Which method is used to inject a drug into the tissue layer between the skin and the muscle?

The correct method for injecting a drug into the tissue layer between the skin and the muscle is subcutaneous (SQ) injection. This technique is utilized to deliver medications into the subcutaneous layer, which allows for slower absorption into the bloodstream compared to intravenous injections. Subcutaneous injections are commonly used for administering vaccines, insulin, and other drugs that require gradual absorption.

This method is advantageous because it is relatively easy to perform and less invasive than intramuscular or intravenous injections. Additionally, the subcutaneous tissue has a good blood supply, which facilitates adequate absorption while minimizing the potential for irritation that might occur with more invasive methods.

In contrast, other methods like intradermal injections target the dermis just beneath the skin surface, which is not suitable for delivering medications intended for deeper tissue absorption. Intravenous injections deliver drugs directly into the bloodstream, providing rapid action but requiring more skill and equipment. Intranasal administration involves delivering medication through the nasal passage, which also serves a different purpose and method of absorption. Therefore, subcutaneous injection is specifically designed for the purpose described in the question.