Are adrenaline autoinjectors fit for purpose? A pilot study of the mechanical and injection performance characteristics of a cartridge-versus a syringe-based autoinjector

Adrenaline auto injectors pharmacokinetic/pharmacodynamic studies and potential consequences for clinical practice

BACKGROUND

Anaphylaxis is a sudden multisystem allergic reaction which may result in a fatal outcome if not treated promptly. Guidelines worldwide suggest intramuscular adrenaline as the first-line treatment for anaphylaxis outside a perioperative reaction. Adrenaline autoinjectors (AAIs) are widely used self-administrable devices, especially in community settings. Different commercial AAIs have been authorized to be marketed in Europe. For an AAI to be efficacious, a rapid adrenaline delivery in patients, including those who are overweight or obese, resulting in an optimal cardiovascular (CV) response, is a key feature. AAIs are designed to achieve this requirement, which is reflected in their differing functional properties such as primary container selection, drug delivery mechanism (cartridge-or syringe-based), needle length, needle gauge, and adrenaline dose (150 μg, 300 μg, or 500 μg). However, the differences in functional properties across these devices may play a critical role in achieving these requirements as well as the differences in ergonomics in the handling of these devices.

THE PURPOSE OF THIS REVIEW

Considering the dynamic pharmacokinetic/pharmacodynamic (PK/PD) profiles of different AAIs marketed in Europe and their effect on adrenaline delivery, the expert panel, also serving as author for this paper have carried out a detailed analysis of the PK/PD profiles of four AAIs, namely, Anapen, Emerade, EpiPen, and Jext, to delineate the adrenaline delivery and their subsequent physiological effects on the backdrop of device characteristics, dose strength, and the skin-to-muscle distances of the participants.

Pharmacokinetics of adrenaline autoinjectors

Anaphylaxis is a medical emergency with adrenaline acknowledged as the first-line therapy. It is therefore important that patients have access to self-injectable adrenaline in the community. Manufacturers have been requested by European Medicine Regulators to generate pharmacokinetic data for these autoinjector devices. For the first time, these data provide an insight into how individual devices work in different populations, and how they compare. We undertook a thorough literature search and also accessed grey literature, using searches of medicine regulators' websites and freedom of information requests. The data demonstrate that it takes at least 5-10 min to achieve early peak plasma concentration for most devices. The specific autoinjector device seems to be the most important determinant of pharmacokinetics, with different devices giving rise to different plasma adrenaline profiles. Needle length does not seem to be the most important factor; rather, the force and speed of injection (which varies from one device to another) is likely to be of greater importance. In general, peak plasma adrenaline concentration is lower and time-to-peak concentration longer with increased skin-to-muscle depth. However, it is difficult to draw conclusions with the current available data, due to a lack of head-to-head comparisons, small numbers of study participants and the failure to acknowledge the biphasic nature of intramuscular adrenaline absorption for analysis purposes.

Autoinjector device for rapid administration of drugs and antidotes in emergency situations and in mass casualty management

There are several situations such as medical emergencies and incidents involving mass casualties where drugs and antidotes have to be administered immediately along with other first aid at the site of the event. Self-administration by the affected person or by a companion is required as a life-saving measure. Autoinjector devices (AIDs) are useful for the rapid administration of drugs and antidotes and they can also be used by those who have not been medically trained. This makes them very convenient for emergency and mass casualty management. An AID has a drug cartridge with an embedded needle for subcutaneous or intramuscular injection, which is usually painless. The drugs are delivered slowly by the AID across a large area in the muscle, which increases the absorption and the drug effects are equal to that of intravenous administration. A variety of AIDs are available, such as atropine and pralidoxime for nerve agent poisoning, epinephrine for anaphylactic shock and allergy, diazepam for seizures, sumatriptan for migraine, amikacin for antibacterial treatment, buprenorphine for pain relief and monoclonal antibodies for a variety of diseases. This review describes the published peer-reviewed literature identified by online searches of journal databases.

Bioavailability and Cardiovascular Effects of Adrenaline Administered by Anapen Autoinjector in Healthy Volunteers

BACKGROUND

The administration of adrenaline is a life-saving intervention for anaphylactic reactions. However, it has been questioned whether the needle length of the autoinjectors is sufficient to achieve genuine intramuscular delivery and optimal bioavailability.

