provider, and in a setting where anaphylaxis can be successfully managed.12 Icatibant is a bradykinin antagonist recently approved in the U.S. and administered SC via a single injection.10
In light of the development of these new agents, there is a need for updated guidelines for the long- and short-term prophylaxis and acute management of HAE. A recent guideline focused on the management of HAE in gynecologic and obstetric patients recommended the use of plasma-derived C1INH C1 esterase inhibitor (human) (Cinryze) for short- and long-term prophylaxis and acute treatment of HAE.13 The effect of pregnancy on HAE is variable: Some women worsen and other women have less swelling during their pregnancy. Swelling at the time of parturition is rare; however, the risk rises during the post-partum period.
Type III HAE. An additional form of HAE has been recognized with a pattern of AE episodes that mimics Type I or Type II HAE but with unremarkable laboratory studies of the complement cascade, including C1 inhibitor level and function. At this time, there is no laboratory test with which a diagnosis of Type III HAE can be confirmed. The diagnosis should be suspected in patients with a strong family history of AE reflecting autosomal dominant inheritance. In some, but not all, cases, the condition is manifest in association with high estrogen levels (e.g. pregnancy or administration of oral contraceptives). Type III HAE patients have a salutary response to the same agents that are efficacious for Type I and II HAE.
Acquired C1 inhibitor deficiency (ACID). ACID generally occurs in adults and is clinically indistinguishable from HAE. ACID is not associated with a remarkable family history of AE. In contrast to HAE, this is a consumptive deficiency of C1 inhibitor and results from enhanced catabolism that exceeds the capacity for regenerating C1 inhibitor protein. It is often associated with neoplastic (usually lymphoproliferative) or autoimmune disorders; treatment of the underlying condition frequently leads to improvement in ACID. Although its management is similar to HAE, it tends to be more responsive to anti-fibrinolytics. A salutary response to C1INH replacement therapy might not occur in patients with autoantibodies to C1 inhibitor, but efficacy of ecallantide and icatibant for the treatment of acquired AE has been reported.14, 15
ACEI angioedema. Treatment with angiotensin-converting enzyme inhibitors (ACE-I) has been associated with recurrent AE without urticaria in 0.1 to 0.7% of patients exposed to these drugs.16 Angioedema from ACE-I more frequently occurs within the first few months of therapy, but it might occur even after years of continuous therapy. ACEI-induced AE is secondary to impaired degradation of bradykinin. The main treatment is to discontinue the offending agent and avoid all other ACE-I, as this is a class-specific reaction.17
Angiotensin receptor blockers (ARBs) have been associated less commonly with AE. The mechanism for ARB-associated AE has not been elucidated. A meta-analysis showed that in 2% to 17% of patients who were switched to ARBs, recurrence of AE was observed.18 From the pooling of these data with two randomized controlled trials, it is estimated that approximately 10% or less of patients with ACEI-associated AE who switched to ARBs will develop AE.19 In the majority of cases, patients can be switched to ARBs with no recurrence of AE; however, the decision to prescribe an ARB to a patient who has had AE while receiving ACEI should be made carefully on an individualized risk/benefit basis.19