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A 0.3 mg EpiPen auto-injector.

An epinephrine autoinjector is a medical device used to deliver a measured dose (or doses) of epinephrine (commonly known as adrenalin) 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, Anapen and Twinject.



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 0.3 mg[1][2] and 0.5 mg[1][3] of active ingredient at a concentration of 1:1000. Manufacturers have also made paediatric dosed versions available at 0.15 mg of active ingredient,[1][4] and there is also a version which contains two individual doses, in case a repeated application is required, sold under the trade name Twinject.[5]

In most countries, epinephrine is a prescription drug, and therefore obtaining the device requires a prescription from a doctor. However, in some jurisdictions, for instance Canada, 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 use 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.[6] After administering the device, patients are advised to seek immediate medical attention.

1998 Recall

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.[7] This issue was resolved within the same year.

Long-term effectiveness

None of these devices prevents 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: these injections are astonishingly dilute—a billion-fold or more is common.[8]


The EpiPen was originally derived from the ComboPen, a product developed for the military for treatment for exposure to nerve agents. The inventor of the ComboPen and the EpiPen was Sheldon Kaplan, who died in September 2009.[9]

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Twinject is the registered trademark of the first epinephrine autoinjector that contains two doses. It is used in medicine as an emergency treatment for severe allergic reaction (anaphylaxis).


History and development

Twinject was originally designed and manufactured by Verus Pharmaceuticals in the United States. The Twinject was developed after some studies showed that more than one dose of epinephrine may be required in up to 35 percent of anaphylaxis cases to properly address the allergic reaction.[1] It is currently available in two models, the Twinject 0.3 mg, and the Twinject 0.15 mg, in both the United States and Canada.

United States

Twinject was released in the United States on August 16, 2005. It was the first, and currently only, two dose epinephrine autoinjector approved for use in the United States by the FDA. In the U.S. autoinjectors are a regulated medical device and require a prescription from a medical doctor. [2] The device is available in two strengths. In April 2007 Verus announced that changes were being made to the device, but the actual proposed modifications have not yet been made public.


On July 27, 2005, Verus announced that it had entered into an exclusive agreement with Paladin Labs to commercialize Twinject in Canada. Paladin released Twinject in Canada on September 22, 2005, after approval of Health Canada.[3] In Canada, Twinject is available in pharmacies. While it is available without a prescription, most patients choose to have it prescribed as it is usually covered by private and public medical insurance. In Canada, Twinject usually has a retail price between 95 CAD and 115 CAD[4].

On July 14, 2008, Health Canada issued an advisory [5] regarding the possibility of malfunctions with the Twinject 0.3 milligram auto-injector and the Twinject 0.15 milligram auto-injector. However, Health Canada's report has not resulted in a recall. Twinject remains available throughout Canada and the United States, and is deemed safe for use.[6]


On August 21, 2006, Verus announced that UCB, a European pharmaceutical company, will begin marketing and producing the Twinject for distribution in Europe. While the Twinject has yet to be sold outside Canada or the U.S., UCB has the option of commercialize the entire Twinject product line in all other territories beyond Europe (excluding the U.S. and Canada). [7] Most markets in Europe require a prescription for epinephrine autoinjectors.


The Twinject is available in two doses:

  • In an anaphylactic emergency Adults weighing 30 kilograms/66 lb or more require a dosage of 0.3 mg of 1:1000 epinephrine. The Twinject 0.3 mg includes more than three adult doses but claims to have only two adult doses. It contains 1.1 ml. In cases of emergency, one can access these "secret" doses with a syringe given IM. As well, for chronic suffers, many prefer manual IM injections rather than having an "auto-injector" used on them.
  • For children weighing 15 to 30 kilograms/33 to 66 lb, the standard dose is of 0.15 mg of 1:1000 epinephrine. The Twinject 0.15 mg contains two doses of 0.15 mg.
  • For children weighing less than 15 kilograms/33 lb a dosage of 0.01 mg/kg of 1:1000 epinephrine is recommended. As the smallest dose available with the Twinject is 0.15 mg, for children weighing less than 15 kg other forms of injectable epinephrine may need to be considered. [8]


The Twinject is used to temporarily reverse the effects of a severe allergic reaction. Advanced medical care is required immediately after administering the epinephrine.

The Twinject contains a spring-loaded needle that shoots through a membrane in the tip and into the recipient's body to deliver the medication. A patient uses the device by removing the green locking cap from the bottom of the device, then the red cap at the top, forming a fist around the unit, and jabbing it firmly into a thigh until the click of the spring-loaded needle activating is heard. The patient holds the device in place for 10–15 seconds as the epinephrine is delivered. Using the device intravenously or subcutaneously is highly discouraged.

After administering the device, patients are advised to seek immediate medical attention as epinephrine will temporarily relieve the symptoms of anaphylaxis but advanced medical care is required to permanently reverse the reaction. The second dose can be used after 10 minutes if the symptoms have not receded or if they begin to return before medical help has been reached.

To administer the second dose, the gray cap must be removed. Then, being careful with the exposed needle, the full syringe needs to be removed. Then a yellow (in the 0.3 mg dose autoinjector) or orange cap (in the 0.15 mg dose autoinjector) needs to be taken off the plunger. Then the needle can be inserted into the thigh and the plunger can be pushed completely down. It is advised that the second dose be prepared immediately following the first dose in order for it to be ready to administer when required.[8]


There are no known contraindications to the use of epinephrine in a life-threatening allergic reaction. [8]


The Twinject usually has a shelf life of about 12 months or until the epinephrine (usually a clear liquid) begins to contain a precipitate, discolor (pinkish color, or more than only a slight yellow color). Once either of these occurs the Twinject should be immediately replaced. However, in the event of a life-threatening allergic reaction, even if the epinephrine has expired, the Twinject should be used.

The Twinject should be stored between 20 and 25 °C (68 to 77 °F). During excursions, epinephrine may be kept at a temperature of 15 to 30°C (59 to 86 °F). It should not be allowed to freeze and should not be refrigerated. [4]

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