Intramuscular Injection Health Article

Definition

An intramuscular injection is an injection given directly into the central area of a specific muscle. In this

way, the blood vessels supplying that muscle distribute the injected medication via the cardiovascular system.

Purpose

Intramuscular injection is used for the delivery of certain drugs not recommended for other routes of administration, for instance intravenous, oral, or subcutaneous. The intramuscular route offers a faster rate of absorption than the subcutaneous route, and muscle tissue can often hold a larger volume of fluid without discomfort. In contrast, medication injected into muscle tissues is absorbed less rapidly and takes effect more slowly that medication that is injected intravenously. This is favorable for some medications.

Precautions

Careful consideration in deciding which injectable route is to be used for the prescribed medication is essential. The intramuscular route should not be used in cases where muscle size and condition is not adequate to support sufficient uptake of the drug. Intramuscular injection should be avoided if other routes of administration, especially oral, can be used to provide a comparable level of absorption and effect in any given individual's situation and condition. Intramuscular injections should not be given at a site where there is any indication of pain.

Description

Intramuscular (IM) injections are given directly into the central area of selected muscles. There are a number of sites on the human body that are suitable for IM injections; however, there are three sites that are most commonly used in this procedure.

Deltoid muscle

The deltoid muscle located laterally on the upper arm can be used for intramuscular injections. Originating from the Acromion process of the scapula and inserting approximately one-third of the way down the humerus, the deltoid muscle can be used readily for IM injections if there is sufficient muscle mass to justify use of this site. The deltoid's close proximity to the radial nerve and radial artery means that careful consideration and palpation of the muscle is required to find a safe site for penetration of the needle. There are various methods for defining the boundaries of this muscle.