What are the primary needs for an intramuscular (IM) injection?

Intramuscular Injection Requirements

For intramuscular injections, you need a 22-25 gauge needle with length varying by age (7/8-1 inch for infants, 7/8-1¼ inches for children, and 1-1½ inches for adults), administered at a 90-degree angle into the deltoid muscle (adults) or anterolateral thigh (infants and alternative for adults). 1, 2

Needle Specifications by Age Group

Infants (<12 months)

• Use 22-25 gauge needles, 7/8-1 inch in length 1, 2
• The anterolateral aspect of the thigh is the preferred injection site, as it provides the largest muscle mass in this age group 1, 2
• Administer at a 90-degree angle into the muscle 1

Children and Adolescents (12 months-18 years)

• Use 22-25 gauge needles, 7/8-1¼ inches in length 1, 2
• The deltoid muscle is preferred if muscle mass is adequate; otherwise use the anterolateral thigh 1, 2
• For toddlers using the thigh, a longer needle (typically 1 inch) is required 1

Adults (>18 years)

• Use 22-25 gauge needles, 1-1½ inches in length 1, 2
• The deltoid muscle is the preferred site for routine intramuscular injections 1, 2
• The anterolateral thigh is an acceptable alternative site 1, 2

Critical Injection Site Selection

Preferred Sites

• Deltoid muscle: The primary site for adults and adolescents with adequate muscle mass 1, 2
• Anterolateral thigh: The preferred site for infants and an acceptable alternative for all ages 1, 2
• Ventrogluteal site: Can be used as an alternative, though less commonly recommended in current guidelines 1

Sites to Avoid

• Never use the buttock routinely due to risk of sciatic nerve injury and decreased vaccine immunogenicity (particularly for hepatitis B and rabies vaccines) 1, 2, 3
• Avoid areas with lipohypertrophy, scars, or tissue abnormalities 2

Technical Requirements

Needle Length Considerations

• The needle must be long enough to penetrate through subcutaneous tissue and reach the muscle mass 1, 2
• The needle should not be so long as to involve underlying nerves, blood vessels, or bone 1, 2
• Individual assessment based on patient age, muscle size, and injection volume is necessary 1

Injection Technique

• Administer at a 90-degree angle to ensure proper muscle penetration 1
• Inject well within the body of a relatively large muscle 1, 4
• Aspiration may help avoid unintentional injection into a blood vessel, though current evidence suggests this may not be necessary 1, 3

Special Considerations for Specific Medications

High-Volume Injections

• When administering large volumes (e.g., 2 grams of ceftriaxone), the dose may need to be divided and administered at two different sites 3
• After reconstitution, ceftriaxone concentrations of 250 mg/mL or 350 mg/mL are appropriate for IM administration 4

Adjuvant-Containing Vaccines

• Vaccines containing adjuvants must be injected into muscle mass 1
• Subcutaneous or intradermal administration of adjuvant-containing vaccines can cause local irritation, induration, skin discoloration, inflammation, and granuloma formation 1

Common Pitfalls to Avoid

• Inadequate needle length: Using needles too short results in subcutaneous rather than intramuscular injection, reducing efficacy and potentially causing local reactions 1
• Wrong site selection: Using the buttock can lead to sciatic nerve injury and decreased drug absorption 1, 3
• Improper angle: Administering at less than 90 degrees may result in subcutaneous injection 1
• Failure to rotate sites: For patients requiring frequent injections, proper site rotation should be maintained 2