Author Question: Which one of the following effects is likely to accompany presystemic biotransformation of a drug? ... (Read 55 times)

mia · **on:** Jul 23, 2018

Which one of the following effects is likely to accompany presystemic biotransformation of a drug?

a. Decreased cardiac output
b. First-pass effect in the liver
c. Protein binding in the bloodstream
d. Tissue binding in a body compartment

Question 2

A patient is receiving supplemental doses of vitamin D. Which mechanism of transport applies to absorption of this drug?

a. Simple passive diffusion
b. Filtration
c. Pinocytosis
d. Active transport

LP · **Reply #1 on:** Jul 23, 2018

Answer to Question 1

ANS: B
Drugs may be biotransformed, usually to inactive metabolites, before reaching the systemic cir-culation. Orally administered drugs are transformed in the gastrointestinal (GI) tract by acids, digestive enzymes, bacterial action, and enzymes in the cells of the intestinal walls. Venous blood from the GI tract (except the mouth and the rectum) passes through the liver via the portal sys-tem before entering systemic circulation. Therefore drugs that are highly cleared by the liver will undergo considerable biotransformation before entering systemic circulation. This phenomenon is known as the first-pass effect.

Answer to Question 2

ANS: C
Fat-soluble vitamins (A, D, E, K) are absorbed by pinocytosis. In this process, the cell wall in-vaginates, forms a vacuole for drug transport, breaks off, and moves into the cell.