OBJECTIVE

To assess the adequacy of Anapen, which has a relatively short needle length (10.5 mm), through a comparison of the depot localization, plasma pharmacokinetics, and cardiovascular responses of adrenaline delivered via Anapen versus a prefilled syringe with a 25.4-mm needle, which is generally used for intramuscular injections.

METHODS

This randomized, open-label, crossover study compared the impact of adrenaline administration at 2 sites in the thigh of 18 normal weight male volunteers, using either Anapen or the prefilled syringe; in addition, we studied the treatment of 12 overweight women with Anapen. The depot depth was measured by ultrasonography, plasma adrenaline level was evaluated by ultra performance liquid chromatography-mass spectrometry (UPLC-MS), and heart rates were measured using a Holter monitor.

RESULTS

Intramuscular injections were given with both devices at both thigh sites in nonobese men, but not in overweight women. Adrenaline levels showed a double peak, with parallel changes in the heart rate. The first peak, of potential vital importance in anaphylaxis treatment, occurred at approximately 10 minutes postinjection, with maximum concentration and area under the curve significantly higher with Anapen than with prefilled syringes; the magnitude of the second peak did not differ among the various conditions. Unexpectedly, in overweight women treated with Anapen, the magnitude of the first peak was similar to that observed in men, despite the injection being subcutaneous, and the overall bioavailability was enhanced.

CONCLUSIONS

Needle length and intramuscular injection are not absolute requirements for autoinjector efficacy, but the monitoring of injection location, biphasic adrenaline levels, and cardiovascular responses is important for the assessment of their therapeutic relevance in anaphylaxis.

Learning and Treatment of Anaphylaxis by Laypeople: A Simulation Study Using Pupilar Technology

An anaphylactic shock is a time-critical emergency situation. The decision-making during emergencies is an important responsibility but difficult to study. Eye-tracking technology allows us to identify visual patterns involved in the decision-making. The aim of this pilot study was to evaluate two training models for the recognition and treatment of anaphylaxis by laypeople, based on expert assessment and eye-tracking technology. A cross-sectional quasi-experimental simulation study was made to evaluate the identification and treatment of anaphylaxis. 50 subjects were randomly assigned to four groups: three groups watching different training videos with content supervised by sanitary personnel and one control group who received face-to-face training during paediatric practice. To evaluate the learning, a simulation scenario represented by an anaphylaxis' victim was designed. A device capturing eye movement as well as expert valuation was used to evaluate the performance. The subjects that underwent paediatric face-to-face training achieved better and faster recognition of the anaphylaxis. They also used the adrenaline injector with better precision and less mistakes, and they needed a smaller number of visual fixations to recognise the anaphylaxis and to make the decision to inject epinephrine. Analysing the different video formats, mixed results were obtained. Therefore, they should be tested to evaluate their usability before implementation.

Effects of Epinephrine Auto-Injector Shape and Size on Human Factors Influencing Drug Delivery

OBJECTIVE

The aim of this study was to assess the effects of (a) auto-injector form factor on maximum applied force capability and (b) auto-injector design and instructions on force production and orientation.

BACKGROUND

Effective delivery of epinephrine through an auto-injector is the result of a multitude of design factors. At minimum, the design needs to allow the user to apply sufficient force for the needle to penetrate clothing and tissue.

METHOD

Trainer devices for three commercially available epinephrine auto-injectors with different form factors (cylindrical, elliptical, prismatic) were tested in a laboratory-based repeated-measures experiment with 20 adults. Participants applied their maximum force onto a force plate positioned over their thigh and practiced an injection using the trainer device after viewing training videos. Participants also rated force confidence and preference.

RESULTS

The maximum force varied significantly across devices. The greatest force observed was 64 newtons with the elliptical device, and the lowest force was 61 newtons with the cylindrical device. Participants reported the highest force confidence when using the elliptical and cylindrical devices, ranking the elliptical as their preferred device.

CONCLUSION

Force capability results for the elliptical device suggest that it may be more successful in achieving the necessary force for drug delivery in a larger set of adult users.

APPLICATION

Results suggest that the auto-injector with the elliptical form may enable more successful drug delivery among a larger set of users.

