The Z-track method of I.M. injection prevents leakage, or tracking, into the subcutaneous tissue. It’s typically used to administer drugs that irritate and discolor subcutaneous tissue, primarily iron preparations such as iron dextran. It may also be used in an elderly patient who has a decreased muscle mass. Lateral displacement of the skin during the injection helps to seal the drug in the muscle.

Discomfort and tissue irritation may result from drug leakage into subcutaneous tissue. Failure to rotate sites in patients who require repeated injections can interfere with the absorption of medication. Unabsorbed medications may build up in deposits that can reduce the desired pharmacologic effect and may lead to abscess formation or tissue fibrosis.