12.6: Administering Intramuscular Injections

Learning Objectives

By the end of this section, you will be able to:

• Describe the guidelines for using the intramuscular (IM) route for medication administration
• Identify common medications administered via the IM route
• Demonstrate the steps for administering IM injections

Parenteral medications injected into a muscle are known as intramuscular (IM) injections. This route allows for rapid absorption of medications; therefore, certain medications are well-suited for the IM route. The nurse must be able to accurately perform the steps for administration, including selecting an appropriate muscle and needle size, and using proper technique. This section will provide you with the knowledge to safely administer medications via the IM route.

Guidelines for Using the IM Route

Medications administered via the intramuscular route are injected directly into the muscle. Muscle tissue has a large blood supply; therefore, IM medications may be absorbed faster than those injected via the SQ route. However, any factor that affects blood flow will adversely affect the rate of absorption. Proper administration techniques must be followed to avoid complications, such as muscle atrophy, injury to the bone, abscesses, pain, nerve injury, and cellulitis. To ensure the medication is administered into the muscle, careful consideration must be given to selecting an appropriate anatomical site for the IM injection.

Anatomical Sites for IM Injections

When administering medications via the IM route, it is important to select an appropriate anatomical site. Site selection depends on a number of factors, including the patient’s age, condition, type of medication to be administered, and volume of medication required. The most commonly used sites for adults and children greater than 18 months old include the deltoid, vastus lateralis, and ventrogluteal muscles. For children less than 18 months old, the vastus lateralis of the thigh should be used because it is the most developed muscle at that age.

The deltoid (Figure 12.31) is a triangle-shaped muscle in the upper arm that is easy to locate and access. The injection site is in the middle of the deltoid muscle, approximately 1 to 2 in (2.5 to 5 cm) below the acromion process. To locate the deltoid muscle, expose the upper arm and have the patient relax their arm. Locate the acromion process (bony prominence of the scapula) and lay three fingers horizontally below the acromion process (Figure 12.31). Three finger’s breadth from the acromion process typically falls in the middle of the muscle, which helps reduce the risk of injecting the medication into the subcutaneous tissue, nerves, or joints.

Figure 12.31 (a) The deltoid is a triangular muscle that can (b) be located on the outer aspect of the shoulder. (credit a: modification of “Im-deltoid” by British Columbia Institute of Technology/Wikimedia Commons, CC BY 4.0; credit b: modification of “Sept-22-2015.11.jpg” by British Columbia Institute of Technology, CC BY 4.0)

The vastus lateralis (Figure 12.32) is located on the anterior lateral aspect of the thigh. It extends from one hand’s breadth above the knee to one hand’s breadth below the greater trochanter. The vastus lateralis is the preferred site for children less than 18 months old because typically this muscle is well-developed. To locate the site, have the patient lie flat with their knees slightly bent or move to a sitting position.

Figure 12.32 This illustration shows where to locate the vastus lateralis site. (credit: modification of “Im-vastus-lateralis.png” by British Columbia Institute of Technology/Wikimedia Commons, CC BY 4.0)

The ventrogluteal site (Figure 12.33) involves the gluteus medius and minimus muscles. It is considered to be one of the safest intramuscular sites because of the thickness of the gluteal muscles, the thinness of the fat, and the lack of nerves and blood vessels present. It is also the preferred site for solutions that are oily or known to be irritating. After the patient is positioned in the supine or lateral position (on their side), the nurse feels for the hip. Using the left hand for the right hip or your right hand for the left hip, the nurse places the palm on the greater trochanter, with the thumb pointing toward the umbilicus. The nurse moves the index finger toward the anterior superior iliac spine and the middle finger toward the iliac crest to create a V shape between the index and middle fingers.

Figure 12.33 This illustration demonstrates how to locate the ventrogluteal site for IM medication injections. (credit: modification of “Im-ventrogluteal-300x244.png” by British Columbia Institute of Technology/Wikimedia Commons, CC BY 4.0)

The site selected should be free from pain, infection, abrasions, and necrosis. Avoid sites with atrophied muscle because the muscle may not be able to absorb the medication. Avoid the dorsogluteal site unless otherwise recommended because of the increased risk of injury including sciatic nerve damage and paralysis of the leg. Rotating sites should be considered if IM injections are repeatedly administered to decrease the risk of hypertrophy.

