Thank you Avocado but your GP's advice is I think not current thinking. The consultant allergy doctors who publish guidance all talk about using the epipen as quickly as possible.
See here from the BMJ.
Myth 4: ‘Epinephrine is dangerous’
Epinephrine given by intramuscular injection into the outer mid-thigh is very safe and starts to work within minutes. Epinephrine can either be injected using a needle–syringe (using 1:1000 epinephrine, which results in a lower volume, less painful injection than if using 1:10 000) or by autoinjector device (eg, Emerade, EpiPen, Jext). Where an autoinjector is used, note that both EpiPen and Jext are only available in 150 µg and 300 µg doses, which means that the 300 µg is effectively an underdose in someone over 30 kg (this may explain why some patients require a second epinephrine dose). Younger children should be transitioned to a 300 µg dose when their body weight is >25 kg, and some centres advocate doing so from 20 kg. Around 10%–20% of patients report transient effects including pallor, anxiety, palpitations, dizziness and headache (although these symptoms may also be due to the reaction and/or the patient’s own endogenous epinephrine production).
Epinephrine is underused in the treatment of anaphylaxis, both prehospital and in emergency departments.6 10 21 23 28 Further intramuscular doses of epinephrine should be administered in the event of persisting respiratory or cardiovascular symptoms. Epinephrine can and should be repeated after 5 min; the administration of other medication such as antihistamines or steroids must not cause delay or distraction, as these are not first-line (or even second-line) treatments for anaphylaxis24 (figure 2A). An alternative summary of anaphylaxis treatment, consistent with national and international guidelines, is shown in figure 2B.
Figure 2
Download figure
Open in new tab
Download powerpoint
Figure 2
Acute management of anaphylaxis. (A) Current UK Resuscitation Council algorithm. (B) Suggested amended algorithm by the authors, which emphasises the need for further doses of intramuscular epinephrine in the event of ongoing anaphylaxis symptoms and incorporates a low-dose epinephrine infusion protocol used widely in Australia and Spain (with permission, from Brown SG, Emerg Med Australas. 2006;18:155–69).
Myth 5: ‘Antihistamines can be used to treat anaphylaxis initially; epinephrine is only needed if symptoms worsen’
Histamine is only one of many inflammatory mediators released during anaphylaxis. Oral antihistamines take around 30 min for onset of effect; intravenous chlorphenamine has a faster onset, but can cause hypotension. Antihistamines are not effective against anaphylaxis: their prophylactic use during controlled immunotherapy does not prevent anaphylaxis, and any apparent response during acute management of reactions is most likely due to the patient’s own endogenous epinephrine.29 Antihistamines have now been relegated to third-line therapy in international guidelines; their use is limited to the relief of cutaneous symptoms and should never delay the administration of epinephrine or fluid resuscitation during patient stabilisation.10
Myth 6: ‘Corticosteroids prevent delayed or biphasic reactions in anaphylaxis’
Historically, corticosteroids have been used to prevent protracted and biphasic reactions (the latter defined as a recurrence of symptoms within 72 hours of initial anaphylaxis, without re-exposure to the trigger). However, this has never been tested in a randomised clinical trial; more recent evidence has cast doubt over their efficacy.30 A recent systematic review and meta-analysis included 27 studies with 4114 anaphylaxis cases, of whom 192 (4.7%) had biphasic reactions.31 Steroid administration did not affect the likelihood of a late phase reaction (OR 1.52, 95% CI 0.96 to 2.43). In fact, there was a non-significant trend towards increased risk, although this is probably because steroid use was more common with severe reactions. Biphasic reactions were more common where hypotension was present at initial reaction (OR 2.18, 95% CI 1.14 to 4.15), but this is unusual in food-induced anaphylaxis. The median time to onset of biphasic symptoms was 11 (range 0.2–72) hours, that is, 50% of reactions occurred >11 hours after initial reaction. This is relevant because current guidance from the National Institute for Health and Care Excellence recommends patients over 16 years are observed for 6–12 hours after anaphylaxis (children under 16 should be admitted).32 In reality, it is generally accepted that prolonged observation may not be required following a straightforward reaction in someone who already has a comprehensive management plan and rescue medication (including epinephrine autoinjectors) in place.
Managing children at risk of anaphylaxis
Although research in ongoing into potential treatments for food allergy, the mainstay of management remains dietary avoidance and provision of a management plan/rescue medication in the event of accidental reactions.
Myth 7: ‘Only children who have had anaphylaxis need an epinephrine autoinjector’
Allergy skin prick tests and/or allergen-specific IgE blood tests do not predict reaction severity, and anaphylaxis can occur in patients with high, low and even negative tests. A recent European Consensus concluded that it is very difficult if not impossible to accurately predict who is at risk of severe anaphylaxis: a number of risk factors acting together are involved (figure 3).9
Figure 3
Download figure
Open in new tab
Download powerpoint
Figure 3
Risk factors for severe reactions. Reproduced with permission from Dubois et al. 34 BHR, bronchial hyperresponsiveness; NSAID, non steroidal anti-inflamatory drugs; OIT, oral immunotherapy; EMS, emergency medical services.
