Final answer:
The most used deep intramuscular injection site in adults is the ventrogluteal site. It is safe, accessible, and away from major nerves and blood vessels.
Step-by-step explanation:
The most commonly used deep intramuscular injection site in adults is the ventrogluteal site. It is located on the side of the hip, where the gluteus medius and ventral gluteus muscles are located.
The ventrogluteal site is preferred for its safety and accessibility. It has a good muscle mass and is away from major nerves and blood vessels.
Other deep intramuscular injection sites include the deltoid muscle in the upper arm and the vastus lateralis muscle in the thigh.