An auto-injector is a medical device designed to deliver a premeasured dose of medication. Many variants exist; their relative ease of use by patients or other untrained persons make the auto-injector an ideal tool to quickly administer life-saving drugs. Though developed for patients hesitant of injecting their own medication, world militaries have adopted the device for soldiers who may need to administer antidotes for chemical warfare agents. As of 2011, research into creating more reliable and safe auto-injectors is ongoing.
The mechanism of an auto-injector, through more complex than of the standard syringe, is relatively simple. Before use, the patient removes a plastic cap protecting the syringe assembly. At this point, the needle is not visible as it is still within the device's housing. Placing the auto-injector against the thigh, the patient pushes a button at the opposite end of the injector. The button releases a spring which quickly inserts the needle and administers medication. Depending on the type of injector, the device might indicate when the patient can remove the needle.
Militaries around the world are some of the largest customers of auto-injectors. For example, an auto-injector containing antidotes for chemical warfare agents is standard equipment for soldiers serving in the United States armed forces. Chemical warfare agents act quickly upon the human nervous system, meaning that soldiers have only seconds to administer life-saving drugs like atropine. Atropine, though having many medical uses, is an antidote against organophosphate poisoning. Administering a single dose of atropine protects against sarin, VX, tabun and soman, some of the most common chemical warfare agents.
Though the auto-injector plays a large role protecting soldiers, civilian patients with a variety of medical conditions benefit from using the device. For example, many individuals prone to severe allergic reactions carry an epinephrine auto-injector. A patient or someone close by can use the injector to prevent anaphylactic shock. Patients with multiple sclerosis use auto-injectors containing interferon on a regular basis to slow the disease's progression. No matter the device's ease of use, patients and those who spend long periods of time with patients should learn proper techniques for administering medication.
As the auto-injector is a widely used piece of medical equipment, research continues into making better injectors. For example, as the military needs injectors with a long shelf life, newer injectors have plastic syringes rather than those made from glass. Other research has made the once bulky jet injector into a pen sized device used by diabetics to deliver insulin.