CRDTS Local Anesthesia Practice Test

Local anesthetics work by diffusing from the injection site through surrounding tissues to reach the nerve membrane and block sodium channels. Placing the drug in the soft tissue just under the mucosa—the subcutaneous layer—puts it in close proximity to the nerve, allowing diffusion into the perineural space and onto the nerve fibers to produce numbness. This subcutaneous depot balances diffusion distance with adequate tissue containment, giving reliable onset and duration. Depositing into muscle would place the drug in more vascular tissue, leading to faster systemic absorption and less effective local blockade. Injection into bone (intraosseous) or directly into a vein is not how standard nerve blocks are achieved and carries different risks. So, most local anesthetics are deposited in the subcutaneous tissue surrounding the target nerve.