An epinephrine autoinjector is an emergency medication delivery device that is used on patients who have severe, life-threatening allergic reactions. The medication, a pharmaceutical adrenaline in the form of epinephrine, is administered in measured doses through an auto-injecting mechanism. Specifically, the mechanism contains a spring-loaded needle that exits one end of a plastic tube, injecting epinephrine into the body on impact. In an emergency, an epinephrine autoinjector provides temporary treatment to prevent a reaction from progressing into anaphylactic shock or to slow that progression.
Early autoinjector devices were first developed for the United States military, offering American soldiers an immediate antidote to nerve agents. Pharmaceutical companies released self-administered autoinjecting devices for civilian patients who have documented life-threatening allergies soon after that. Improvements such as autoinjectors provided patients with simple, easy methods to administer exacting doses of epinephrine. Before autoinjectors, patients carried kits that contained medication vials and a syringe, necessitating several time-consuming steps to prepare medication during a medical emergency.
Modern incarnations of epinephrine autoinjector devices are sold under several brand names. Common allergies that require the use of an epinephrine autoinjector include allergies to food, insect stings or insect bites. Reactions from exposure to certain classes of medication, such as penicillin derivatives, might also require the use of an epinephrine autoinjector.
After being exposed to a known allergen, patients who have severe allergic reactions typically have mere moments to respond before the onset of anaphylaxis and, eventually, anaphylactic shock. Depending on the severity of the allergy, life-threatening symptoms can present within minutes or even within seconds of exposure. As such, patients who have a prior history of severe allergic reactions or previous instances of anaphylactic shock are advised to carry an epinephrine autoinjector at all times. If the patient becomes exposed to an allergen and requires immediate medical intervention, an autoinjector allows for self-administration of epinephrine with no additional steps required.
Although each brand of device is slightly different in terms of internal components, the basic operation is the same. Typically, no medical training is required, because operating the device requires only a firm impact with the patient's thigh muscle. If a patient who has a known allergy to bee stings gets stung, an allergic response is nearly immediate, resulting in swelling of the face and tongue, followed by difficulty breathing. Any individual, even a child, could grasp the patient's epinephrine autoinjector and slam the tip into the patient's thigh muscle.
Upon impact with the thigh muscle, the spring-loaded needle ejects from the tube and inserts itself into the patient's muscle. Proper administration requires the patient or other individual to hold the device against the muscle for several seconds, ensuring that all medication is released. Intravenous injection or injecting the medication in another area other than the thigh muscle is strongly discouraged. Upon successful delivery of the epinephrine, emergency follow-up care is required to prevent damage to the heart from an accelerated heart rate.