Omalizumab

Omalizumab is a monoclonal antibody that binds to immunoglobulin E (IgE). It is used as additional therapy in individuals with proven IgE-mediated sensitivity to inhaled allergens, whose severe persistent allergic asthma cannot be controlled adequately with high-dose inhaled corticosteroid together with a long-acting beta₂ agonist. Omalizumab should be initiated by physicians in specialist centres experienced in the treatment of severe persistent asthma.

Churg-Strauss syndrome has occurred rarely in patients given omalizumab; the reaction is usually associated with the reduction of oral corticosteroid therapy. Churg-Strauss syndrome can present as eosinophilia, vasculitic rash, cardiac complications, worsening pulmonary symptoms, or peripheral neuropathy. Hypersensitivity reactions can also occur immediately following treatment with omalizumab or sometimes more than 24 hours after the first injection.

For details on the management of anaphylaxis, see section 3.4.3.

The Scottish Medicines Consortium has advised (May 2011) that omalizumab is accepted for restricted use within NHS Scotland as add-on therapy to improve asthma control in children (6 to 12 years), adolescents, and adults with severe persistent allergic asthma. Omalizumab is restricted to patients who are prescribed chronic systemic corticosteroids and in whom all other treatments have failed. The response should be assessed at 16 weeks and omalizumab treatment discontinued in patients who have not shown a marked improvement in overall asthma control.

Anaphylaxis

Anaphylaxis is a severe, life-threatening, generalised or systemic hypersensitivity reaction. It is characterised by the rapid onset of respiratory and/or circulatory problems and is usually associated with skin and mucosal changes; prompt treatment is required. Patients with pre-existing asthma, especially poorly controlled asthma, are at particular risk of life-threatening reactions. Insect stings are a recognised risk (in particular wasp and bee stings). Latex and certain foods, including eggs, fish, cow’s milk protein, peanuts, sesame, shellfish, soy, and tree nuts may also precipitate anaphylaxis. Medicinal products particularly associated with anaphylaxis include blood products, vaccines, hyposensitising (allergen) preparations, antibacterials, aspirin and other NSAIDs, and neuromuscular blocking drugs. In the case of drugs, anaphylaxis is more likely after parenteral administration; resuscitation facilities must always be available for injections associated with special risk. Anaphylactic reactions may also be associated with additives and excipients in foods and medicines. Refined arachis (peanut) oil, which may be present in some medicinal products, is unlikely to cause an allergic reaction — nevertheless it is wise to check the full formula of preparations which may contain allergens.

First-line treatment of anaphylaxis includes securing the airway, restoration of blood pressure (laying the patient flat and raising the legs, or in the recovery position if unconscious or nauseated and at risk of vomiting) and administration of adrenaline (epinephrine) injection. Adrenaline is given intramuscularly in a dose of 500 micrograms (0.5 mL adrenaline injection 1 in 1000); a dose of 300 micrograms (0.3 mL adrenaline injection 1 in 1000) may be appropriate for immediate self-administration. The dose is repeated if necessary at 5-minute intervals according to blood pressure, pulse, and respiratory function (important: possible need for intravenous route using dilute solution, see below). Patients receiving beta-blockers require special consideration (see under Adrenaline). High-flow oxygen administration (section 3.6) and intravenous fluids (section 9.2.2) are also of primary importance. An antihistamine (e.g. chlorphenamine, given by slow intravenous injection or intramuscular injection in a dose of 10 mg, see under Chlorphenamine) is a useful adjunctive treatment, given after adrenaline. An intravenous corticosteroid e.g. hydrocortisone (preferably as sodium succinate) in a dose of 200 mg (section 6.3.2) is of secondary value in the initial management of anaphylaxis because the onset of action is delayed for several hours, but should be given to prevent further deterioration in severely affected patients.

Continuing respiratory deterioration requires further treatment with bronchodilators including inhaled or intravenous salbutamol (see under Salbutamol), inhaled ipratropium (see under Ipratropium), intravenous aminophylline (see under Aminophylline), or intravenous magnesium sulfate [unlicensed indication] (see Acute Severe Asthma); in addition to oxygen, assisted respiration and possibly emergency tracheotomy may be necessary.

When a patient is so ill that there is doubt about the adequacy of the circulation, the initial injection of adrenaline may need to be given as a dilute solution by the intravenous route; for details of cautions, dose, and strength, see under Intravenous Adrenaline (Epinephrine).

Cardiopulmonary arrest may follow an anaphylactic reaction; resuscitation should be started immediately (see Cardiopulmonary Resuscitation).

For advice on the management of medical emergencies in dental practice, see Prescribing in Dental Practice.

On discharge, patients should be considered for further treatment with an oral antihistamine (section 3.4.1) and an oral corticosteroid (section 6.3.2) for up to 3 days to reduce the risk of further reaction. Patients should be instructed to return to hospital if symptoms recur and to contact their general practitioner for follow-up.

Patients who are suspected of having had an anaphylactic reaction should be referred to a specialist for specific allergy diagnosis. Avoidance of the allergen is the principal treatment; if appropriate, an adrenaline auto-injector should be given or a replacement supplied (see Self-administration of Adrenaline).

Intramuscular adrenaline (epinephrine)

The intramuscular route is the first choice route for the administration of adrenaline (epinephrine) in the management of anaphylaxis. Adrenaline is best given as an intramuscular injection into the anterolateral aspect of the middle third of the thigh; it has a rapid onset of action after intramuscular administration and in the shocked patient its absorption from the intramuscular site is faster and more reliable than from the subcutaneous site.

