PARIS — While anaphylaxis requires immediate adrenaline administration through autoinjection, the use of this treatment is not optimal. Therefore, the development of new adrenaline formulations (such as for intranasal, sublingual, and transcutaneous routes) aims to facilitate the drug’s use and reduce persistent delays in administration by patients and caregivers. An overview of the research was presented at the 19th French-speaking Congress of Allergology.
Anaphylaxis is a severe and potentially fatal immediate hypersensitivity reaction with highly variable and dynamic clinical presentations. It requires prompt recognition for immediate treatment with intramuscular (IM) adrenaline (at the anterolateral aspect of the mid-thigh).
One might think that this reflex is acquired, but in France, while the number of prescribed adrenaline autoinjection (AAI) devices has been increasing for a decade, reaching 965,944 units in 2022, this first-line treatment is underused. Anapen (150, 300, and 500 µg), EpiPen (150 and 300 µg), Jext (150 µg and 300 µg), and Emerade (150, 300, and 500 µg) are the four products marketed in France in 2024.
“Only 17.3% of individuals presenting to the emergency department in the Lorraine region used it in 2015,” said Catherine Neukirch, MD, a pneumologist at Hôpital Bichat–Claude Bernard in Paris, France, with rates of 11.3% for children and 20.3% for adults.
Anaphylaxis Incidence Increasing
Approximately 0.3% (95% CI, 0.1-0.5) of the population will experience an anaphylaxis episode in their lifetime. Incidence in Europe, across all causes, is estimated between 1.5 and 7.9 cases per 100,000 inhabitants per year. Although anaphylaxis is on the rise, its associated mortality remains low, ranging between 0.05 and 0.51 per million per year for drugs, between 0.03 and 0.32 per million per year for foods, and between 0.09 and 0.13 per million per year for hymenopteran venoms.
Data from the European Anaphylaxis Registry indicate that anaphylaxis manifests rapidly after allergen exposure: 55% of cases occur within 10 minutes and 80% within 30 minutes. In addition, a biphasic reaction, which can occur up to 72 hours after exposure, is observed in < 5% of cases.
While a delay in adrenaline use is associated with risk for increased morbidity and mortality, AAI significantly reduces error rates compared with manual treatments involving ampoules, needles, and syringes. It also reduces the associated panic risks. However, there are multiple barriers to adrenaline use. The clinical symptoms of anaphylaxis may be misleading, especially if it occurs without cutaneous and urticarial manifestations but with only acute bronchospasm. It may present as isolated laryngeal edema without digestive involvement, hypotension, or other respiratory problems.
Other limitations to adrenaline use include technical difficulties and the possibility of incorrect administration, the need for appropriate needle sizes for patients with obesity, needle phobia, potential adverse effects of adrenaline injections, failure to carry two autoinjectors, constraints related to storage and bulky transport, as well as the need for training and practice.
“These factors contribute to underuse of adrenaline by patients and caregivers,” said Dr. Neukirch, which results in delays in necessary administration.
Adrenaline Treatment Criteria?
An analysis published in 2023 based on pharmacovigilance data from 30 regional French centers from 1984 to 2022 included 42 reported cases (average age, 33 years; 26% children) of reactions to AAI, which probably is an underestimate. About 40% of AAI uses occurred during anaphylaxis. The remaining 60% were triggered outside of reactions. The main reasons were accidental injections, mainly in the fingers, and cases of not triggering the autoinjector, underlining the importance of patient education.
In 2015, the European Medicines Agency required pharmacological studies for injectable adrenaline on healthy volunteers. These studies include ultrasound measurements of bolus injection, pharmacokinetics (ie, absorption, distribution, metabolism, and excretion), and pharmacodynamics (ie, the effect of the drug and the mechanism of action in the body), with precise evaluation of cardiovascular effects (eg, systolic and diastolic blood pressures and heart rate).
Among the information collected with the different products, ultrasound studies have shown a different localization of the adrenaline bolus (ie, in muscle in patients with normal BMI and mostly in adipose tissue in patients with BMI indicating overweight and obesity). The consequences of this finding are still unknown.
In a study with 500 µg Anapen, women with overweight or obesity showed different pharmacokinetic or pharmacodynamic profiles from those in men with normal weight, with an increase in the area under the curve (0-240 min) and marked changes in the heart rate time curve.
IM administration of 0.5 mg produces rapid pharmacokinetic effects in patients with normal weight, overweight, or obesity, with a delay for the second peak in the latter case. This delay perhaps results from initial local vasoconstriction due to adrenaline.
The early peak plasma concentration occurs at 5-10 minutes for AAI, with a faster speed for Anapen and EpiPen.
Moreover, needle size is not the most important factor. Rather, it is the strength and speed of injection, which can vary depending on the AAI.
Also, the optimal plasma concentration of adrenaline to treat anaphylaxis is not known; studies cannot be conducted during anaphylaxis. In terms of pharmacokinetics, a small series discovered that increased skin or muscle thickness delays the absorption of EpiPen AAI.
Intranasal Adrenaline
To facilitate rapid adrenaline use and convince reluctant patients to carry and use adrenaline, intranasal, sublingual, or transcutaneous forms are under development.
Three intranasal forms of adrenaline are already well advanced, including Neffy from ARS Pharma, epinephrine sprays from Bryn Pharma and Hikma, and Oxero from Oragoo, which contains dry powder.
A comparison of intranasal adrenaline Neffy and AAI shows that the former has satisfactory pharmacokinetic and pharmacodynamic effects.
In a phase 1 randomized crossover study of 42 healthy adults comparing the pharmacokinetic effects of Neffy adrenaline (2 mg) and EpiPen (0.3 mg), as well as IM epinephrine 0.3 mg, several observations were made. For a single dose, the maximum concentration (Cmax) of Neffy was lower than that of EpiPen.
However, with repeated doses administered 10 minutes apart, the Cmax of Neffy was higher than that of EpiPen. At this stage, pharmacodynamic responses to intranasal products are at least comparable with those of approved injectable products.
A comparison of the pharmacodynamic effects, such as systolic and diastolic blood pressures and heart rate, of Neffy adrenaline and AAI concluded that the profile of Neffy is comparable with that of EpiPen and superior to that of IM epinephrine.
In patients with a history of allergic rhinitis, adrenaline Cmax appears to be increased, while time to peak plasma concentration (Tmax) is reduced. Low blood pressure does not prevent Neffy absorption. Neffy is currently under review by the American and European health authorities.
Intranasal absorption of dry powder adrenaline appears to be faster than that of EpiPen, thus offering a clinical advantage in the short therapeutic window for anaphylaxis treatment.
In an open-label trial conducted on 12 adults with seasonal allergic rhinitis without asthma, the pharmacokinetics, pharmacodynamics, and safety of adrenaline were compared between FMXIN002 (1.6 and 3.2 mg), which was administered intranasally with or without nasal allergen challenge, and IM EpiPen 0.3 mg. Pharmacokinetics varied by patient. Nevertheless, nasal FMXIN002 had a shorter Tmax, a doubled Cmax after the allergen challenge peak, and a higher area under the curve in the 8 hours following administration compared with EpiPen. Pharmacodynamic effects comparable with those of EpiPen were noted at 15 minutes to 4 hours after administration. The tolerance was good, with mild and local side effects. The powder seems to deposit slightly better in the nasal cavity. It remains stable for 6 months at a temperature of 40 °C and relative humidity of 75% and for 2 years at a temperature of 25 °C and relative humidity of 60%.