Adrenaline (epinephrine) provides physiological reversal of the immediate symptoms (such as laryngeal oedema, bronchospasm, and hypotension) associated with hypersensitivity reactions such as anaphylaxis and angioedema. See below for full details of adrenaline administration and for adjunctive treatment.

Anaphylaxis

Anaphylactic shock requires prompt energetic treatment of laryngeal oedema, bronchospasm, and hypotension. Atopic individuals are particularly susceptible. Insect bites are a recognised risk (in particular wasp and bee stings). Certain foods, including eggs, fish, cow's milk protein, peanuts, and nuts may also precipitate anaphylaxis. Medicinal products particularly associated with anaphylaxis include blood products, vaccines, hyposensitising (allergen) preparations, antibiotics, aspirin and other NSAIDs, heparin, 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; some oils, such as arachis (peanut) oil, may be contaminated with allergenic proteins from their original source—it is wise to check the full formula of preparations which may contain allergenic fats or oils (including those for topical application, particularly if they are intended for use in the mouth or for application to the nasal mucosa).

First-line treatment includes securing the airway, restoration of blood pressure (laying the patient flat, raising the feet), and administration of adrenaline (epinephrine) injection. This 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]. Oxygen administration is also of primary importance. An antihistamine (e.g. chlorphenamine (chlorpheniramine), given by slow intravenous injection in a dose of 10–20 mg, see under CHLORPHENAMINE) is a useful adjunctive treatment, given after adrenaline injection and continued for 24 to 48 hours to prevent relapse. In patients on non-cardioselective beta-blockers severe anaphylaxis may not respond to adrenaline injection, calling for administration of salbutamol by intravenous injection. Adrenaline may also cause severe hypertension in those receiving beta-blockers.
Continuing deterioration requires further treatment including intravenous fluids.  intravenous aminophylline ( see under AMINOPHYLLINE) or a nebulised beta₂-adrenoceptor stimulant (such as salbutamol or terbutaline, see SALBUTAMOL and TERBUTALINE); in addition to oxygen, assisted respiration and possibly emergency tracheotomy may be necessary.
An intravenous corticosteroid e.g. hydrocortisone (as sodium succinate) in a dose of 100–300 mg  is of secondary value in the initial management of anaphylactic shock because the onset of action is delayed for several hours, but should be given to prevent further deterioration in severely affected patients.
When a patient is so ill that there is doubt as to 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), below.
Some patients with severe allergy to insect stings or foods are encouraged to carry pre-filled adrenaline syringes (e.g. EpiPen®) for self-administration during periods of risk.

Angioedema

Angioedema is dangerous if laryngeal oedema is present. In this circumstance adrenaline (epinephrine) injection and oxygen should be given as described under Anaphylaxis (see above); antihistamines and corticosteroids should also be given (see again above). Tracheal intubation and other measures may be necessary.

The administration of C₁ esterase inhibitor (in fresh frozen plasma or in partially purified form) may terminate acute attacks of hereditary angioedema, but is not practical for long-term prophylaxis.

Intramuscular adrenaline (epinephrine)

The intramuscular route is the first choice route for the administration of adrenaline (epinephrine) in the management of anaphylactic shock. Adrenaline 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 (the intravenous route should be reserved for extreme emergency when there is doubt as to the adequacy of the circulation, for details of cautions, dose and strength see under Intravenous Adrenaline (Epinephrine), below).

Patients with severe allergy should ideally 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 based on the revised recommendations of the Project Team of the Resuscitation Council (UK).

Volume of adrenaline (epinephrine) injection 1 in 1000 (1 mg/mL) for intramuscular injection (or subcutaneous injection but not generally recommended) in anaphylactic shock

Age      Volume of adrenaline 1 in 1000

Under 6 months          0.05 mL
6 months–6 years        0.12 mL
6–12 years                  0.25 mL
Adult and adolescent   0.5 mL

These doses may be repeated if necessary at 5-minute intervals according to blood pressure, pulse and respiratory function (may be repeated several times).

Intravenous adrenaline (epinephrine)
Where the patient is severely ill and there is real doubt about adequacy of the circulation and absorption from the intramuscular injection site, adrenaline (epinephrine) may be given by slow intravenous injection in a dose of 500 micrograms (5 mL of the dilute 1 in 10 000 adrenaline injection) given at a rate of 100 micrograms (1 mL of the dilute 1 in 10 000 adrenaline injection) per minute, stopping when a response has been obtained; children can be given a dose of 10 micrograms/kg (0.1 mL/kg of the dilute 1 in 10 000 adrenaline injection) by slow intravenous injection over several minutes. Great vigilance is needed to ensure that the correct strength 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.