Question

What will be the unbound drug concentration if the unbound drug fraction is 0.52 and the total plasma concentration is 140 g/ml?

(a) 80 g/ml

(b) 82.8 g/ml

(c) 70 g/ml

(d) 72.8 g/ml

I have been asked this question during an interview.

This is a very interesting question from Drugs Excretion in portion Prodrugs & Excretion of Drugs of Drug Biotechnology

Answer 1

Correct choice is (d) 72.8 g/ml

Explanation: The fraction of drug bound to plasma proteins can be calculated by the equation fu = Cu/C. Here Fu is fraction of unbound drug and Cu is the concentration of unbound drug in plasma and C is the total plasma concentration of the drug. For the calculation of unbound drug concentration, the equation will be unbound drug fraction * total plasma concentration. Thus the answer will be 0.52*140 = 72.8 g/ml.