An epinephrine autoinjector is a medical device used to deliver a measured dose (or doses) of epinephrine (also known as adrenaline) using autoinjector technology, most frequently for the treatment of acute allergic reactions to avoid or treat the onset of anaphylactic shock.
Trade names for this device include EpiPen, Twinject, Adrenaclick, Anapen, and Jext. The EpiPen was originally derived from the ComboPen, a product developed for the military for treating exposure to nerve agents.[1]
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The devices contain a spring-loaded needle that exits the tip of the device (in some cases through a sterile membrane) and into the recipient's body to deliver the medication.
Epinephrine autoinjectors contain a pre-determined dose of epinephrine, usually between 300 μg[2][3] and 500 μg[2][4] of active ingredient at a concentration of 1:1000. Manufacturers have also made pediatric dosed versions available at 150 μg of active ingredient,[2][5] and there is also a version which contains two individual doses (in case a repeated application is required) sold under the trade name Twinject.[6]
In most countries, epinephrine is a prescription drug, and therefore obtaining the device requires a prescription from a doctor. However, in some jurisdictions, epinephrine autoinjectors are an over-the-counter drug and may be purchased from a pharmacy counter.
After activation the patient holds the device in place for 10 seconds as the epinephrine is delivered. This gives the drug enough time to be absorbed by the body's muscles and diffused into the bloodstream. Using the device intravenously is highly discouraged, and can even be lethal as epinephrine is a local vascular constrictor, and used intravenously can restrict blood flow to the area of the injection site, causing subsequent damage to extremities. Additionally, intravenous administration of the epinephrine can cause ventricular tachycardia, or dangerously rapid heartbeat.[7] After administering the device, patients are advised to seek immediate medical attention.
None of these devices prevent future episodes of anaphylaxis, but patients who experience severe or life-threatening reactions may be treated with a series of allergy injections composed of increasing concentrations of naturally occurring substances such as venom to provide excellent and usually life-long protections against adverse effects of future insect stings: the initial injections have a very low concentration, usually 1 ppb or less.[8]
On May 8, 1998, a voluntary Class I recall took place in a number of countries (the United States, Germany, Israel, Denmark, Canada, Turkey, Australia, Greece and South Africa). Epipen (0.3 mg) and Epipen Jr. (0.15 mg) epinephrine auto-injectors were recalled because certain devices originating from specific production lots were found to be ineffective in delivering medication and treating anaphylaxis.[9] This issue was resolved within the same year.
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