What is the preferred site for administration of intramuscular injections in adults?

The preferred site for administration of intramuscular injections in adults is indeed the deltoid or vastus lateralis muscles. The deltoid muscle is commonly used for vaccinations and other medications due to its accessibility and the relatively low volume of medication typically administered, which is usually up to 1 mL. Its location on the upper arm allows for easy access and minimizes discomfort for the patient.

On the other hand, the vastus lateralis muscle, located in the thigh, is recommended primarily for larger volume injections (up to 3 mL) and for pediatric patients. This site is also advantageous because it is away from major nerves and blood vessels, reducing the risk of complications.

Other sites, such as the ventrogluteal muscle and gluteal muscle, can be used but are less preferred due to their proximity to the sciatic nerve and larger blood vessels, thus presenting a higher risk of injury. Subcutaneous tissue is not appropriate for intramuscular injections as it does not have the vascularity required for effective absorption of medications meant for intramuscular delivery.

By selecting the deltoid or vastus lateralis, healthcare providers ensure a balance of safety, efficacy, and patient comfort when administering intramuscular injections.