Faster and more reliable absorption of adrenaline by aerosol inhalation than by subcutaneous injection

A Clinical Practice Guideline for the Emergency Management of Anaphylaxis (2020)

Background: For anaphylaxis, a life-threatening allergic reaction, the incidence rate was presented to have increased from the beginning of the 21st century. Underdiagnosis and undertreatment of anaphylaxis are public health concerns. Objective: This guideline aimed to provide high-quality and evidence-based recommendations for the emergency management of anaphylaxis. Method: The panel of health professionals from fifteen medical areas selected twenty-five clinical questions and formulated the recommendations with the supervision of four methodologists. We collected evidence by conducting systematic literature retrieval and using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach. Results: This guideline made twenty-five recommendations that covered the diagnosis, preparation, emergency treatment, and post-emergency management of anaphylaxis. We recommended the use of a set of adapted diagnostic criteria from the American National Institute of Allergy and Infectious Diseases and the Food Allergy and Anaphylaxis Network (NIAID/FAAN), and developed a severity grading system that classified anaphylaxis into four grades. We recommended epinephrine as the first-line treatment, with specific doses and routes of administration for different severity of anaphylaxis or different conditions. Proper dosage is critical in the administration of epinephrine, and the monitor is important in the IV administration. Though there was only very low or low-quality evidence supported the use of glucocorticoids and H1 antagonists, we still weakly recommended them as second-line medications. We could not make a well-directed recommendation regarding premedication for preventing anaphylaxis since it is difficult to weigh the concerns and potential effects. Conclusion: For the emergency management of anaphylaxis we conclude that: • NIAID/FAAN diagnostic criteria and the four-tier grading system should be used for the diagnosis • Prompt and proper administration of epinephrine is critical.

Population pharmacokinetic and pharmacodynamic modeling of epinephrine administered using a mobile inhaler

Inhaled epinephrine is a potential alternative to self-administered intramuscular epinephrine in imminent anaphylactic reactions. The objective was to develop a pharmacokinetic-pharmacodynamic model describing exposure and effects on heart rate of inhaled epinephrine. Data from a 4-phase cross-over clinical trial in 9 healthy volunteers including 0.3 mg intramuscular epinephrine, two doses of inhaled epinephrine (4 mg/mL solution administered during [mean] 18 and 25 min, respectively) using a mobile pocket inhaler, and an inhaled placebo were analyzed using mixed-effects modeling. Inhaled epinephrine was available almost immediately and more rapidly than via the intramuscular route (absorption half-live 29 min). Epinephrine plasma concentrations declined rapidly after terminating inhalation (elimination half-life 4.1 min) offering the option to stop exposure in case of adverse events. While the expected maximum concentration was higher for inhaled epinephrine, this was not associated with safety concerns due to only moderate additional hemodynamic effects compared to intramuscular administration. Bioavailability after inhalation (4.7%) was subject to high interindividual and interoccasional variability highlighting that training of inhalation would be essential for patients. The proposed model suggests that the use of a highly concentrated epinephrine solution via inhalation may offer an effective treatment option in anaphylaxis, while efficacy in patients remains to be shown.

Pharmacokinetics and pharmacodynamics of moist inhalation epinephrine using a mobile inhaler

BACKGROUND

Intramuscular (L-)epinephrine is used as self-medication for serious hypersensitivity reactions. Inhalative administration has the theoretical advantage of a more rapid absorption and better controllability.

OBJECTIVES

The current trial was conducted to explore pharmacokinetics and pharmacodynamics of two nebulized inhalative epinephrine doses (4 mg and 8 mg in aqueous solution) using a mobile pocket inhaler relative to intramuscular administration (0.3 mg) and placebo.

METHODS

This randomized, open-label, change-over pilot study involved eight young healthy men and women. Noncompartmental pharmacokinetic and pharmacodynamic parameters were calculated from epinephrine plasma concentrations and hemodynamic parameters.

RESULTS

Mean exposure to epinephrine decreased from the 8 mg dose to the 4 mg inhalative dose, and further with the 0.3 mg intramuscular dose, with active treatments showing significantly higher concentrations than placebo (geometric mean area under the curve AUC0-t(last) values: 282, 236, 204 and 81.6 hr*ng/L). Maximal concentrations were reached within approximately 15 min for all active treatments. Epinephrine effects for inhalative administrations on heart rates were significantly higher than those for the intramuscular or placebo administration, while no excessive effects occurred. Pronounced overall variability prohibited a definite assessment of relative bioavailability between treatments. However, results indicated that epinephrine concentrations obtained following the 8 mg inhalative dose were not inferior to those after 0.3 mg i.m.

CONCLUSIONS

A relevant fraction of moist inhalation epinephrine doses is absorbed and mediates systemic effects. This suggests that administration of epinephrine via a suitable pocket inhaler device may be beneficial in ambulatory emergency treatment of systemic hypersensitivity reactions. EudraCT number: 2010-021493-11.

Use of epinephrine in the treatment of anaphylaxis

PURPOSE OF REVIEW

This paper is intended to review recent literature that impacts the use of epinephrine in the therapy of anaphylaxis.

RECENT FINDINGS

The most important recent finding regarding the administration of epinephrine is that the intramuscular route of administration is the route of choice for the treatment of anaphylaxis, and the lateral aspect of the thigh is the site of choice. In addition, recent research emphasizes the fact that epinephrine is grossly underused in the management of anaphylaxis, which accentuates the need for further education of both physician and patient in this regard.

SUMMARY

Several major themes have emerged from this review of the recent literature. The finding that the intramuscular route of administration for epinephrine is superior has now been recognized by the guidelines, and because the site of choice has been found to be the lateral aspect of the thigh, the needle used for injection must be long enough to penetrate the vastus lateralis muscle. The reasons for the underutilization of epinephrine in the treatment of anaphylaxis are also discussed. Other important findings include the fact that outdated EpiPens can usually be administered safely, and alternative routes of administration, which may be more acceptable to patients, may be on the horizon as a result of preliminary studies assessing the administration of sublingual epinephrine by wafer. Finally, it is now understood that epinephrine prescription data may be one of our best tools to study the epidemiology and incidence of anaphylactic episodes.

The role of epinephrine in the treatment of anaphylaxis

Epinephrine is the cornerstone of anaphylaxis management. Its administration should be immediate upon evidence of the occurrence of anaphylaxis. Delays in administration may be fatal. The most appropriate administration is 0.3 to 0.5 mL of 1:1000 dilution intramuscularly for adults and 0.01 mg/kg for children, given in the lateral thigh. Patients with known anaphylactic reactivity should be prescribed an epinephrine auto-injector to be carried at all times for treatment of potential recurrences. Education of the patient or parent regarding the proper use of this tool is paramount.