Which statement about IV administration is correct regarding absorption?

• A. There is no absorption rate because it goes directly into the bloodstream
• B. Absorption occurs rapidly from the GI tract
• C. Absorption rate is always slower than oral dosing
• D. Absorption is eliminated by first-pass metabolism

Answer: (A)

For IV administration, there is no separate absorption step because the drug is delivered directly into the bloodstream. This means bioavailability is complete (F = 1), and the concept of an absorption rate constant isn’t applicable in the same way as for other routes. If given as a bolus, plasma levels rise immediately to the distribution phase; if given as an infusion, the concentration increases as the drug is infused and distributed, but there’s no GI absorption or first-pass entry to explain the rise.

The other statements don’t fit because absorption from the GI tract only applies to oral or other enteral routes, not IV. Saying the absorption rate occurs rapidly from the GI tract ignores the IV path. Claiming the absorption rate is always slower than oral dosing is incorrect because there’s effectively no absorption step to compare. And suggesting absorption is eliminated by first-pass metabolism is inaccurate for IV, since first-pass metabolism concerns drugs absorbed from the gut entering hepatic circulation before reaching systemic circulation, which IV bypasses entirely.