Which route is described as the least effective way to administer drugs?

• A. IV
• B. Oral
• C. Topical
• D. Sublingual

Answer: (C)

The main idea is how much of a drug actually reaches the bloodstream and becomes available to exert an effect. Routes differ in this bioavailability. Intravenous administration puts the drug directly into the circulation, so the entire dose is available immediately. Sublingual administration allows the drug to be absorbed through the oral mucosa quickly and without being blasted by the stomach or liver, giving fast and fairly reliable systemic levels. Oral dosing goes through the gut and then the liver, where some of the drug is lost to metabolism before it reaches the bloodstream, so absorption is slower and more variable. Topical administration is designed for local action on the skin or mucous membranes; the barrier nature of the skin and mucosa means only a small, often variable amount gets absorbed systemically. Because of that local focus and limited, inconsistent systemic absorption, topical is the least effective route for achieving systemic drug effects, even though it can be very useful when a local effect is desired.