Comparison of adrenaline auto-injector devices: ease of use and ability to recall use

BACKGROUND

A limited number of adrenaline auto-injectors are currently available. Epipen and Anapen are available in Australia, New Zealand, UK and parts of Europe and Asia. Few studies have compared the performance of these devices.

OBJECTIVE

To compare the intuitiveness of use of these devices. A secondary aim was to compare the ability to recall the use of each device after a period of 3 months.

METHOD

A random sample of 100 subjects naïve to both the EpiPen and Anapen were recruited from staff and families attending Royal Children's Hospital, Melbourne Australia. Subjects were randomized to Anapen (n = 53) or EpiPen (n = 47) and asked to demonstrate use of a 'trainer' device (i) prior to and (ii) after receiving training in its correct use. A subset (n = 32) participated in a follow-up study to evaluate (iii) the ability to recall correct use of each device.

RESULTS

Most subjects correctly demonstrated all steps in use of the EpiPen and Anapen both prior to (89% vs. 79%, p = 0.17) and after training on use (100% vs. 100%). However, after 3 months, significantly more participants correctly demonstrated use of EpiPen (87%) compared to Anapen (35%) (p = 0.003) and critical errors that would likely result in failure to administer adrenaline were more common with Anapen (59% vs. 13%, p = 0.01).

CONCLUSION

Most study participants correctly demonstrated the use of both devices without prior training. There was greater attrition in correct use of Anapen compared to EpiPen over time. Critical errors in administration were more likely with Anapen than EpiPen.

Anaphylaxis treatment: ergonomics of epinephrine autoinjector design

Epinephrine administration is a critical component of individualized emergency action plans for patients at risk for anaphylaxis. Fundamental ergonomic principles can be used to facilitate rapid and effective use of an epinephrine autoinjector when appropriate. Specific patient characteristics, including age and strength, that impact physical and cognitive capabilities, should be considered when choosing an epinephrine autoinjector. Considerations in the optimal functioning of an autoinjector include the device being portable, identifiable, safe, and effective. Size, shape, coloring, and labeling of the device all contribute to the device being portable and identifiable. Trigger-lock features, designs resistant to physical perturbations, and safety technology to prevent injury after use contribute to safety and reliability. Optimal grip designs, tailored in size and/or shape to specific patient types, contribute to reliability and effectiveness. After selection of the most appropriate autoinjector, hands-on training, practice, and drills should be implemented.

Comparison of the robustness and functionality of three adrenaline auto-injectors

BACKGROUND

Anaphylaxis is a medical emergency that requires the intramuscular injection of adrenaline using an adrenaline auto-injector (AAI). This study compared the robustness and performance characteristics of three AAIs available in Europe.

METHODS

Three AAIs (Jext(®), EpiPen(®), and Anapen(®)) were tested in terms of the force needed to activate the AAIs, exposed needle length, injection volume, and injection time. Three conditions were used to assess robustness: base conditions, after three successive free-fall drops from 1.5 m, and after a 40 kg static load challenge. The injection depth and estimated volume of solution delivered into ballistic gelatin were also assessed.

RESULTS

Less force was required to remove the safety cap from Jext and EpiPen than from Anapen under base conditions. The required force was unaffected by free-fall drop tests, whereas the static load test significantly increased the force required to remove the safety cap from Jext (difference from base value 7.7 N; P < 0.001) and from EpiPen ( difference from base value 30.3 N; P < 0.001). Two Anapens could not be activated after the free-fall and static load tests. The mean exposed needle length was 15.36 mm (standard error [SE] 0.04) for Jext, 15.02 mm (SE 0.05) for EpiPen, and 7.49 mm (SE 0.15) for Anapen. The mean maximum injection depth in gelatin within 10 seconds was 28.87 mm (standard deviation [SD] 0.73) for Jext, 29.68 mm (SD 2.08) for EpiPen, and 18.74 mm (SD 1.25) for Anapen.

CONCLUSION

A comparison of the robustness and performance characteristics of the three AAIs showed that cartridge-based devices (Jext and EpiPen) appeared to be significantly more robust and capable of rapidly and consistently delivering the correct dose of adrenaline to the correct tissue compartment than the syringe-based Anapen. Overall, Jext performed better than EpiPen or Anapen following mechanical stress designed to mimic real-world use.