Medication

Antihistamines

Antihistamines are useful for controlling mild symptoms of allergy.

Cetirizine (known as Benadryl, Piriteze and Zirtek) and Loratadine (known as Clarityn) are two which may be recommended. Both are non-sedating antihistamines, meaning they are unlikely to make the patient feel drowsy. Chlorphenamine (Piriton) is an ‘old school’ antihistamine, which can make the patient sleepy, and shouldn’t be used by anyone driving or handling machinery.

For people at risk of anaphylaxis, antihistamines are usually prescribed alongside injectable adrenaline. They are intended for mild or early symptoms, but adrenaline should always be used when a severe allergic reaction is suspected.

Adrenaline

Adrenaline (also called epinephrine) is the recommended first line treatment for people with anaphylaxis.

The following notes are intended as general information only. Healthcare professionals should be guided by the medical literature. Links are provided at the foot of the page.

What form does adrenaline take?

Pre-loaded adrenaline injection kits, Jext, Emerade and EpiPen are available on prescription for those thought to be at risk of a severe reaction.

Emerade is a pre-filled syringe encased in an auto-injector. It delivers a single dose of adrenaline when pressed against the muscle of the outer thigh.

Distributor:
Bausch + Lomb UK Limited
106-114 London Road
Kingston upon Thames
KT2 6TN
United Kingdom

+44 (0)208 781 0001

[email protected]

Epipen has a spring-loaded concealed needle that delivers a single measured dose when the pen is jabbed against the muscle of the outer thigh.

Distributor:
Meda Pharmaceuticals Ltd
Skyway House
Parsonage Road
Takeley
Bishop’s Stortford
CM22 6PU

Tel 0845 460 0000.

Jext has a locking needle shield which engages after use, designed to protect against needle stick injury.

Distributor:
ALK-Abelló Ltd
1 Manor Park
Manor Farm Road
Reading
Berkshire RG2 0NA

Tel: 0118 903 7940.

Who should be prescribed adrenaline?

Allergic reactions vary in severity.

In its 2014 guidelines, the European Academy of Allergy and Clinical Immunology suggests the following:

Absolute indications for adrenaline auto-injector:

• Previous anaphylaxis triggered by food, latex, or aeroallergens
• Previous exercise-induced anaphylaxis
• Previous idiopathic anaphylaxis
• Co-existing unstable or moderate to severe, persistent asthma and a food allergy*
• Venom allergy in adults with previous systemic reactions (not receiving maintenance VIT) and children with more than cutaneous/mucosal systemic reactions
• Underlying mast cell disorders or elevated baseline serum tryptase concentrations together with any previous systemic allergic reactions to insect stings, even in VIT-treated patients

Consider prescribing adrenaline auto-injector with any of the following additional factors (especially if more than one is present)

• Previous mild-to-moderate allergic reaction* to peanut and/or tree nut
• Teenager or young adult with a food allergy*
• Remote from medical help and previous mild-to-moderate allergic reaction to a food, venom, Latex, or aeroallergens
• Previous mild-to-moderate allergic reaction to traces of food*

Notes *Excluding pollen food syndrome (oral allergy syndrome).
Muraro,A. et al. (2014) “Anaphylaxis: guidelines from the European Academy of Allergy and Clinical Immunology”. Allergy 69 (7) online early view article.

The decision to prescribe adrenaline should be part of an approach that includes a thorough assessment of the patient. This can ideally be done at a specialist allergy clinic or by a doctor who has had training in allergy management.

How is adrenaline administered?

Emerade, EpiPen, and Jext are injected into the muscle in the outer thigh. Patients need to discuss this with their GP or allergist so they are clear on this point.

Guidance is given at Emerade, at Epipen, and at Jext

What is the dose?

EpiPen 

EpiPen delivers a 300mcg dose in adults and children weighing over 25kg. Junior versions deliver a 150mcg dose for infants and children who weigh between 7.5kg and 25kg.

Jext

Jext delivers a 300mcg dose in adults and children weighing over 30kg. Junior versions deliver a 150mcg dose for people who weigh between 15kg and 30kg.

Emerade

Children between 15 kg and 30 kg — Emerade 150mcg
Patients over 30 kg — Emerade 300mcg or Emerade 500mcg
Children weighing less than 15kg may be prescribed an injector at the prescriber’s discretion.

* Emerade 150mcg is currently unavailable *

How many should be prescribed?

There is no consensus among experts about how many devices to prescribe for each person. Some advise that patients should have one device at each site that they regularly attend (for example, home, school). Others advise there should be two devices in each location, in case one is broken or misfires, or a second injection is needed before emergency help arrives. This would be particularly important if the patient is going to a remote location where prompt medical attention is unavailable. Each individual patient must be guided by their GP or allergist.

Is adrenaline dangerous?

Used correctly, adrenaline injectors are safe for the vast majority of people who carry them. Used incorrectly (such as injected into the wrong place) there could be problems. Training and re-training are essential. Based on the current evidence, the benefit of using appropriate doses of adrenaline into the correct site (the muscle of the outer thigh) far exceeds the risk.

Does adrenaline have any important drug interactions?

Anaphylaxis may be made worse by Beta blockers and these drugs decrease the effectiveness of adrenaline. Other drugs may also be contra indicated.

Is adrenaline infallible?

There is good evidence to show that adrenaline injectors, when used correctly, reverse the symptoms of a severe allergic reaction. However, adrenaline will be effective only if it is available at all times, is used correctly and is used promptly.

Early use of adrenaline leads to improved outcomes. Evidence in the medical literature suggests that a delay may lead to a poor outcome. This emphasises how important it is to obtain detailed guidance from a medical professional.

The European Medicines Agency (EMA) carried out a review of adrenaline auto-injectors following concerns that currently available adrenaline injectors may deliver adrenaline under the skin instead of into a muscle, thus delaying response to treatment.

In June 2015 the European Medicines Agency (EMA) recommended several measures, including the introduction of more effective educational material, to ensure that patients and carers use adrenaline auto-injectors successfully.

People who are overweight should be aware of the possibility that the needle may not reach the muscle. This does not necessarily mean there will be no beneficial effect. However this too needs careful discussion with a medical professional.