Intramuscular Injections

An intramuscular injection being administered in the bending position.

Intramuscular injection is the injection of a substance directly into a muscle. In medicine, it is one of several alternative methods for the administration of medications (see Route of administration). It is used for particular forms of medication that are administered in small amounts. Depending on the chemical properties of the drug, the medication may either be absorbed fairly quickly or more gradually. Intramuscular injections are often given in the deltoid, vastus lateralis, ventrogluteal and dorsogluteal muscles. When the gluteal muscles are used, injections should be made on the upper, outer quadrant of the buttock to avoid damaging the sciatic nerve. Injection fibrosis is a complication that may occur if the injections are delivered with great frequency or with improper technique.

Thrombocytopenia (low platelet counts) and coagulopathy (bleeding tendency) are contraindications for intramuscular injections, as they may lead to hematomas.

Examples of medications that are sometimes administered intramuscularly are:

* codeine
* methotrexate
* metoclopramide
* olanzapine
* Streptomycin
* diazepam
* prednisone
* Interferon beta-1a
* sex hormones, such as testosterone, estradiol valerate, and Depo Provera
* dimercaprol
* ketamine
* naloxone
* quinine in its gluconate form

In addition, some vaccines are administered intramuscularly:

* Gardasil

* hepatitis A vaccine

The gluteus medius muscle, which is also known as the ventrogluteal site, is the third commonly used site for IM injections. The correct area for injection can be determined in the following manner. Place the heel of the hand of the greater trochanter of the femur with fingers pointing towards the patient's head. The left hand is used for the right hip and vice versa. While keeping the palm of the hand over the greater trochanter and placing the index finger on the anterior superior iliac spine, stretch the middle finger dorsally palpating for the iliac crest and then press lightly below this point. The triangle formed by the iliac crest, the third finger and index finger forms the area suitable for intramuscular injection.