Common Medications Given Intramuscularly

Intramuscular injections may be used to administer a variety of medications because of the quick absorption rate and prolonged action. Provided the size of muscle tissues, the IM route is preferred to the ID and SQ routes when larger volumes of fluid need to be administered or the solution may be concentrated or viscous. Examples of medications that may be administered via the IM route include narcotics, antibiotics, vaccinations, immunoglobulins, and hormonal medications.

Narcotics

Narcotics administered via the IM route have a slower and more variable onset than when administered via the IV route. Caution must be taken when injecting narcotics into chilled bodily areas or in patients with hypotension or shock. These circumstances prevent complete absorption of the medication; therefore, repeated injections may cause excessive amounts of the medication to be absorbed at once if normal circulation is re-established. Common narcotics administered via the IM route include meperidine (Demerol), morphine, and fentanyl.

Clinical Safety and Procedures (QSEN): QSEN Competency: What to Do If a Reaction Occurs

Intramuscular injections may cause an injection site reaction. Symptoms of an injection site reaction include redness, swelling, warmth, mild pain or discomfort, itching, or a lump under the skin. Usually, these symptoms are not dangerous and subside within one to two days. To reduce the pain and provide comfort for the patient, warm or cold compresses may be applied in ten- to twenty-minute increments, over-the-counter pain relievers may be administered, and diphenhydramine (Benadryl) may be provided to reduce itching.

More serious symptoms, such as fever, hives, trouble breathing, severe pain, joint pain, blisters at the injection site, and facial swelling may indicate a more serious reaction to the medication and should always be communicated to the provider. In these instances, the patient may be experiencing anaphylaxis and may need emergent treatment, such as cardiopulmonary resuscitation, an epinephrine injection, or other emergency medications. The onset of action with IM narcotics is variable; therefore, the patient must also be monitored for potential overdose. Should an overdose occur, naloxone (Narcan), an opioid antagonist, may be administered intramuscularly to reverse the effects of the narcotic medication.

Antibiotics

Intramuscular antibiotics may be indicated to treat bacterial infections, as well as when the patient is unable to tolerate oral medications or when the patient is noncompliant with taking medications. Common antibiotics administered via the IM route include penicillin, streptomycin, and ceftriaxone (Rocephin). Depending on the required dose, it may be necessary to inject more than one shot within a single dose (see Volume Limits for Different Routes). Antibiotics, such as penicillin, are administered by deep IM injection into the ventrogluteal site. Gently massaging the injection site or walking around may help to alleviate some of the pain associated with administering antibiotics via the IM route.

Vaccinations

Vaccines are one of the most commonly administered IM injections. The deltoid is the preferred site for most adult vaccinations, whereas the vastus lateralis is the preferred site for children less than 18 months old. There are no large blood vessels near these preferred sites; therefore, there is very little risk of the vaccine entering the bloodstream, so do not aspirate when administering vaccines. If administering more than one vaccine, leave at least 1 in (2.5 cm) between vaccination sites, if possible. Vaccines commonly administered via the IM route include influenza, COVID-19, hepatitis A, hepatitis B, meningococcal, pneumococcal, tetanus, and human papillomavirus.

Life-Stage Context: Administering Vaccinations to Children

Injections can be scary for children and may invoke anxiety. Nurses play a critical role in creating a positive immunization experience for the patient. When administering vaccines to children, it is important to pay attention to facial expressions, body language, and comments; use a safe, calm voice; make eye contact with the child not just the parent; explain why the vaccine is needed in words the child can understand; and be honest about what the child may experience during the procedure. To reduce fear and pain, refer to the medication as a “vaccine” instead of a “shot,” which has a negative connotation. Also, allow children to sit upright instead of having them lay down. Parent participation has also been shown to increase children’s comfort level. Therefore, the parent should be encouraged to hold the child during administration of the vaccine. The parent should be instructed on how to help hold the child still during the injection, such as swaddling an infant, having the child sit in their parent’s lap with their legs positioned between their parent’s thighs, and bear-hugging the child’s arms. Depending on the dose of the medication and the size of the patient, the dose may need to be divided between more than one site to adhere to volume limits per muscle. After the procedure, always praise the child for being brave throughout the procedure.

