Which route delivers medication directly into the bone marrow and may require drilling through the outer bone layer?

• A. Intraosseous injection
• B. Intramuscular injection
• C. Intravenous injection
• D. Transdermal

Answer: (A)

Delivering medication directly into the bone marrow is the intraosseous route. It bypasses the skin and subcutaneous tissues and places the drug into the medullary cavity, which is highly vascular and quickly communicates with the central circulation. Because the cortex of the bone can be hard, the technique may involve drilling or using a special needle to penetrate the outer bone layer and access the marrow space. Once inside, meds are absorbed rapidly, making this route especially useful when IV access is difficult or time-pressured.

Intramuscular injections go into muscle tissue and absorb more slowly and variably. Intravenous injections go directly into a vein, not into bone marrow. Transdermal routes deliver drugs through the skin over a longer period and are not used for rapid emergency access.