An autoinjector (or auto-injector) is a medical device designed to deliver a single dose of a particular (typically life-saving) drug.
Most autoinjectors are spring-loaded syringes. By design, autoinjectors are easy to use and are intended for self-administration by patients. The site of injection depends on the drug loaded, but it typically is administered into the thigh or the buttocks. The injectors were initially designed to overcome the hesitation associated with self-administration of needle-based drugs.
Morphine is routinely carried by troops on operations and in battle in the case of injuries or severe pain. The wounded soldier is immediately injected to relieve pain, and is then usually taken back or field operated. Morphine in auto-injectors during the World Wars and the Vietnam War was common and was often used as an analgesic during field operations.
Autoinjectors are often used in the military to protect personnel from chemical warfare agents. In the U.S. military, atropine and 2-PAM-Cl (pralidoxime chloride) are used for first aid ("buddy care" or "self care") against nerve agents. An issue item, the Mark I NAAK kit, provides these drugs in the form of separate autoinjectors. A newer model, the ATNAA (Antidote Treatment Nerve Agent Auto-Injector), has both drugs in one syringe, allowing for the simplification of administration procedures. In the Gulf War, accidental and unnecessary use of atropine autoinjectors supplied to Israeli civilians proved to be a major medical problem.
In concert with the Mark I NAAK, diazepam (Valium) autoinjectors, known as CANA, are carried by US servicemembers for use in prevention of the seizures caused by nerve agents.