Injection (medicine)

This article is about the medical procedure. For other uses, see Injection.

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A Somali boy receiving a subcutaneous injection of polio vaccine

An injection (often referred to as a "shot" or a "jab") is an infusion method of putting fluid into the body, usually with a hollow needle and a syringe which is pierced through the skin to a sufficient depth for the material to be forced into the body. An injection follows a parenteral route of administration; that is, administered other than through the digestive tract.

There are several methods of injection or infusion, including intradermal, subcutaneous, intramuscular, intravenous, intraosseous, and intraperitoneal. Long-acting forms of subcutaneous/intramuscular injections are available for various drugs, and are called depot injections.

Intramuscular injection

Main article: Intramuscular injection

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An intramuscular injection

In an intramuscular injection, the medication is delivered directly into a muscle. Many vaccines are administered intramuscularly, as well as codeine, metoclopramide, and many other medications. Many drugs injected intramuscularly are absorbed into the muscle fairly quickly, while others are more gradual. Injections to the buttocks are known to reach the bloodstream quickly due to the large amount of muscular tissue and corresponding blood supply.

Generally, intramuscular injections are not self-administered, but rather by a trained medical professional. However, prescribed self-administered intramuscular injections are becoming more common for patients who require these injections routinely.

Depot injection

A depot injection is an injection, usually subcutaneous or intramuscular, of a pharmacological agent which releases its active compound in a consistent way over a long period of time. Depot injections are usually either solid or oil-based. Depot injections may be available as certain forms of a drug, such as decanoate salts or esters. Examples of depot injections include Depo Provera and haloperidol decanoate.

The advantages of using a long-acting depot injection include increased medication compliance due to reduction in the frequency of dosing, as well as more consistent serum concentrations. A significant disadvantage is that the drug is not immediately reversible, since it is slowly released.

Hypodermic injections in nature

Various animals, and some plants, have been injecting for various reasons long before humans began doing so. This process is often called stinging. Some examples include:

• Snakes, wasps, scorpions: poison, to kill prey and self-defense.
• Some bees: poison, for self-defense and to defend their nests.
• Cnidaria (jellyfish, etc.): poison, to kill prey.
• Stinging nettles: poison, to try to avoid being eaten.

Injection pain

The pain of an injection may be lessened by prior application of ice or topical anesthetic or simultaneous pinching of the skin. Recent studies suggest that forced coughing during an injection stimulates a transient rise in blood pressure which inhibits the perception of pain. Sometimes, as with an amniocentesis, a local anesthetic is given. The most common technique to reduce the pain of an injection is simply to distract the patient.

Babies can be distracted by giving them a small amount of sweet liquid, such as sugar solution during the injection, which reduces crying.

See also

• Intracardiac injection
• Intraarticular injection
• Intraosseous infusion
• Dart injection
• Jet injector
• Injection port

External links

• Information about injections from the Merck Manual
• FDA Center for Drug Evaluation and Research Data Standards Manual: Route of Administration
• Educational Intramuscular Injection video produced by the US Army

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