Who needs to carry an epinephrine autoinjector?
ABSTRACT
Patients who have had anaphylaxis or who are at risk of it (eg, due to food allergy or Hymenoptera hypersensitivity) should carry an epinephrine autoinjector at all times. However, the risks and benefits must be considered on an individual basis, especially in patients with atherosclerotic heart disease, elderly patients on polypharmacy, patients receiving allergen immunotherapy, those with large local reactions to insect stings, and individuals with oral allergy syndrome.
KEY POINTS
- Based on current data, there is no absolute contraindication to epinephrine for anaphylaxis. And failure to give epinephrine promptly has resulted in deaths.
- Clinicians concerned about adverse effects of epinephrine may be reluctant to give it during anaphylaxis.
- Education about anaphylaxis and its prompt treatment with epinephrine is critical for patients and their caregivers.
PATIENTS FOR WHOM THE NEED MAY BE LESS CLEAR
In other patients who may be at increased risk, the mandate for an epinephrine autoinjector is less clear, and the decision to carry one is determined on an individual basis. Such individuals are those receiving allergen immunotherapy, with large local reactions to insect stings, with oral allergy syndrome, with mastocytosis, and with drug allergy. In these cases, the benefit vs the burden of carrying an autoinjector should be discussed with the patient.
Patients on allergen immunotherapy
National guidelines recommend that all patients who receive allergen immunotherapy be monitored in the clinic under a physician’s supervision for 30 minutes after the injection. Fortunately, life-threatening reactions occurring after 30 minutes are rare. But delayed systemic reactions can occur and may account for up to 50% of such events.21
Therefore, many physicians consider it prudent for patients on immunotherapy to carry an epinephrine autoinjector, but there is no consensus. A survey22 found that 13.5% of allergists did not prescribe the autoinjector for patients on immunotherapy, while 33.3% prescribed it for all their patients on immunotherapy, and the rest prescribed based on risk.
Since there are no national guidelines on epinephrine autoinjectors for patients on immunotherapy, the decision should be based on the patient’s risks and comorbidities and informed by discussion between the individual patient and his or her allergist.
Patients with large local reactions to insect stings
From 5% to 10% of patients who have large local reactions to insect stings are at risk of systemic reactions.20
Patients with oral allergy syndrome
Oral allergy syndrome, also known as pollen-food allergy, causes itching and mild swelling of the mouth, lips, and throat after eating fresh fruits and vegetables. The prevalence ranges from 2% to 10% of patients with allergies.23
A survey of allergists found that 20% of patients with oral allergy syndrome had experienced systemic symptoms.24 The survey also showed that the decision to prescribe an epinephrine autoinjector to these patients was highly variable. Only about 30% of allergists recommend epinephrine autoinjectors to patients with oral allergy syndrome, while most believe that the decision should be based on the individual’s symptoms and risk.
More research is needed in the area of food allergy. Because data are limited, there are no national guidelines on whether these patients should carry an epinephrine autoinjector. We agree with the Joint Task Force on Practice Parameters14 recommendation that the decision be made on an individual basis following discussion between the patient and physician.
Patients with mastocytosis
Patients with mastocytosis and a history of anaphylaxis are at increased risk for systemic reactions to Hymenoptera venom.
Patients with medication allergy
Once medication allergy has been diagnosed, avoidance is usually effective, obviating the need for an epinephrine autoinjector, although the physician has the option of prescribing one.
CAUTIONS, NOT CONTRAINDICATIONS
Physicians may be reluctant to prescribe an epinephrine autoinjector because of the risk of an adverse reaction in patients with hypertension, coronary artery disease, or arrhythmias, and in elderly patients taking multiple drugs, especially drugs that can interact with epinephrine. Nevertheless, there is no absolute contraindication to the use of epinephrine in anaphylaxis.
In patients with atherosclerosis and cardiovascular disease
Epinephrine increases vasoconstriction, heart rate, and cardiac force of contraction. These effects are beneficial during anaphylaxis, but in rare cases patients have experienced myocardial infarction and acute coronary syndrome after receiving intravenous epinephrine.25 These incidents have naturally prompted reluctance to prescribe it in susceptible patients with coronary disease during anaphylaxis.
Yet epinephrine may not be solely to blame for these adverse responses. Mast cells are abundant in the heart, and their release of mediators can also result in adverse cardiac manifestations, including myocardial infarction.26
Conversely, some drugs used to treat cardiovascular disease can worsen anaphylaxis.
Beta-blockers can cause bronchospasm and decrease cardiac contractility. They can also blunt the pharmacologic effects of epinephrine. There is concern that epinephrine may produce dangerous elevations of blood pressure in patients taking beta-blockers by unopposed alpha-adrenergic stimulation and reflex vagotonic effects.27 And there is evidence that beta-blockers may increase the risk and severity of reactions. One study reported that patients taking beta-blockers are more than 8 times more likely to be hospitalized due to anaphylactoid reaction with bronchospasm.28
Beta-blockers and, to a lesser extent, angiotensin-converting enzyme inhibitors have been shown to increase the risk of anaphylaxis in the emergency department.29,30 However, some investigators have not found beta-blockers to be a risk factor. A study evaluating anaphylactoid reactions from contrast media found no statistically significant higher risk in patients taking beta-blockers.31 Similarly, a study of 3,178 patients on beta-blockers receiving venom immunotherapy or allergen immunotherapy found no increase in the frequency of systemic reactions.32 Nevertheless, overall, more studies support the hypothesis that beta-blockers may be an additional risk factor in anaphylaxis.33
Thus, clinicians treating patients with cardiovascular disease and anaphylaxis face a dilemma. Although there is concern in this population, epinephrine should not be withheld in patients with cardiovascular disease who are experiencing an anaphylactic event.33 If epinephrine is not administered, the patient could die.
Elderly patients on multiple medications
Older patients are also at risk of anaphylaxis. But clinicians are reluctant to treat older patients with epinephrine because of concerns about adverse effects.
Epinephrine dispensing rates vary substantially in different age groups: 1.44% for patients under age 17, 0.9% for those ages 17 to 64, and 0.32% for those age 65 or older.34 A Canadian study of 492 patients with anaphylaxis in the emergency department showed that those over age 50 received epinephrine less often than younger patients (36.1% vs 60.5%).35 Cardiovascular complications were more frequent in the older group, occurring in 4 (9.1%) of the 44 older patients who received epinephrine compared with 1 (0.4%) of the 225 younger patients who received it. On the other hand, the rate of adverse effects from subcutaneous epinephrine was no different in older asthma patients compared with younger patients.36
Many older patients take multiple medications, raising concern about adverse effects. Commonly prescribed medications in the elderly can affect the actions of epinephrine. Monoamine oxidase inhibitors retard the catabolism of epinephrine. Tricyclic antidepressants may decrease the reuptake of catecholamines by neurons and thus interfere with the degradation of epinephrine. Digoxin has a narrow therapeutic window and can potentially increase the risk of arrhythmias when given with epinephrine.
Although the clinician must be cautious in treating older patients who have comorbidities, these are not sufficient to withhold prescribing an epinephrine autoinjector to elderly patients at risk of anaphylaxis.
