Question

In a graph of renal clearance versus plasma drug concentration, which kind of drug will give the below shown curve?

(a) Drug excreted only by filtration

(b) Drug filtered and actively reabsorbed

(c) Drug filtered as well as actively secreted

(d) Drug reabsorbed actively

I have been asked this question in an online interview.

This intriguing question originated from Drugs Excretion in section Prodrugs & Excretion of Drugs of Drug Biotechnology

Answer 1

Correct answer is (b) Drug filtered and actively reabsorbed

The explanation: The drugs which are secreted or reabsorbed, the rate increases with an increase in plasma concentration to a point where saturation occurs. Drugs which are actively reabsorbed, excretion is negligible at low plasma concentration. These agents are excreted in urine when their glomerular filtrate concentration exceeds the active reabsorption capacity e.g. glucose.