Tips on prescribing EpiPens

17 Mar 08

1 There are important differences in the way different pens are activated. There are two licensed injectable adrenaline devices (IADs), EpiPen and Anapen. Both are autoinjectors available with a single dose of either 0.15mg or 0.3mg of adrenaline for intramuscular injection – 0.15mg ‘junior’ for a body weight of between 15kg and 30kg, and 0.3mg ‘adult’ for body weight of more than 30kg. There are important differences in the way they are activated. Also the EpiPen has a 16mm needle and the Anapen a 9mm needle. Both are designed to inject through all types of clothing. They should be stored at room temperature.

2 Providing good allergen avoidance advice is as important as providing the device. Although there is much discussion about the provision of emergency medication, the main thrust of allergy care is to provide excellent avoidance advice. If this is done well, administration of intramuscular adrenaline is rarely required in practice.

3 Any patient who has experienced symptoms of airway narrowing or cardiovascular compromise during a previous allergic reaction should be given an IAD. Also, food allergic patients who have asthma that requires inhaled steroids may benefit from an IAD. The devices may also be given to patients with nut allergy who have only reacted to previous trace or cutaneous exposure, as their full sensitivity has never been tested. IADs can be prescribed before referral to allergy services. Those who have suffered reactions to insect sting should also be given an IAD.

4 It’s important to know who doesn’t need an IAD. Patients without asthma who have only ever had mild reactions to ingestion of substantial amounts of allergen do not require an IAD. Most children with egg and milk allergy therefore do not need one, as these allergies are usually mild and resolve within two to three years.

5 Most patients should only be prescribed one IAD at a time. Once the diagnosis is made, the majority of patients who receive adrenaline during a ‘field’ reaction require only a single IAD. It is often convenient for school children to have one IAD at home and one at school. In exceptional circumstances it may be justified to provide more than one IAD in each location – for instance if there was a requirement to use more than one during a previous reaction, if the patient has a high BMI or if they are remote from emergency care (such as when they are travelling abroad).

6 Patients might find it useful to get a trainer pen and practise at home. All patients should be trained to use their own IAD by demonstration with dummy trainer pens, which are available from the manufacturers of both the EpiPen and the Anapen.

7 All patients with an IAD should carry oral antihistamines and should use these first during any allergic reaction. The IAD should only be used after the antihistamine has been taken, or if the patient suffers significant respiratory distress or cardiovascular symptoms. Patients should be told to attend A&E if they have used the IAD as they may become ill again when the dose wears off.

8 All patients who have been given an IAD should be referred to an allergy clinic. These patients are at risk of life-threatening reactions. Referral facilitates allergen identification and allows them to be given detailed written and verbal avoidance advice. Patients receive a printed emergency treatment plan, detailing when the IAD should be administered. For children, a copy is passed to the child’s school or nursery, who are also trained in allergen avoidance and use of emergency medication. This comprehensive approach improves patient knowledge and reduces the frequency and severity of accidental reactions. Allergy services will also advise when IADs are no longer required.

9 It’s important patients know what to do when they ‘misfire’ a pen. The most common mistake is to ‘misfire’ an IAD upside-down with the finger or thumb covering the needle aperture with the result that the adrenaline dose is injected into the finger pulp. This causes intense pain and pallor of the finger and carries a risk of digital ischaemia and tissue loss. Tell the patient to run the finger under warm water and observe. If the circulation does not return in a reasonable time, the patient should go to A&E for a subcutaneous injection of phentolamine into the affected area.

10 Demonstration videos are available online. Patients can get advice and support from the Anaphylaxis Campaign or Allergy UK. A training video is available on the Anaphylaxis Campaign site.

Dr Andrew Clark is consultant in paediatric allergy and Dr Shuaib Nasser is consultant in allergy and asthma at Cambridge University Hospitals NHS Foundation Trust

Competing interests None declared

The new edition of the BNF (BNF55) gives updated guidance on the emergency treatment of anaphylaxis. BNF 55 also contains:

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• latest advice on giving folic acid to prevent neural tube defects

• new prescribing guidance for erythropoietins.