Which of the following routes of drug administration has the fastest onset of action?

Intravenous administration has the fastest onset of action because drugs are injected directly into the bloodstream, allowing for immediate distribution throughout the body.

a. Oral administration has a slower onset of action because drugs must first pass through the gastrointestinal tract and be absorbed into the bloodstream.

c. Sublingual administration has a faster onset of action than oral administration, but slower than intravenous administration because drugs are absorbed through the mucous membranes under the tongue and must then enter the bloodstream.

d. Topical administration has a slower onset of action because drugs must first pass through the skin or mucous membranes before entering the bloodstream.

Intravenous administration bypasses first-pass metabolism because drugs are injected directly into the bloodstream, avoiding metabolism in the liver before entering the systemic circulation.

a. Oral administration does not bypass first-pass metabolism because drugs must first pass through the liver before entering the systemic circulation.

c. Sublingual administration partially bypasses first-pass metabolism because some of the drugs is absorbed directly into the bloodstream through the mucous membranes under the tongue, but some may still be swallowed and subject to first-pass metabolism.

d. Rectal administration partially bypasses first-pass metabolism because some of the drugs is absorbed directly into the bloodstream through the rectal mucosa, but some may still be subject to first-pass metabolism.