This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
True about t 1/2 ? 
Select and explain. 
A. Time required to reduce the plasma conc. to half, B. Zero order kinetics - t 1/2 remains constant, C. First order kinetics - t 1/2 increases, D. Complete drug elimination occurs in 2-3 t 1/2
A: Time required to reduce the plasma conc. to half
Answer: A: Time required to reduce the plasma conc. to half 
Explanation: Ans. is 'a' i.e., Time required to reduce the plasma conc. to half Half life PA It is the time required to reduce the plasma concentration to half (50%) of the original value. It determines the dosing interval and time required to reach the steady state. It is a secondary pharmakokinetic parameter derived from two primary parameters, volume of distribution (Vd) and clearance (CL).