What type of injection is classified as a form of systemic drug delivery?

• A. Intravenous
• B. Intramuscular
• C. Subcutaneous
• D. Topical

Answer: (A)

Systemic drug delivery means the drug enters the bloodstream and is distributed throughout the body, not just at the site of administration. An injection into a vein puts the drug directly into the circulatory system, so the entire dose is immediately available in blood, leading to rapid and predictable distribution to distant tissues. In contrast, injections into muscle or under the skin still have to be absorbed into the bloodstream, which slows onset and can vary with tissue conditions, and topical administration mainly acts locally on the surface (though some systemic absorption can occur). That direct, immediate entry into circulation makes intravenous injection the clearest example of systemic drug delivery.