Which route of administration involves injecting a drug directly into the muscle?

The route of administration that involves injecting a drug directly into the muscle is intramuscular. This method allows for the rapid absorption of the medication into the bloodstream due to the extensive blood supply in muscle tissue. Intramuscular injections are often used for vaccines, hormones, or medications that require quick systemic effects or when a larger volume of medication is needed compared to other routes.

The intramuscular route is effective because it can accommodate larger volumes of fluid than subcutaneous injections, which are limited to smaller doses because of the lesser blood supply in that area. Intravenous administration involves injecting directly into the bloodstream, which provides immediate effects that are different from the sustained release seen with intramuscular routes. Intradermal injections, on the other hand, are delivered into the dermis layer of the skin, which is not suitable for muscular absorption. Therefore, intramuscular administration is specifically designed for delivering medications directly into muscle tissue, which optimizes drug delivery for various therapeutic needs.