This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pharmacokinetics, Subject name: Pharmacology
A patient presents with nephrotic syndrome and hypoalbuminemia. Protein binding of which drug is not affected: 
Select and explain. 
A. Tolbutamide, B. Morphine, C. Diazepam, D. Valproate
B: Morphine
Answer: B: Morphine 
Explanation: Ans. is 'b' Morphine Nephrotic syndrome leads to loss of proteins so the drugs which are highly bound to protein will be affectednow, have a look at the protein binding of the drugs given in the optionsTolbutamide - 90% (page 277, K.D.T, 4/e)Morphine -30%(p435, K.D.T., 4/e)Diazepam -99% (p-435, K.D. T, 4/e)Valproate -90% (p 388, K.D. T, 4/e)So the drug which is least bound to protein i.e. morphine will be least affected.