Clearly someone with previous anaphylaxis is at risk of subsequent anaphylaxis. However, most children who present with anaphylaxis as their initial reaction do not experience further anaphylaxis. Ewan and Clark followed up 747 allergic children, of whom 220 had initial anaphylaxis to peanut/tree nuts; 25% had further accidental reactions over a median 3-year follow-up, with only one experiencing further anaphylaxis.33 Other studies report a higher rate of anaphylaxis in those with initial mild reactions. In a UK survey of 969 young people attending allergy clinics, 48% had experienced an accidental reaction in the previous year, with 245 (25%) having anaphylaxis.6 However, the occurrence of anaphylaxis is likely to depend on a number of factors, including dose or level of exposure34 (figure 3). In a unique study of 89 children with suspected peanut allergy, Wainstein et al demonstrated that up to 75% will have anaphylaxis if exposed to sufficient peanut at challenge.35 Thus, lack of prior anaphylaxis is more likely due to insufficient exposure rather than some inherent lack of predisposition. Importantly, there are no data indicating that allergic reactions get worse with each subsequent exposure. Nor is there any evidence to suggest that anaphylaxis risk ‘runs in the family’.
Various risk factors for severe anaphylaxis have been proposed, based on limited case series of fatal anaphylaxis. Interestingly, food-induced anaphylaxis is most common in the 0–5 age group, but death from anaphylaxis in this age group is rare.2 Teenagers and young adults appear to have an age-dependent predisposition towards severe outcomes, which cannot be easily explained by risk-taking behaviours.2 Asthma is considered a risk factor; however, in the UK Fatal Anaphylaxis Registry, 22% of cases did not have a prior diagnosis of asthma.2 Around 50% of children with food allergies have asthma: the vast majority will never have a severe allergic reaction, thus asthma has poor predictive value for severe reactions (although this does not negate the imperative to improve asthma control in food-allergic individuals as a means of reducing risk).9
Delays in treating with epinephrine are a risk factor for fatal outcome10 36: it is this, as well as our inability to predict severe reactions, which drives the provision of epinephrine autoinjectors. A summary of recent guidelines on who should be prescribed autoinjectors is summarised in table 1. Healthcare professionals must consider the patient/family preference: if prescription boosts patient confidence and allows them to lead a less restrictive life, then autoinjectors should be part of the management plan. However, this requires actual carriage: the autoinjectors need to be available at all times, otherwise prescription is pointless.
View inline View popup
Table 1
Factors to be considered as part of the risk assessment on whether to prescribe epinephrine autoinjectors
Controversy exists over the number of autoinjectors to be prescribed. The BSACI and ASCIA in general recommend one device (for school children, one device for home and a second for school, while in the USA, physicians will generally prescribe two devices).10 17 In 2014, following an extensive review of epinephrine autoinjectors prompted by a coronial inquest, the Medicines and Healthcare products Regulatory Agency (MHRA) issued guidance that individuals at risk of anaphylaxis should carry two epinephrine autoinjectors at all times due to ‘uncertainties about the site of drug delivery and the speed of epinephrine action within the body’, which, together with device misuse or malfunction, might result in a second dose being needed.37 The BSACI guidance (issued after the 2014 statement) recommends a single device on the basis that one dose is usually effective for most reactions. The MHRA recently reiterated its policy,38 in line with new Department of Health guidance for school children at risk of anaphylaxis39 The MHRA review also addressed a concern that in some individuals (predominantly adolescent and adult women), the needle length in some autoinjectors may be insufficient to deliver an intramuscular (rather than subcutaneous) injection, although data to inform this are limited. At the current time, prescribing practice remains divided among UK healthcare professionals.
Myth 8: ‘Epinephrine autoinjectors are overprescribed and overused in anaphylaxis’
Autoinjectors are underused to treat anaphylaxis in the community. In a study of infants aged 3–15 months with anaphylaxis (US definition), epinephrine was administered in under one-third, most commonly because the caregiver did not recognise the severity of reaction or the autoinjector was not available.40 In a UK study, only 16.7% of young people used an autoinjector to treat anaphylaxis, the most common reason being they did not recognise that the reaction needed treatment with epinephrine.6 A Scottish study among adolescents with previous anaphylaxis reported a number of barriers to the effective use of autoinjectors, including failure to recognise anaphylaxis, uncertainty and fear over how and when to use the autoinjector, and lack of carriage due to size/design.41 In the USA, these issues have led to some management plans (by FARE) offering the suggestion to use an epinephrine autoinjector for all reactions regardless of severity, but this remains controversial and is not accepted as standard practice among many healthcare professionals.42 It must be noted that anaphylaxis morbidity/mortality is no lower in the USA compared with UK and Australia where epinephrine is only recommended for reactions with respiratory or cardiovascular involvement36
Myth 9: ‘Prescription of an epinephrine autoinjector in isolation is life-saving’
Optimal management of food-allergic patients and treatment of anaphylaxis has many facets and is not limited to a prescription for an epinephrine autoinjector. Improving patient/carer knowledge on the recognition and treatment of anaphylaxis, and addressing the complex psychosocial dimensions of allergic emergencies, form the cornerstone of successful anaphylaxis management.6 41 One-third of fatalities in the UK occur despite timely epinephrine administration.20 Epinephrine autoinjectors potentially buy valuable minutes while an emergency medical response is summonsed. Such devices need to be prescribed as part of a comprehensive management plan, which includes advice on dietary avoidance and on when to administer epinephrine. Patients and their families need to be told to use their autoinjector in the event of any respiratory symptoms, where anaphylaxis might the cause, irrespective of severity. P