Which injection is delivered directly into a vein?

• A. Intramuscular injection
• B. Intravenous injection
• C. Subcutaneous injection
• D. Oral administration

Answer: (B)

Delivering a substance directly into a vein means it enters the bloodstream immediately. This route, intravenous administration, has the fastest onset because the medication bypasses absorption barriers and goes straight into circulation. It’s used when a rapid effect is needed or when precise control of dosing is important.

In contrast, intramuscular injections place the drug into muscle tissue where it must diffuse into blood vessels, giving a quicker but slower absorption than IV. Subcutaneous delivery goes into the fat beneath the skin, resulting in even slower absorption. Oral administration requires the drug to pass through the digestive system and liver before reaching the bloodstream, which delays and may reduce how much of the drug becomes available systemically. Therefore, the injection delivered directly into a vein is intravenous administration.