Twinject
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. It is currently available in two models Twinject 0.3mg, and the Twinject 0.15mg (see Dosing information below) 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.  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.

## Canada
On July 27, 2005, Verus announced that it had entered into an exclusive agreement with Paladin Labs to commercialize the Twinject in Canada. Paladin released the Twinject in Canada on September 22, 2005, after approval of Health Canada. In Canada the Twinject is not a regulated medical device, per se (it is kept behind the counter in pharmacies.) While it does not require a prescription, many patients choose to have it prescribed as many insurance companies will only cover the cost of the device if it is prescribed. In Canada the Twinject usually retails between $95 CAD and $115 CAD

## Europe
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).  Most markets in Europe require a prescription for epinephrine autoinjectors.

# Dosage
The Twinject is available in two doses:
- In an anaphylactic emergency Adults weighing 30 kilograms/66 lbs or more require a dosage of 0.3 mg of 1:1000 epinephrine. The Twinject 0.3mg includes two adult doses.
- For children weighing 15 to 30 kilograms/33-66 lbs, the standard dose is of 0.15 mg of 1:1000 epinephrine. The Twinject 0.15 mg contains two doses of 0.15mg.
- For children weighing less that 15 kilograms/33 lbs a dosage of 0.01mg/kg of 1:1000 epinephrine is recommended. As the smallest dose available with the Twinject is 0.15mg, for children weighing less that 15kg other forms of injectable epinephrine may need to be considered. 

# Usage
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 0.3mg dose autoinjector) or orange cap (in the 0.15mg dose autoinjector) needs to be taken off the plunger. Then can the needle 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.

## Contraindications
There are no known contraindications to the use of epinephrine in a life-threatening allergic reaction. 

# Storage
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 25C/68-77F. During excursions, epinephrine may be kept at a temperature of 15-30C/59-86F . It should not be allowed to freeze and should not be refrigerated. 

# See Also
- Anaphylaxis
- Autoinjector
- Epinephrine
- Epipen