The bioavailability of a drug varies according to its route of administration.

• A. True
• B. False
• C. Sometimes
• D. Not specified

Answer: (A)

Bioavailability is the fraction of an administered dose that reaches the systemic circulation, and it is determined by the route of administration because different routes involve different absorption barriers and first-pass metabolism. Intravenous administration delivers the drug directly into the blood, so its bioavailability is effectively 100%. Other routes must pass through tissues and metabolic processes before entering circulation, which reduces and often delays the amount that becomes available systemically. For example, oral drugs must survive the stomach, be absorbed through the gut, and may be extensively metabolized in the liver before reaching the bloodstream, leading to lower and more variable bioavailability. Other routes like intramuscular, subcutaneous, inhalation, or transdermal delivery have their own absorption characteristics that affect how much of the dose becomes available in the circulation. Therefore, the statement is true: bioavailability varies with the route of administration. The other options don’t fit because they either ignore this route-related difference or imply inconsistency where the general principle is that route influences bioavailability.