Older children and adolescents may be at risk of fainting after vaccinations. Before administering a vaccine, ask the patient if they have ever fainted. If so, position the patient so they are lying down to enhance safety should they faint. Be aware of symptoms such as weakness, dizziness, and pallor, which may indicate the onset of fainting. If any of these symptoms are present, have the patient lie down and monitor them for fifteen to twenty minutes after the injection. After symptoms resolve, instruct the patient to move in small increments, such as sitting upright with the legs elevated, then lowering the legs, and then finally standing.

Immunoglobulins

Immunoglobulins are antibodies that are administered to help fight infections. They are made from healthy human blood that contains high levels of antibodies. Immunoglobulins should be administered as soon as possible after having been exposed to infection because they may not be effective if too much time has passed since the exposure. Immunoglobulins are commonly administered via the IM route for exposures to hepatitis A, measles, chicken pox, or rubella. Side effects of immunoglobulins include muscle stiffness, redness, warmth, pain, and tenderness at the injection site. Immunoglobulins are created using human blood; therefore, they may contain substances that could cause infection, though rare. Therefore, it is important to consider the risks and benefits of the medication and to report persistent sore throat/fever, yellowing of the eyes or skin, or dark urine. Consideration should also be given to any live vaccines that may have recently been administered because the response of these vaccines may be reduced with subsequent administration of immunoglobulins.

Hormonal Medications

Hormonal medications may be given to replace a hormone when the body does not make enough of it. Common hormonal medications administered via the IM route include testosterone, estrogen, and progesterone. These medications are prepared in a liquid form suspended in oil. Typically, hormonal medications are administered in the dorsogluteal site (the upper, outer buttocks). To identify the correct site, visually divide the buttocks into four quadrants and use the upper, outer quadrant for the injection. The buttocks contain large blood vessels; therefore, always aspirate before injecting the medication. Oil-based solutions are known to be irritating and painful for the patient. To prevent unnecessary pain for the patient, oil-based solutions should be given with 18- to 21-gauge needles because it takes more force to push the oil-based solution through smaller needles. Instructing the patient to gently massage the injection site will help to break up the oil and promote absorption. Sometimes, oil-based solutions may cause little knots to form where the oil has accumulated. To avoid tissue damage and further buildup of the oil, rotate the injection sites and do not inject within 1 in (2.5 cm) of any knot formations.

Steps for Administration of IM Injections

Safe administration of IM injections requires following proper technique. When administering IM injections, it is important to select an appropriate site for administration. After selecting the site, the nurse cleans the skin with an alcohol swab and then allows the skin to dry completely. The nurse holds the syringe at a 90-degree angle from the site with the bevel up, which allows for smooth introduction of the needle into the muscular tissue (see Figure 12.10).

When administering IM injections, the nurse holds the skin around the injection site to secure the area for injection. Grasping the muscle may be especially important with pediatric and geriatric patients who typically have less adipose tissue to ensure the needle is injected into the muscle and does not pierce through the muscle and into the bone. The nurse inserts the needle into the skin using a quick, darting motion. When the needle is inserted all the way into the skin, the nurse performs aspiration (if required by agency policy) by pulling back on the plunger to check for blood return. Lack of blood return confirms that the needle is in the muscle and not in a blood vessel. If blood return is noted, the nurse removes the needle, discards the dose, and prepares another dose of the medication. The nurse slowly injects the medication at a rate of approximately 10 seconds per mL, unless otherwise indicated. After the dose is administered, the nurse removes the needle at the same angle in which it was introduced into the skin, then applies gentle pressure to the site with a sterile gauze, engages the needle safety device, and discards the syringe in a sharps container.

Link to Learning

You can view how to administer an intramuscular medication in this video demonstration.

Clinical Safety and Procedures (QSEN): QSEN Competency: Administering an Intramuscular Injection

See the competency checklist for Administering an Intramuscular Injection. You can find the checklists on the Student resources tab of your book page on openstax.org.

