Until now, there is neither a cure for patients who suffer from HAE attacks nor a therapeutic concept to prevent these attacks completely.
Furthermore, in many countries there are currently no acute attack treatments available for HAE patients. Here physicians are therefore limited to providing patients with a short and long term prophylactic treatment with attenuated androgens (such as Danazol and Oxandrolone) and in some cases tranexamic acid (such as Cyklokapron).
Unlike allergic angioedema, HAE attacks do not respond to treatment with anti-histamines, corticosteroids or epinephrine. Current HAE treatment options focus on providing rapid relief during attacks or on the prevention of symptoms in patients who experience a high frequency of attacks or who undergo dental or surgical procedures, which may trigger an attack.
The aim of acute treatment is to halt the progression of the edema and alleviate the symptoms. This applies particularly to episodes affecting the larynx, which can cause death by suffocation if left untreated.
The recommended options for acute treatment vary from country to country due to the fact that drugs for specific treatment are not licensed in all countries. In these cases acute treatment may be limited to more unspecific drugs such as tranexamic acid or even just painkillers.
In countries where it is available, C1-INH concentrate, Icatibant or Ecallantide can be used for the treatment of acute attacks. Icatibant and Ecallantide must be administered by subcutaneous injection by a healthcare professional; C1-INH concentrate must be administered intravenously.
Long-term prophylaxis is given to patients whose quality of life is clearly reduced by HAE. These are usually patients who have either very frequent or very painful attacks or are at high risk of developing laryngeal edema.
Long-term prophylaxis consists mainly of attenuated androgens, synthetically produced derivatives of the male sex hormone testosterone. They can reduce the number of attacks, but as these medications are associated with a range of severe side effects, attenuated androgens are generally reserved for patients suffering from frequent and/or severe symptoms.
In some countries, antifibrinolytic drugs such as tranexamic acid or aminocaproic acid are used as alternative to androgens.
Short-term preventative therapy is recommended for patients undergoing dental procedures or surgery, which have been known to trigger an attack. One option for short-term prophylaxis consists of high dose androgen therapy for at least five days prior to surgery and four days afterwards. Where available, another option is to administer C1-INH concentrate one to two hours prior to surgery.
Treatment of Acute Attacks
Angioedema seen in HAE does not respond to the drugs employed in treating other forms of urticaria/angioedema such as antihistamines, epinephrine and corticosteroids. While epinephrine, in particular, may have a transient effect on swelling, it does not alter the course of an attack.
Maintaining airway patency is the primary concern for patients with laryngeal edema. If the airway is threatened, an experienced physician should intubate the patient. In addition, the capability for emergency tracheotomy should be readily available. Because gastrointestinal edema usually involves excruciating pain, frequent vomiting and the potential for hypotension, therapy should include aggressive fluid replacement and pain management. Clinicians report that Zofran, Compazine and Phenergan are effective in reducing nausea and vomiting, while morphine or other narcotics are routinely used to relieve attack related abdominal pain. Some physicians use fresh frozen plasma in the acute attack setting, but this therapy is considered controversial because in addition to C1-inhibitor, fresh frozen plasma contains substrates of the complement and kinin systems that could produce a vasoactive peptide and cause an attack exacerbation.