Patients with severe allergy should be instructed in the self-administration of adrenaline by intramuscular injection (for details see under Self-administration of Adrenaline (Epinephrine), below).

Prompt injection of adrenaline is of paramount importance. The following adrenaline doses are recommended for the emergency treatment of anaphylaxis by appropriately trained healthcare professionals and are based on the revised recommendations of the Working Group of the Resuscitation Council (UK).

Dose of intramuscular injection of adrenaline (epinephrine) for the emergency treatment of anaphylaxis by healthcare professionals
Age	Dose	Volume of adrenaline 1 in 1000 (1 mg/mL)
Child under 6 years	150 micrograms	0.15 mL1
Child 6–12 years	300 micrograms	0.3 mL
Adult and child 12–18 years	500 micrograms	0.5 mL2
These doses may be repeated several times if necessary at 5-minute intervals according to blood pressure, pulse, and respiratory function.

___________

1. Use suitable syringe for measuring small volume

2. 300 micrograms (0.3 mL) if child is small or prepubertal

Intravenous adrenaline (epinephrine)

Intravenous adrenaline should be given only by those experienced in its use, in a setting where patients can be carefully monitored. When the patient is severely ill and there is real doubt about the adequacy of the circulation and absorption after intramuscular injection, adrenaline (epinephrine) can be given by slow intravenous injection in a dose of 50 micrograms (0.5 mL of the dilute 1 in 10 000 adrenaline injection) repeated according to response; if multiple doses are required, adrenaline should be given as a slow intravenous infusion stopping when a response has been obtained; children may respond to as little as 1 microgram/kg (0.01 mL/kg of the dilute 1 in 10 000 adrenaline injection) by slow intravenous injection.

Great vigilance is needed to ensure that the correct strength of adrenaline injection is used; anaphylactic shock kits need to make a very clear distinction between the 1 in 10 000 strength and the 1 in 1000 strength. It is also important that, where intramuscular injection might still succeed, time should not be wasted seeking intravenous access.

For reference to the use of the intravenous route for cardiac resuscitation, see section 2.7.3.

Self-administration of adrenaline (epinephrine)

Individuals at considerable risk of anaphylaxis need to carry adrenaline (epinephrine) at all times and need to be instructed in advance when and how to inject it. In addition, the packs need to be clearly labelled with instructions on how to administer adrenaline (intramuscularly, preferably at the midpoint of the outer thigh, through light clothing if necessary) so that in the case of rapid collapse someone else is able to give it. It is important to ensure individuals at risk and carers understand that:

• 
  

  two injection devices should be carried at all times to treat symptoms until medical assistance is available; if, after the first injection, the individual does not start to feel better, the second injection should be given 5 to 15 minutes after the first,

• 
  

  an ambulance should be called after every administration, even if symptoms improve,

• 
  

  the individual should lie down with their legs raised (unless they have breathing difficulties, in which case they should sit up) and, if possible, should not be left alone.

Adrenaline for administration by intramuscular injection is available in ‘auto-injectors’ (e.g. Emerade^®, EpiPen^®, and Jext^®), pre-assembled syringes fitted with a needle suitable for very rapid administration (if necessary by a bystander or a healthcare provider if it is the only preparation available); injection technique is device specific.

For doses of adrenaline for self-administration, see individual preparations under Adrenaline/Epinephrine (Intramuscular Injection for Self-administration).

     ADRENALINE/EPINEPHRINE

Indications emergency treatment of acute anaphylaxis; angioedema; cardiopulmonary resuscitation (section 2.7.3); priapism [unlicensed] (section 7.4.5)

Cautions for cautions in non-life-threatening situations, see section 2.7.3

Interactions Severe anaphylaxis in patients taking beta-blockers may not respond to adrenaline — consider bronchodilator therapy, see intravenous salbutamol; adrenaline can cause severe hypertension and bradycardia in those taking non-cardioselective beta-blockers. Other interactions, see Appendix 1 (sympathomimetics).

Renal impairment section 2.7.3

Pregnancy section 2.7.3

Breast-feeding section 2.7.3

Side-effects section 2.7.3

Dose

• 
  

  Acute anaphylaxis, by intramuscular injection (preferably midpoint in anterolateral thigh) of 1 in 1000 (1 mg/mL) solution for administration by healthcare professionals, see notes and table above

  
  
• 
  

  Acute anaphylaxis, by intramuscular injection for self-administration, see under preparations

  
  
• 
  

  Acute anaphylaxis when there is doubt as to the adequacy of the circulation, by slow intravenous injection of 1 in 10 000 (100 micrograms/mL) solution (extreme caution — specialist use only), see notes above

  
  
  
  

  Important Intravenous route should be used with extreme care by specialists only, see notes above

   Intramuscular or subcutaneous

⁵⁴Adrenaline/Epinephrine 1 in 1000 (Non-proprietary)

Injection, adrenaline (as acid tartrate) 1 mg/mL, net price 0.5-mL amp = £5.06; 1-mL amp = 41p

Excipients may include sulfites

⁵⁵Minijet^® Adrenaline 1 in 1000 (UCB Pharma)

Injection, adrenaline (as hydrochloride) 1 in 1000 (1 mg/mL), net price 1 mL (with 25 gauge × 0.25 inch needle for subcutaneous injection) = £13.90, 1 mL (with 21 gauge × 1.5 inch needle for intramuscular injection) = £15.00 (both disposable syringes)

Excipients include sulfites

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