This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General pharmacology, Subject name: Pharmacology
Duration of action of i.v. administered drug depends on: 
Select and explain. 
A. Protein binding, B. Clearance, C. Distribution Volume, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Once a drug has gained access to the bloodstream (by iv route), it gets distributed to other tissues that initially had no drug, concentration gradient being in the direction of plasma to tissues. The extent of distribution of a drug depends on its lipid solubility,ionization at physiological pH (a function of its pKa), extent of binding to plasma and tissue proteins, presence of tissue-specific transpoers, differences in regional blood flow, clearance Ref ;KD Tripathi Pharmacology 7th edition (page no;17)