The Z-track method (Figure 12.34) may be used for all IM injections when the overlying tissue can be displaced. This method creates a zigzag path that prevents the medication from leaking into the subcutaneous tissue by altering the track created by the needle. To perform the Z-track method, the nurse pulls the skin down or to the side about 1 in (2.5 cm), away from the injection site and aspirates, if required by agency policy. The nurse then slowly injects the medication while still pulling the skin down or to the side. After the medication has been administered, the nurse leaves the syringe in place for ten seconds to allow the medication to be displaced. After withdrawing the needle, the nurse then releases the skin. Displacement of the skin closes off the needle track after the skin is released.

Figure 12.34 This illustration shows how to perform the Z-track method of IM medication administration. (credit: “Z-track-process-1.jpg” and “Z-track-process-3.png” by British Columbia Institute of Technology, CC BY 4.0.)

Needle Size and Syringe Type

When administering an IM injection, it is important to select a needle appropriate for the patient’s body composition and amount of adipose tissue, age, type of medication, volume of the medication to be administered, as well as the viscosity of the medication (Table 12.2). The length of the needle must be long enough to be injected into the muscle. Typically, 5/8 to 1.5 in (16 to 38 mm) needles are used for IM injections in adults; 1.5 in (38 mm) needles are used when there is more adipose tissue present and 5/8 in (16 mm) needles are used where there is less adipose tissue. As a general guideline, a 5/8 in (16 mm) needle may be appropriate for adults weighing less than 130 lbs (59 kg), a 1 in (25.4 mm) needle may be ideal for those weighing between 130 and 260 lbs (59 and 118 kg), and a 1.5 in (38 mm) needle would be appropriate for those weighing greater than 260 lbs (118 kg). General guidelines may be formulated based on how much the patient weighs; however, the patient’s body composition and amount of adipose tissue present should also be considered. Children and infants require shorter needles. Refer to the agency’s policies regarding needle length for children.

Table 12.2 Size and Diameter of Needles

Length of Required Needle
Length of Needle	Patient’s Weight	Quantity of Adipose Tissue
5/8 in (13 mm)	< 130 lbs (59 kg)	Minimal
1 in (25.4 mm)	130 to 260 lbs (59–118 kg)	Normal
1.5 in (38 mm)	> 260 lbs (118 kg)	Large or excessive
Diameter of Required Needle
Gauge of Needle	Medication Composition
20G to 25G	Aqueous solution
18G to 21G	Viscous or oil-based solution

In addition to the length of the needle, it is also important to select the correct gauge of needle. The gauge of the needle is dependent upon the solution to be administered. Aqueous solutions may be given using a 20G to 25G needle, oil-based solutions require an 18G to 21G needle, and immunizations require a 22G to 25G needle. Typically, a 22G to 25G needle is used with children. If the solution to be injected is aqueous, a 25G needle would be the appropriate choice, whereas a 22G needle would be a better choice if the solution is viscous or oil based.

When administering IM injections, the medication may need to be withdrawn from a vial or it may come packaged as a prefilled syringe. If the medication is packaged in a vial, select an appropriate syringe according to the amount of volume to be injected, typically a 1 to 3 mL hypodermic syringe. Attach the needle to the syringe and withdraw the medication from the vial. Replace the needle with a new needle appropriate for the injection site because the needle used to withdraw the medication from the vial is dulled after it pierces the vial. If the medication is packaged as a prefilled syringe, simply attach the needle to be used for the injection to the prefilled syringe.

Clinical Judgment Measurement Model: Take Action: Selecting the Correct Needle Size

Before taking action to select the correct needle size, the nurse must first recognize the associated cues. For example, the nurse read the order for influenza vaccine 0.5 mL IM times one dose to be administered to a 25-year-old patient who weighs 150 lbs (68 kg). The nurse analyzes the cues to realize the influenza vaccine is an aqueous solution that should be administered in the patient’s deltoid muscle. Given this vaccine must be administered intramuscularly, the nurse hypothesizes that a 5/8 to 1.5 in (13 to 38 mm), 22G to 25G needle will be needed for the injection. The nurse considers the options that are available within these size ranges (generates solutions) and decides to use a 1 in (25.4 mm), 25G needle. A 1 in (25.4 mm) needle was selected from the possible lengths based on the patient’s weight of 150 lbs (68 kg), and a 25G gauge needle was selected based on the fact that the medication is an aqueous solution.