What is the recommended site for intramuscular (IM) promethazine administration?

Recommended Site for Intramuscular Promethazine Administration

Deep intramuscular injection is the preferred and safest route for promethazine administration, with the deltoid muscle recommended for adults and older children, and the anterolateral thigh (vastus lateralis) for infants and younger children. 1

Critical Safety Considerations

The FDA explicitly states that deep intramuscular injection is the preferred parenteral route for promethazine due to severe tissue injury risks associated with other routes 1. This recommendation stems from promethazine's potential to cause:

• Severe chemical irritation and tissue damage regardless of administration route 1
• Tissue necrosis with subcutaneous injection (which is contraindicated) 1
• Gangrene requiring amputation with intra-arterial injection 1
• Thrombophlebitis, venous thrombosis, and abscesses with improper administration 1

Specific Anatomical Sites

Adults and Older Children

The deltoid muscle is the preferred site for intramuscular promethazine in adults and older children. 2

• The intersection between the anteroposterior axillary line and the perpendicular line from the mid-acromion provides the safest deltoid injection site, as it is distant from the axillary nerve and posterior circumflex humeral artery 3
• Needle insertion depth should be 5 mm greater than subcutaneous thickness at a 90° angle 3

Infants and Young Children

The anterolateral aspect of the thigh (vastus lateralis muscle) is the preferred site for infants and young children. 2

• The middle of the vastus lateralis is the safest thigh site due to low risk of vascular or nerve damage 4
• This site avoids the descending branch of the lateral circumflex femoral artery and muscle branches of the femoral nerve, which are present in the rectus femoris 4
• The rectus femoris should be avoided due to major blood vessels observed in the middle of this muscle 4

Administration Technique

Promethazine must be administered as a deep intramuscular injection using proper technique: 1

• Use needle and syringe only (no jet injectors for promethazine) 1
• Ensure deep penetration into muscle tissue to avoid subcutaneous deposition 1
• Aspiration when using the dorsogluteal site is recommended due to proximity to the gluteal artery, though this site is generally not preferred 5
• For deltoid and vastus lateralis sites, aspiration is unnecessary and may increase pain without clinical benefit 5

Critical Pitfalls to Avoid

• Never use subcutaneous injection - this is explicitly contraindicated due to tissue necrosis risk 1
• Never use intra-arterial injection - this causes severe arteriospasm and gangrene 1
• Avoid the dorsogluteal site - while not explicitly contraindicated, the deltoid and vastus lateralis are preferred due to better safety profiles 2, 4
• Do not use the rectus femoris - the vastus lateralis is safer in the thigh due to lower vascular and nerve injury risk 4