An injection is a method of putting liquid into the body 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 injection, that is, its effect is not necessarily local to
the area in which the injection is administered; it is systemic.
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.
There are several types of injections or infusions, including,
subcutaneous, intramuscular, and intravenous infusions. Long-acting forms of
subcutaneous/intramuscular injections are available for various drugs; these are
called depot injections.
Examples of medications that are sometimes administered
* Interferon beta-1a
* sex hormones, such as testosterone, estradiol valerate, and
* quinine in its gluconate form
In addition, some vaccines are administered intramuscularly:
* 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.