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
Drug excretion through kidney depends on all, EXCEPT 
Select and explain. 
A. High blood flow in kidney, B. Molecular weight of drug, C. Lipid solubility of drug, D. Plasma protein binding of drug
B: Molecular weight of drug
Answer: B: Molecular weight of drug 
Explanation: Ans. is 'b' molecular weight of the drug The amount of drug excreted by the kidney depends on 3 factors:- Glomerular filtration, tubular reabsorption, tubular secretion.Glomerular filtrationIt depends upon Plasma protein binding - Only unbound form is excreted. Renal blood flow - G.F.R. increase with increase in renal blood flow.Tubular reabsorptionThis depends uponLipid solubility of the drug - Nonlipid soluble drugs are excreted more Ionization of the drug - highly ionized drugs are excreted moreTubular secretionIt is the active transfer of organic acids and bases by two separate nonspecific mechanisms