Certified Medical Assistant Practice Exam

The most common intramuscular injection site for infants less than seven months old is the vastus lateralis. This site is located on the lateral side of the thigh and is preferred for several reasons.

First, the vastus lateralis is well-developed in infants, making it both safe and effective for administering vaccines or medications. Infants have less muscle mass overall compared to older children and adults, and the vastus lateralis stands out as the site with the most muscle bulk in this age group.

Second, this location minimizes the risk of injury to important nerves and blood vessels, which is a significant concern when administering intramuscular injections. The other sites, such as the deltoid and gluteus maximus, are not as suitable for infants due to the limited muscle size and potential risk of injury.

Additionally, the gastrocnemius muscle, located in the calf, is not typically used for intramuscular injections due to its smaller size and deeper positioning, which may increase the risk of complications. Given these considerations, the vastus lateralis is the optimal choice for administering intramuscular injections in infants under seven months.